Next Article in Journal
Magnetically Recoverable Magnetite/Gold Catalyst Stabilized by Poly(N-vinyl-2-pyrrolidone) for Aerobic Oxidation of Alcohols
Next Article in Special Issue
Synthesis of New Visnagen and Khellin Furochromone Pyrimidine Derivatives and Their Anti-Inflammatory and Analgesic Activity
Previous Article in Journal
Antimalarial Activity of Methanolic Leaf Extract of Piper betle L.
Previous Article in Special Issue
Application of Cycloaddition Reactions to the Syntheses of Novel Boron Compounds
 
 
Search for Articles:
Title / Keyword
Author / Affiliation / Email
Journal
Article Type
 
 
Advanced Search
 
Section
Special Issue
Volume
Issue
Number
Page
 
Journals
Molecules
Volume 16
Issue 1
10.3390/molecules16010119
molecules-logo
Submit to this Journal Review for this Journal Propose a Special Issue
► Article Menu

Article Menu

share Share announcement Help format_quote Cite question_answer Discuss in SciProfiles thumb_up
...
Endorse textsms
...
Comment
first_page
settings
Order Article Reprints
Font Type:
Arial Georgia Verdana
Font Size:
Aa Aa Aa
Line Spacing:
Column Width:
Background:
Review

Solid-State [2+2] Photodimerization and Photopolymerization of α,ω-Diarylpolyene Monomers: Effective Utilization of Noncovalent Intermolecular Interactions in Crystals

by
Yoriko Sonoda
Photonics Research Institute, National Institute of Advanced Industrial Science and Technology (AIST), Higashi 1-1-1, Tsukuba, Ibaraki 305-8565, Japan
Molecules 2011, 16(1), 119-148; https://doi.org/10.3390/molecules16010119
Submission received: 25 November 2010 / Revised: 17 December 2010 / Accepted: 24 December 2010 / Published: 28 December 2010
(This article belongs to the Special Issue Cycloaddition Reactions in Organic Synthesis)
Browse Figures
Versions Notes

Abstract

:
[2+2] Photocycloaddition of olefins is a very useful reaction in synthetic organic chemistry to obtain cyclobutane-containing molecules, which are almost inaccessible by other methods. The reaction, when performed in the crystalline state, occurs more efficiently and selectively than in homogeneous solution due to tight and regular molecular arrangement in the crystal state. Despite numerous examples for the solid-state [2+2] photodimerization of monoenes, however, it is still a challenge to prepare not only dimers but also higher oligomers and polymers from conjugated polyenes, which have multiple reactive double bonds in a molecule. In our recent studies of the solid-state photoreactions of α,ω-diarylpolyenes, noncovalent intermolecular interactions in crystals were effectively utilized to prealign molecules in stacking arrangements, suitable for the [2+2] reaction. With appropriate ring-substituents, [2+2] photodimerization and photopolymerization of the polyenes took place, although the degree of polymerization was relatively low. This review will describe the details of these reactions.

Graphical Abstract

1. Introduction

[2+2] Photocycloaddition is one of the best known reactions of olefins in solid-state organic photochemistry [1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16]. By using the reaction, cyclobutane molecules, almost inaccessible by other synthetic methods, are easily obtained in high or at least reasonably good yields. The reaction, when performed in the crystalline state, occurs more efficiently and selectively than in homogeneous solution due to the tight and regular molecular arrangement found in crystals. It is often observed that the photoproducts in the solid state are entirely different from those in solution. Further, it has recently attracted increasing attention as one of the best suited reactions for 'green chemistry', because the reaction is 'solvent-less' in nature [14,15,16,17]. Even for two-component reactions, the mixing and grinding the reactant solids induce 'mechanochemical self-assembly' to lead high reaction efficiency without using any solvents [18,19,20,21,22]. In addition, only light irradiation is needed for the reaction to take place. No other energy supply such as heating equipment is required, as the photoreaction usually proceeds at or below room temperature.
During 1960-1970s, Schmidt and co-workers thoroughly and systematically studied the solid-state [2+2] photocycloaddition of cinnamic acids (CAs) [1,2,23,24,25]. From crystallographic investigations 'topochemical rules', which connect the configuration of the product and crystal structure of the reactant, were revealed [6,9,23]. It is well-known that for topochemical [2+2] photocycloaddition, the distances between the potentially reactive double bonds should be less than ca. 4.2 Å ('Schmidt's rule') [1,2,25]. Since the pioneering work of Schmidt et al., numerous examples of the solid-state [2+2] photo-dimerization of olefins, mostly monoenes, have been reported. Up to now, a number of strategies have been employed to prealign molecules in stacking arrangements favorable for the [2+2] reaction. These include intramolecular substitution to control intermolecular interactions between reactant olefins in crystals [11,26,27,28,29,30,31,32], inclusion within host structures [11,14,15,16], and cocrystallization with hydrogen-bond templates [33,34,35]. Coordination to a metal is also used to preorganize molecules for thereaction [36,37]. The use of tetranuclear rectangle macrocycles is an interesting new approach [38,39,40].
The [2+2] cycloaddition of molecules having two or more potentially reactive double bonds, such as diolefins and conjugated polyenes, can be a polymerization reaction. As for the reactions of aromatic diolefins, the [2+2] photopolymerization of distyrylpyrazines and phenylene diacrylates took place topochemically to afford highly crystalline polymers [41,42]. The reaction is known as 'four-center type photopolymerization'. For conjugated polyenes, however, it is still a challenge to prepare not only dimers but also higher oligomers and polymers. This is probably due to highly flexible polyenic chains even in the solid state. Although the hydrogen-bond templates have been successfully used to prepare ladder-shaped [2+2] dimers from conjugated dienes and trienes (in 100% yield), the reactions did not afford higher molecular weight (MW) products [33,34,35].
In our recent studies on the solid-state photoreactions of ring-substituted α,ω-diphenylpolyenes (Figure 1), noncovalent intermolecular interactions in crystals were effectively utilized to prealign molecules in stacking arrangements suitable for the [2+2] reaction. Unsubstituted parents of this class of molecules were all photochemically inert due to unfavorable crystal packing for the reaction. With appropriate substituents, however, [2+2] photodimerization and photopolymerization of the polyenes took place in the crystalline state. This review will mainly describe the photoreactions of ring-substituted (E,E,E)-1,6-diphenyl-1,3,5-hexatrienes (3; DPHs), and compare them with those of ring-substituted (E)-CAs and (E,E)-1,4-diphenyl-1,3-butadienes (2; DPBs).
Molecules 16 00119 g001 550
Figure 1. Chemical structures of α,ω-diphenylpolyenes 1-3.
Figure 1. Chemical structures of α,ω-diphenylpolyenes 1-3.
Molecules 16 00119 g001

2. [2+2] Photodimerization and Photopolymerization of α,ω-Diarylpolyenes

Unsubstituted α,ω-diphenylpolyenes, (E)-stilbene 1, (E,E)-DPB, and (E,E,E)-DPH, were all photochemically stable in the solid state [43,44,45]. The molecules in the crystal structure of(E,E)-DPB [46,47] were arranged in a 'herringbone' pattern [48,49]. The nonparallel arrangement of double bonds of adjacent molecules was obviously unsuitable for the [2+2] cycloaddition. Also in (E,E,E)-DPH crystal, the molecular arrangement was unfavorable for the reaction, and the double bond distance for the nearest stacking molecules was 7.730 Å (= a) [50]. However, introduction of appropriate ring-substituents into the benzene rings of DPB and DPH led to π-stacked arrangements in crystals favorable for the [2+2] reaction.

2.1. Cyano Substitution

4,4'-Dicyano-substituted (E,E,E)-DPH 4 underwent crystalline-state [2+2] photocycloaddition at the terminal double bonds of the triene to give mirror-symmetric dimer 5, trimers (6; the most plausible structure of the main trimer) and oligomers (Scheme 1) [45]. In the solid state, no Z-E geometrical photoisomerization was observed, in contrast to highly efficient and selective EEE→ZEE isomerization in diluted solution [51,52].
Molecules 16 00119 g013 550
Scheme 1. [2+2] Photodimerization and photopolymerization of 4.
Scheme 1. [2+2] Photodimerization and photopolymerization of 4.
Molecules 16 00119 g013
In the crystal structure [53], molecules were linked by CH···N hydrogen bonding [54,55,56,57,58] and CN···CN dipole-dipole interactions [58] to make a tape (Figure 2). The tapes were further linked by CH···N hydrogen bonds to make a sheet. The molecules were π-stacked with the distance between the reactive double bonds of 3.928 Å, reasonably close each other. Thus the double bond distance of 7.73 Å in unsubstituted DPH [50] largely decreased to 3.93 Å in 4, indicating the remarkable effect of cyano substitution. Considerably strong face-to-face interactions between π-orbitals of the molecules were evidenced by the observation of excimer fluorescence from the crystal [45,59]. The [2+2] photoreaction of 4 is considered to proceed via the excimer(s).
Molecules 16 00119 g002 550
Figure 2. CH···N hydrogen bonding and CN···CN dipole-dipole interactions incrystal 4.
Figure 2. CH···N hydrogen bonding and CN···CN dipole-dipole interactions incrystal 4.
Molecules 16 00119 g002
Interestingly, the very similar structural motif shown in Figure 2 has been observed in the crystal structure of 4-cyano-substituted (E)-CA [58]. The centro-symmetric carboxylic dimers of 4-cyano CA were organized into molecular sheets utilizing CN···CN dipole interactions and weaker forces such as CH···N and CH···O hydrogen bonds. The molecules were stacked with the double bond center-to-center distance of ca. 3.7-3.8 Å. Despite a large offset for the double bonds of stacking two molecules, the crystal was [2+2] photoreactive to give a mirror-symmetric dimer in 94% yield.

2.2. Formyl Substitution

4-Formyl substitution on the benzene rings of (E,E,E)-DPH also induced the [2+2] photocycloaddition of hexatriene double bonds. Irradiation of 7 gave mirror-symmetric dimer 8 (Scheme 2) [45]. Crystal 7 was less reactive than 4 and the yield of higher oligomers than dimer was low. In diluted solution, 7 underwent efficient Z-E photoisomerization, whose regioselectivity (EEE→ZEE vs. EEE→EZE) depended on the spin multiplicity of the excited states involved in the reaction [60,61,62] (Scheme 3). While in the solid state, no Z-E isomerization was observed.
CH···O-type hydrogen bonds [57,63,64,65,66,67,68] were observed between the formyl groups of the neighboring molecules in crystal [53], in agreement with the results of IR and 13C CP/MAS NMR spectral measurements [45]. Molecules were π-stacked with the distance between the two reactive double bonds of 3.926 Å. As in 4, the solid-state excimer fluorescence was observed in 7, indicative of the presence of intermolecular π-orbital interactions of considerable strength [45,59].
Molecules 16 00119 g014 550
Scheme 2. [2+2] Photodimerization of 7 in the crystalline state.
Scheme 2. [2+2] Photodimerization of 7 in the crystalline state.
Molecules 16 00119 g014
Molecules 16 00119 g015 550
Scheme 3. Regioselective Z-E photoisomerization of 7 in solution.
Scheme 3. Regioselective Z-E photoisomerization of 7 in solution.
Molecules 16 00119 g015
4-Formyl-substituted (E)-CA also underwent [2+2] cycloaddition in the solid state to give a mirror-symmetric photodimer in a quantitative yield [69,70,71]. The molecules formed centro-symmetric carboxylic dimers, which piled up to form a plane-to-plane parallel stack. Although the shortest intermolecular distance between the reactive double bonds (4.825 Å) was significantly longer than the Schmidt's criterion of 4.2 Å, the plane-to-plane perpendicular distance between reactive molecules (3.388 Å) was fairly short, thus making the molecule [2+2] photoreactive [72].
As seen, the cyano and formyl substitution was both effective to prealign molecules for the [2+2] cycloaddition of (E,E,E)-DPH. It should be noted that molecules in the photoreactive crystals 4 and 7 are joined through relatively weak intermolecular interactions such as CH···N and CH···O hydrogen bonds [45].

2.3. Nitro Substitution

As in 7, weak CH···O-type hydrogen bonds [68,73,74] were observed in the crystal structure of 9 (Scheme 4) [75]. The molecular sheets formed by the CH···O hydrogen bonds were linked by intermolecular N···O dipole interactions and aromatic π-π stacking interactions into a three-dimensional framework. The double bond distance for the stacking molecules was 3.871 Å, similar to or even slightly shorter than those for the [2+2] photoreactive crystals of 4 and 7. Contrary to expectation, however, 9 was photochemically very stable in the crystalline state [45,76] as in solution [52].
Consistently, unlike 4 and 7, the solid-state fluorescence of 9 originated not from excimeric but from monomeric species [76]. This indicates the absence of strong π-orbital-π-orbital interactions between the stacking molecules in the excited state, although they are in close proximity in the ground state.
Molecules 16 00119 g016 550
Scheme 4. Stacking two molecules in photostable crystal 9.
Scheme 4. Stacking two molecules in photostable crystal 9.
Molecules 16 00119 g016

2.4. Alkoxy-Nitro (Donor-Acceptor) Substitution

Cocrystallization of 2,5-dimethoxy- and 3,5-dinitro-substituted (E)-CAs, 10 and 11 respectively, led to π-stacked molecular arrangements as a result of OH···O and CH···O hydrogen bonding, and donor-acceptor charge transfer (CT)-type stacking interactions [77,78]. The resulting 1:1 cocrystal 10/11 photoreacted to give 12 (Scheme 5).
Molecules 16 00119 g017 550
Scheme 5. [2+2] Photocycloaddition of 10 and 11 in 1:1 cocrystal 10/11.
Scheme 5. [2+2] Photocycloaddition of 10 and 11 in 1:1 cocrystal 10/11.
Molecules 16 00119 g017
Unfortunately, however, an attempt to cocrystallize 4,4'-dinitro DPH 9 and 4,4'-dimethoxy-substituted (E,E,E)-DPH was unsuccessful; from the 1:1 mixture of the two derivatives in acetonitrile, only single crystals of 9 were grown out from the solution.
The crystal of (E,E)-1-(2-methoxyphenyl)-4-(4-nitrophenyl)-1,3-butadiene 13 was irradiated to give head-to-tail dimer 14 (Scheme 6) [79]. Similarly, irradiation of donor-acceptor-substituted (E,E)-diene ester 15 gave dimer 16 (Scheme 7) [80]. In the crystal structure of 15, the double bonds that reacted to form 16 were close to one another with the distances of 3.9-4.0 Å, and were arranged in a head-to-tail manner with only a slight offset.
Molecules 16 00119 g018 550
Scheme 6. [2+2] Photodimerization of 13.
Scheme 6. [2+2] Photodimerization of 13.
Molecules 16 00119 g018
Molecules 16 00119 g019 550
Scheme 7. [2+2] Photodimerization of 15.
Scheme 7. [2+2] Photodimerization of 15.
Molecules 16 00119 g019
For a series of (E,E,E)-1-(4-alkoxyphenyl)-6-(4-nitrophenyl)-1,3,5-hexatrienes 17-20 (Figure 3), the relationship between crystal structure and photophysical/photochemical properties was systematically investigated [81].
Molecules 16 00119 g003 550
Figure 3. Chemical structures of alkoxy-nitro-substituted (E,E,E)-DPHs 17-20.
Figure 3. Chemical structures of alkoxy-nitro-substituted (E,E,E)-DPHs 17-20.
Molecules 16 00119 g003
In the crystal structure of 20, the O atom of the nitro group was in close contact with a neighboring H atom of the nitrophenyl ring at the ortho position relative to the nitro group to form a weak CH···O hydrogen bond [68,73,74]. A pair of this type of hydrogen bonds formed a hexagonal pattern between adjacent two molecules to make a tape (Figure 4) [55,57,73]. The molecular tapes were π-stacked with the double bond distance of 3.862 Å (Scheme 8). Also, molecules in crystal 18 were shown by powder X-ray diffraction (XRD) analysis to be arranged in a π-stacked fashion. While in crystals 17 and 19, molecules were arranged in a herringbone pattern. Therefore at least 18 and 20 were expected to be [2+2] photoreactive. Actually, however, 17-20 were all photochemically stable in the solid state. The results were consistent with the fact that all four molecules exhibited solid-state fluorescence of monomeric origin but no excimer fluorescence. They underwent Z-E photoisomerization in low polar solvents [82], but did not isomerize in the crystalline state.
Molecules 16 00119 g004 550
Figure 4. A hexagonal pattern formed by CH···O hydrogen bonds in crystal 20.
Figure 4. A hexagonal pattern formed by CH···O hydrogen bonds in crystal 20.
Molecules 16 00119 g004
Thus, as a consequence of attractive CT interactions, the donor-acceptor (E,E)-DPB 13 and related molecule 15 were organized into π-stacked structures. The resulting crystals were [2+2] photoreactive, as expected. For donor-acceptor (E,E,E)-DPHs 17-20, on the other hand, the ring-substitution was not effective in all cases to steer stacking molecular arrangements.
Molecules 16 00119 g020 550
Scheme 8. Stacking two molecules in photostable crystal 20.
Scheme 8. Stacking two molecules in photostable crystal 20.
Molecules 16 00119 g020
The packing patterns of molecules (i.e., herringbone and π-stacked) depended clearly on a slight difference in molecular structure such as the alkoxy chain length. This suggests that the two packing patterns of these trienes are nearly isoenergetic. It is likely that, as for the larger π-system of DPH than that of DPB, the face-to-face stacking arrangements are considerably stabilized by CT (and π-π) interactions, but significantly destabilized by π-π repulsion [81]. Further, no photoreactivity of crystals 18 and 20 was rather unexpected, considering that diene crystals 13 and 15 were photoreactive. This may possibly be due to the difference in the magnitude of π-orbital interactions in the excited state for the diene and triene systems.

2.5. Halogen Substitution

2.5.1. Chlorine substitution

It is well-known that chlorine substitution is effective to steer stacking arrangements suitable for [2+2] photocycloaddition of aromatic olefins [6,9,63]. The effects are mainly based on the attractive Cl···Cl interactions [83,84,85,86,87]. Typical examples include 2,4- and 2,6-dichloro substitution for (E)-CA [24,88], (E)-stilbene [89,90], (E,E)-DPB and related molecules [43,91,92,93].
Irradiation of 2,6-dichloro-substituted (E,E)-DPB 21 gave mirror-symmetric dimer 22 in high yield (Scheme 9). Excimer emission in the solid state was observed in this case [43,93]. Of the two possible isomers 22 and 23, only one kind of dimer 22 was formed from 21, which was explained in terms of twisting of 2,6-dichlorophenyl ring from the butadiene plane [43] and intramolecular conformational changes in the excimer formation [93].
Molecules 16 00119 g021 550
Scheme 9. [2+2] Photodimerization of 21.
Scheme 9. [2+2] Photodimerization of 21.
Molecules 16 00119 g021
In the crystal structure of 2,2',4,4'-tetrachloro-substituted (E,E,E)-DPH 24, molecules were linked via Cl···Cl interactions with the shortest intermolecular Cl···Cl distance of 3.514 Å (Scheme 10) [94]. The molecules were further joined through π-π stacking interactions with the double bond distance of 3.950 Å. The closely stacked molecular arrangement was clearly a result of chlorine ring-substitution. Despite the relatively short distance between double bonds, however, 24 was unreactive in the solid state [45]. No observation of excimer fluorescence suggests the presence of only weak orbital-orbital interactions between the stacking molecules [59].
Molecules 16 00119 g022 550
Scheme 10. Molecular arrangements and multiple Cl···Cl interactions in photostablecrystal 24.
Scheme 10. Molecular arrangements and multiple Cl···Cl interactions in photostablecrystal 24.
Molecules 16 00119 g022
The photostability of 24 may at least partially be due to multiple Cl···Cl interactions between adjacent molecules, which will prevent easy atomic and molecular movements required by the [2+2] reaction in crystal [94].

2.5.2. Fluorine substitution

It has recently been recognized that fluorine substitution [67,68,95,96] is probably more useful than chlorine substitution for constructing [2+2] photoreactive crystals [97,98,99,100,101,102,103]. In particular, noncovalent intermolecular interaction between C6F5 and C6H5 rings is known to be strongly attractive [104,105,106,107,108,109]. The interaction is widely used in crystal engineering as a strong supramolecular synthon to steer face-to-face stacking arrangements of aromatic molecules [110,111,112,113,114,115,116,117,118,119]. It can be utilized to prealign molecules not only for [2+2] photocycloaddition of olefins [120,121,122,123], but also for photo-polymerization of diacetylenes in the crystalline state [124,125].
The C6F5···C6H5 interaction induced [2+2] cycloaddition of (E)-CA, (E)-stilbene, and (E,E)-distyrylbenzene molecules [120]. Irradiation of center-ring perfluorinated (E,E)-distyrylbenzene 25 yielded a white powder that was virtually insoluble in common organic solvents. The toluene-soluble part of the product was shown by GPC analysis to be an oligomeric mixture (predominantly dimer to tetramer) (26; the proposed structure) (Scheme 11).
(E,E)-1-Pentafluorophenyl-4-phenyl-1,3-butadiene 27 underwent double [2+2] photocycloaddition in the solid state to afford ladder-shaped dimer 28 (Scheme 12) [121]. Considering no reactivity of parent DPB, it is clear that perfluorination of the benzene ring brings remarkably the reactant molecules into head-to-tail stacking arrangement in the crystal lattice. For the centro-symmetrically related reactive double bonds, the center-to-center distances were reported to be 3.724 and 3.895 Å. The low yield of photoproduct was ascribed to the stepwise reaction mechanism for the dimerization.
For a series of ring-fluorinated (E,E,E)-DPHs 29-33 (Figure 5), the relationship between crystal structure and photophysical/photochemical properties was systematically investigated [122]. Fluorination at 4-, 2,4-, or 2,4,6-positions of the two terminal benzene rings of (E,E,E)-DPH was ineffective to induce [2+2] photocycloaddition. In the crystal structure, molecules 29 were arranged in a typical herringbone fashion, unfavorable for the photoreaction. Although molecules 30 and 31 were π-stacked in the lattice, the planes of the nearest two molecules were largely offset along the short molecular axes. For the nearest stacking molecules, the double bond distances [7.515 Å (=c) for 30 and 7.217 Å (=b) for 31] were too large for the reaction to occur.
Molecules 16 00119 g023 550
Scheme 11. [2+2] Photodimerization and photopolymerization of 25.
Scheme 11. [2+2] Photodimerization and photopolymerization of 25.
Molecules 16 00119 g023
Molecules 16 00119 g024 550
Scheme 12. Double [2+2] photocycloaddition dimerization of 27.
Scheme 12. Double [2+2] photocycloaddition dimerization of 27.
Molecules 16 00119 g024
Molecules 16 00119 g005 550
Figure 5. Chemical structures of fluorinated (E,E,E)-DPHs 29-33.
Figure 5. Chemical structures of fluorinated (E,E,E)-DPHs 29-33.
Molecules 16 00119 g005
On the other hand, crystal 32 and 1:1 cocrystal 3/33 (Figure 6) were highly photoreactive. The [2+2] reaction of 32, in particular, was much efficient compared to those of typical organic solids. The conversion reached 100% after only 3 h-irradiation. The photoproduct was a mixture of dimer 34, trimers (35; the most plausible structure of the main trimer), and higher oligomers, all soluble in common organic solvents such as dichloromethane and acetonitrile (Scheme 13). Although the photoreaction in solution occurred inefficiently to give a mixture of several kinds of dimers, only one kind of dimer (and its mirror-image) was predominantly formed in the solid state [123]. Unlike in crystal 27 [121], the double [2+2] cycloaddition giving a ladder-shaped dimer did not take place in 32. The photoreaction of cocrystal 3/33 was similar but somewhat less efficient than the reaction of 32 [123].
Molecules 16 00119 g006 550
Figure 6. Stacking molecular arrangements in crystal 32 and 3/33.
Figure 6. Stacking molecular arrangements in crystal 32 and 3/33.
Molecules 16 00119 g006
Molecules 16 00119 g025 550
Scheme 13. [2+2] Photodimerization and photopolymerization of 32.
Scheme 13. [2+2] Photodimerization and photopolymerization of 32.
Molecules 16 00119 g025
As a result of effective C6F5···C6H5 interactions, the molecules in crystals 32 and 3/33 were very similarly arranged in a π-stacking fashion (Figure 6) [122]. The double bond distances were 4.067 and 4.119 Å for 32, and 4.098 and 4.126 Å for 3/33. The reaction efficiency and the highest MW of the photoproduct for 32 and 3/33 were considerably enhanced when compared to those for 4 and 7, although the double bond distances of the stacked molecules in the original structures were not greatly different for these crystals. This suggests that the C6F5···C6H5 stacking interactions are more effective than the π-π stacking interactions to keep molecules in nearly face-to-face arrangements during the [2+2] photoreaction, in which the bulky cyclobutane products will destroy the initially ordered molecular alignments.
Figure 7(A) shows the changes in solid-state absorption spectra of 32 obtained by Kubelka/Munk (K/M) conversion of the diffuse reflectance spectra during the photoreaction. On irradiation, the absorption band of the starting monomer around 400 nm decreased in intensity, and a new band of the dimeric and polymeric photoproducts was growing up around 325 nm. The large blue-shift of 70-80 nm in the absorption indicates the destruction of DPH π-conjugated system by the formation of aliphatic cyclobutane ring. The spectroscopic changes during the reaction of 3/33 were fundamentally similar (Figure 7(B)). The initially observed band around 410 nm decreased in intensity on irradiation, and the product band newly appeared around 320 nm.
Molecules 16 00119 g007 550
Figure 7. (A) Solid-state absorption spectra of 32 (a) before and after irradiation for (b) 15, (c) 30, (d) 60, and (e) 90 min;(B) Solid-state absorption spectra of 3/33 (a) before and after irradiation for (b) 60,(c) 120, and (d) 240 min.
Figure 7. (A) Solid-state absorption spectra of 32 (a) before and after irradiation for (b) 15, (c) 30, (d) 60, and (e) 90 min;(B) Solid-state absorption spectra of 3/33 (a) before and after irradiation for (b) 60,(c) 120, and (d) 240 min.
Molecules 16 00119 g007
Figure 8(A) shows the changes in the solid-state fluorescence spectra during the photoreaction of 32. Before irradiation, the weak emission band due to excimeric species was observed around 525 nm, indicating strong π-orbital interactions between stacked molecules in the original crystal [122]. On irradiation, a new band centered at 495 nm was rapidly growing. This blue-shifted strong emission originated probably from unreacted monomers that were isolated in the crystal lattice with the progress of the reaction. When irradiated further, the intensity of the monomer emission gradually decreased, and finally a broad band remained only weakly around 500 nm. This suggests that the cyclobutane products are practically nonfluorescent. Similar spectral changes were observed for 3/33 (Figure 8(B)).
Molecules 16 00119 g008 550
Figure 8. (A) Solid-state fluorescence spectra of 32 (a) before and after irradiation for (b)10, (c) 20, (d) 60, and (e) 120 min; (B) Solid-state fluorescence spectra of 3/33 (a) before and after irradiation for (b)10, (c) 20, (d) 60, and (e) 120 min.
Figure 8. (A) Solid-state fluorescence spectra of 32 (a) before and after irradiation for (b)10, (c) 20, (d) 60, and (e) 120 min; (B) Solid-state fluorescence spectra of 3/33 (a) before and after irradiation for (b)10, (c) 20, (d) 60, and (e) 120 min.
Molecules 16 00119 g008
In this case, the weak fluorescence band initially observed around 565 nm was assigned to the emission from molecular aggregates [122]. Whereas, the band around 490 nm growing on irradiation would be due to unreacted monomers isolated in the lattice. For 32 and 3/33, the solid-state absorption and emission spectra thus dramatically changed before and after irradiation.
Figure 9 shows the changes in the polarizing optical micrographs of cocrystal 3/33 during the photoreaction. The results can be compared with those of crystal 32 reported previously [123]. On irradiation, stripe-like microstructures formed very rapidly on the crystal surface. The formation of such microstructures was not observed for 32. When irradiated further, the structures gradually disappeared and a transparent part was slowly growing up from the edge of the crystal. When the reaction was completed after 5 h, the crystal became almost completely transparent. This shows the photoproducts to be amorphous, in agreement with the observations in powder XRD pattern measurements [123].
Molecules 16 00119 g009 550
Figure 9. Polarizing optical micrographs of cocrystal 3/33 (a) before and after irradiation for (b) 15, (c) 30, (d) 60, (e) 120, (f) 180, (g) 240, and (h) 300 min.
Figure 9. Polarizing optical micrographs of cocrystal 3/33 (a) before and after irradiation for (b) 15, (c) 30, (d) 60, (e) 120, (f) 180, (g) 240, and (h) 300 min.
Molecules 16 00119 g009
The noncovalent interaction between two C6F5 rings was also used to steer stacking arrangements [126] and to induce [2+2] photocycloaddition [127] of olefin crystals. Irradiation of 33 gave dimer 36, formed by the reaction at the terminal double bonds of trienes, and a small amount of higher oligomers (Scheme 14) [123]. The offset for the stacking molecules in 33 was larger than those in 32 and 3/33. This results from weak C6F5···C6F5 intermolecular interactions relative to C6F5···C6H5interactions [128]. For the reacting two molecules of 33 in the stack, the distance between the terminal triene carbons was 5.939 Å, considerably larger than the (normal) upper limit of 4.2 Å for the [2+2] reaction. Consistent with its photoreactivity, even from this crystal excimer fluorescence was observed with monomer emission, indicating the presence of a significant degree of intermolecular π-orbital interactions in the excited state [122].
Molecules 16 00119 g026 550
Scheme 14. [2+2] Photodimerization and photopolymerization of 33.
Scheme 14. [2+2] Photodimerization and photopolymerization of 33.
Molecules 16 00119 g026
Also, trifluoromethyl groups have been proven to be effective to steer a parallel, offset stacked orientation suitable for [2+2] cycloaddition of aromatic olefins [129,130,131].
Trifluoromethyl-substituted (E,E)-DPB 37 was irradiated to afford dimer 38 in the solid state (Scheme 15) [129]. In the crystal structure of 37, the distance between the layers of molecule was 3.50 Å. UV-irradiation in solution resulted in the conversion of 37 to its Z-E isomer in >95% yield.
Molecules 16 00119 g027 550
Scheme 15. [2+2] Photodimerization of 37.
Scheme 15. [2+2] Photodimerization of 37.
Molecules 16 00119 g027
For (E,E)-1,4-bis[2,4-di(trifluoromethyl)phenyl]-1,3-butadiene, noncovalent π-π stacking interaction is considered to be mainly responsible for the observed offset stacked orientation [130]. In the crystal structure, olefins of neighboring layers were separated by 3.55 Å. UV-irradiation of the diene crystal for 15 h at room temperature yielded a [2+2] dimer as a single product in 80 % yield.

2.6. Substitution with Electron-Donating Groups

As described above, ring-substitution of (E,E,E)-DPH with electron-withdrawing cyano, formyl groups, or fluorine atoms induced solid-state [2+2] photocycloaddition at the triene double bonds. Up to now, however, no examples have been found for the photoreactive DPHs having electron-donating substituents. Thus, 4,4'-bis(N,N-dimethylamino)-substituted (E,E,E)-DPH and 4,4'-dimethoxy-substituted (E,E,E)-DPH were photostable in the solid state [45].
Although the single-crystal X-ray structure analysis of 4,4'-dimethoxy DPH has been unsuccessful at present, the two-dimensional 1H spin-exchange NMR spectrum showed that the methoxy group was located close to the triene chain of an adjacent molecule in the solid state [132]. This suggests that the molecular planes are stacked with a large offset along the long molecular axis. Therefore, the photostability of the 4,4'-dimethoxy derivative may at least partially be due to molecular alignment unfavorable for the [2+2] reaction. Further, since H atoms of the methoxy group are 'out-of-plane' atoms, this may possibly lead to the interplanar distance larger than 4 Å [63].

3. Atomic and Molecular Movements in Crystals during [2+2] Photodimerization and Photopolymerization

According to Schmidt's rule, the distances between the potentially reactive double bonds for topochemical [2+2] photocycloaddition should be less than ca. 4.2 Å [1,2,25]. However, several or more exceptions have been reported to this rule up to now [7,9]. Among the DPH derivatives described above, for example, 9, 20 and 24 were unreactive, although the double bond distances were shorter than 4.2 Å in the crystal structures. On the other hand, 33 was reactive, although the double bond distance of 5.939 Å was much longer than the criterion of 4.2 Å (Table 1).
Table
Table 1. Double bond distance and [2+2] photoreactivity for (E,E,E)-DPH crystals.
Table 1. Double bond distance and [2+2] photoreactivity for (E,E,E)-DPH crystals.
CrystalDouble bond distance a (Å)[2+2] Photoreactivity
37.730no
43.928yes
73.926yes
93.871no
203.862no
243.950no
324.067, 4.119yes
3/334.098, 4.126yes
335.939yes
a distance between the terminal triene carbons for the nearest stacking molecules.
For [2+2] cycloaddition to occur, atomic and molecular movements required by the formation of cyclobutane ring should be possible. When the interactions between the adjacent molecules are too strong, the movements will become difficult or almost impossible [133,134,135]. In this context, we can say that intermolecular interactions, used for constructing the stacking structure favorable for the [2+2] reaction, should be rather weak than too strong for the reaction to occur. Coumarin-3-carboxylic acid, for example, was photoreactive whereas 5-bromouracil and maleic acid were photostable, although the double bond distances were less than 4.2 Å in all three molecules [134]. The photostability of5-bromouracil and maleic acid was attributed to the presence of a much more extensive hydrogen bonding network in these two structures than in coumarin-3-carboxylic acid. Also for 1,3-phenylene-diacrylic acid, only the olefinic bonds adjacent to carboxylic groups involved in dimeric hydrogen bonds were photoreactive, while those associated with polymeric hydrogen bonds were photochemically inert [135].
Further, an enough space for the atomic and molecular movements in the crystal lattice is required by the reaction. For the [2+2] photodimerization of cinnamates 39 and 40 (Figure 10) in monolayers at the liquid/graphite interface, neither of the two molecules exhibited monomer packing ideal for the [2+2] reaction [136]. The double bonds were both separated by the distances larger than 4.2 Å. However, molecules 39 in monolayer, having a less closely packed adlayer structure, were photodimerizable. The photoreactivity was explained by means of packing fluctuations, allowing the reactive centers approach each other. While molecules 40, having an interdigitated structure, were resistant to photodimerization. In addition to the increased intermolecular distance, the interdigitation of the monomer molecules limited packing fluctuations. These were clearly evidenced by direct observation of the photoreaction using STM. The importance of a free space for molecular movements (conformational change) in the crystal lattice has also been pointed out for the photodimerization of two kinds of bulky olefins with 1,4-dihydropyridine skeleton [137].
Molecules 16 00119 g010 550
Figure 10. Chemical structures of cinnamates 39 and 40.
Figure 10. Chemical structures of cinnamates 39 and 40.
Molecules 16 00119 g010
Since [2+2] cycloaddition is a photoreaction of olefins, it requires sufficient interaction between π-orbitals of double bonds of the reacting two (or more) molecules, at least one of which is in the electronic excited state. Therefore, even if the double bond distance between the ground-state molecules determined by X-ray structure analysis is shorter than 4.2 Å, the reaction will not occur when the π-orbital interaction in the excited state is insufficient [133,138,139,140,141]. On the contrary, even if the double bond distance in the crystal structure is somewhat longer than 4.2 Å, the reaction can take place when the orbital interaction is enough [72,141,142]. Thus, the magnitude of orbital-orbital interaction in the excited state should be more important than the X-ray distance between double bonds in determining the [2+2] photoreactivity.
On the other hand, there are a few examples of [2+2] photoreactive olefin crystals in which double bond distances are much larger than 4.2 Å. Crystal 33 is one of such examples as described above. For [2+2] photodimerization in a self-assembled monolayer of 4-amyloxy CA on Au (111), direct observation using STM showed that the atoms and molecules moved in the structure during the photoreaction [143]. The molecular distance in the original monolayer was 6.0 Å. In this case, it is considered that photoexcitation creates short-term lattice instability [71,144,145,146], which drives one molecule close to a neighbor and gives the molecule a more favorable orientation so as to cause a photoreaction [143]. In the excited state, molecules are expected to be more attractive each other than in the ground state. Also for the [2+2] dimerization of 2-benzyl-5-benzilidenecyclopentanone derivatives, monitoring structural transformations in crystals using single-crystal XRD revealed that the reactant molecules were moving and even approaching each other during the photoreaction [147,148,149]. Such large molecular movements during the solid-state [2+2] reactions of olefins have also been suggested by other experimental observations [150,151,152].

4. Industrial Applications

4.1. Amorphous Materials

For amorphous molecular materials, very disordered structures are usually required [153,154]. [2+2] Photocycloaddition of olefins will easily give highly disordered and bulky structures. As in a molecule having a tetrahedral carbon framework [153], various functional groups can be attached as four arms to the cyclobutane ring carbons, leading to the formation of 'functional amorphous materials' (Figure 11).
Molecules 16 00119 g011 550
Figure 11. Four functional groups in (a) tetrahedral and (b)cyclobutane molecules.
Figure 11. Four functional groups in (a) tetrahedral and (b)cyclobutane molecules.
Molecules 16 00119 g011
The [2+2] photoproducts from crystals 32 and 3/33 were amorphous as shown above [123]. The [2+2] reaction of 1,3-phenylenediacrylic acid dimethyl ester [155,156] and α,α'-dicyano-1,4-phenylenediacrylic acid dimethyl ester [157] also gave amorphous oligomers.

4.2. Photocrosslinking Materials

Poly(vinyl cinnamate) 41 would be one of the most important photosensitive polymers. UV-light irradiation of the polymer gives a material with reduced solubility, which is considered to be due to photocrosslinking between cinnamoyl pendant groups in different polymer chains. The mechanism of photocrosslinking is proposed to be [2+2] cycloaddition of the olefinic groups (Scheme 16) [158,159,160,161,162,163,164].
Molecules 16 00119 g028 550
Scheme 16. Photocrosslinking reaction of poly(vinyl cinnamate) 41.
Scheme 16. Photocrosslinking reaction of poly(vinyl cinnamate) 41.
Molecules 16 00119 g028
Amorphous azo monomer 42 (Figure 12) having four cinnamate arms underwent [2+2] cycloaddition upon UV-light irradiation [165]. The monomer readily formed surface relief structures upon Ar+ laser irradiation, and the resulting structures were further stabilized through a photocrosslinking reaction induced by UV-light irradiation. On the basis of the material, two-dimensional quasi-crystal structures with different rotation symmetries were fabricated by using the dual-beam multiple exposure technique. The quasi-crystal structures were prepared simply through multistep light irradiation, and no subsequent wet-etch or dry-etch step was required in the process.
Molecules 16 00119 g012 550
Figure 12. Chemical structure of azo monomer 42.
Figure 12. Chemical structure of azo monomer 42.
Molecules 16 00119 g012

4.3. Photochemical Crack Healing in Polymeric Materials

[2+2] Photocycloaddition of cinnamoyl groups can be used as a crack healing reaction in polymeric materials [166]. A photocrosslinkable cinnamate monomer, 1,1,1-tris(cinnamoyloxymethyl)ethane, was irradiated with UV-light (λ > 280 nm) to give a transparent, insoluble film by crosslinking via the [2+2] reaction. It was expected that cyclobutane would reverse to original cinnamoyl structure upon crack formation and propagation, and the crack healing could be accomplished by the re-cycloaddition of cinnamoyl groups (Scheme 17). The photochemical healing proceeded very fast and did not require any catalyst, additive or severe heat-treatment.
Molecules 16 00119 g029 550
Scheme 17. Photochemical crack healing via [2+2] cycloaddition.
Scheme 17. Photochemical crack healing via [2+2] cycloaddition.
Molecules 16 00119 g029

4.4. Optical Memories and Fluorescence Switches

In the [2+2] photocycloaddition of highly conjugated molecules, the delocalized π-electron systems of olefin monomers are broken by the formation of aliphatic cyclobutane rings of dimeric or polymeric products. The solid-state fluorescence spectra, in general, dramatically change before and after the photoreaction, as the examples are shown above for 32 and 3/33 (Figure 8). Therefore, if the [2+2] reactions are photochemically reversible, they can be used for optical memories and fluorescence switches.
For tetra(2-benzoxazolyl)cyclobutane 43, the four benzoxazoles were electronically isolated and exhibited no fluorescence emission [167]. On irradiation with UV-light (λ = 254 nm), 43 cleaved to 1,2-di(2-benzoxazolyl)ethene 44, which showed strong emission at 420 nm. The reverse reaction occurred on UV-light (λ > 300 nm) irradiation (Scheme 18). Thus, 43 and 44 show typically optical bistability as a fluorescent switch, which can be applied in thermally stable, rewritable optical data storage. Most importantly, the fluorescence emission properties of conjugated molecules are able to be controlled only by irradiation of light.
Molecules 16 00119 g030 550
Scheme 18. Photocleavage of 43 and re-cycloaddition of 44.
Scheme 18. Photocleavage of 43 and re-cycloaddition of 44.
Molecules 16 00119 g030
In contrast, the crystal of cyano-stilbene derivative having trifluoromethyl substituents 45 was nonfluorescent due to the formation of π-dimer system but switched to highly fluorescent 46 when an external shear-strain and/or prolonged UV-light (λ = 365 nm) irradiation was applied (Scheme 19) [168]. The fluorescence modulation is due to the external and/or internal shear-induced lateral displacement of the π-dimer molecular pair. The fluorescence emission occurred at the cost of frustrated [2+2] cycloaddition. In this case the reverse reaction from 46 took place thermally. Thus the system provides an example of reversible fluorescence switching in the solid state.
Molecules 16 00119 g031 550
Scheme 19. [2+2] Photocycloaddition of 45 and the reverse reaction from 46.
Scheme 19. [2+2] Photocycloaddition of 45 and the reverse reaction from 46.
Molecules 16 00119 g031

5. Conclusions

Although having multiple reactive double bonds, the unsubstituted α,ω-diphenylpolyenes, (E,E)-DPB and (E,E,E)-DPH, underwent no [2+2] photocycloaddition in the solid state due to the unfavorable crystal packing for the reaction. However, with appropriate ring-substituents, noncovalent intermolecular interactions in crystals were effectively utilized to prealign molecules in stacking arrangements, suitable for the [2+2] photodimerization and photopolymerization.
Cyano- and formyl-substituted DPHs, 4 and 7 respectively, underwent solid-state [2+2] cycloaddition to give dimers and higher oligomers. The crystal structures were constructed by relatively weak intermolecular interactions such as CH···N and CH···O hydrogen bonds. It seems to be important that the interactions in the [2+2] photoreactive crystals should be rather weak than too strong, so as to make atomic and molecular movements required by the reaction easy in the crystal lattice.
The [2+2] photoreaction of perfluorinated DPHs 32 and 3/33 occurred more efficiently than those of 4 and 7 to afford dimers, trimers, and higher oligomers in moderate to reasonably good yields. The novel structures of the photoproducts were almost inaccessible by other synthetic methods. However, MWs of the polymeric products were relatively low. To improve this point, the positions of reactant molecules in crystals should not change largely during the photoreaction. For this purpose, it would be desirable to perform the reaction in a single-crystal-to-single-crystal manner, by controlling the light energy of irradiation (irradiation at the long wavelength tail of the absorption) [27,169,170] or by nanocrystallization of the reactants [171,172].
Interestingly, symmetrically perfluorinated DPH 33 was [2+2] photoreactive, despite the large distance of double bonds (5.939 Å) in the crystal. The result suggests that molecules can move and approach each other in the lattice on photoexcitation.
The chloro and donor-acceptor substituents were useful as steering groups for the [2+2] reactions of (E)-CA, and those of shorter α,ω-diphenylpolyenes such as (E)-stilbene and (E,E)-DPB. However, the substitution was ineffective to induce the reactions of (E,E,E)-DPHs. Despite the π-stacked molecular arrangements with double bond distances less than 4.2 Å, crystals 9, 20 and 24 were photostable. Although the reasons are unclear at present, the results suggest that the magnitude of π-orbital interactions in the excited state is more important in determining the [2+2] photoreactivity than the X-ray double bond distance in the ground state. This is consistent with the fact that the observation of solid-state excimer/monomer fluorescence correlates very well with [2+2] photoreactivity/unreactivity for all the DPH crystals examined.
The solid-state [2+2] photocycloaddition is one of the most useful photochemical reactions, not only in synthetic organic chemistry but also in material chemistry and applied physics. Only by light irradiation, very large changes in molecular structure are induced, which should consequently lead to large changes in electronic and optical properties of the molecules. Thus, if photochemical and/or thermal reverse reactions are available, the [2+2] reactions will find a wide variety of industrial applications.

Acknowledgements

The author thanks M Goto (AIST) for valuable discussions on the crystal structures of (E,E,E)-DPHs. Thanks are also due to H Akiyama (AIST) for his technical assistance with the polarizing optical microscopy experiments of cocrystal 3/33.

References and Notes

  1. Schmidt, G.M.J. Photodimerization in the solid state. Pure Appl. Chem. 1971, 27, 647–678. [Google Scholar] [CrossRef]
  2. Cohen, M.D. The photochemistry of organic solids. Angew. Chem. Int. Ed. Engl. 1975, 14, 386–393. [Google Scholar] [CrossRef]
  3. Green, B.S.; Lahav, M.; Rabinovich, D. Asymmetric synthesis via reactions in chiral crystals. Acc. Chem. Res. 1979, 12, 191–197. [Google Scholar] [CrossRef]
  4. Gavezzotti, A.; Simonetta, M. Crystal chemistry in organic solids. Chem. Rev. 1982, 82, 1–13. [Google Scholar] [CrossRef]
  5. Ramamurthy, V. Organic photochemistry in organized media. Tetrahedron 1986, 42, 5753–5839. [Google Scholar] [CrossRef]
  6. Ramamurthy, V.; Venkatesan, K. Photochemical reactions of organic crystals. Chem. Rev. 1987, 87, 433–481. [Google Scholar] [CrossRef]
  7. Murthy, G.S.; Arjunan, P.; Venkatesan, K.; Ramamurthy, V. Consequences of lattice relaxability in solid state photodimerizations. Tetrahedron 1987, 43, 1225–1240. [Google Scholar] [CrossRef]
  8. Ohashi, Y. Dynamical structure analysis of crystalline-state racemization. Acc. Chem. Res. 1988, 21, 268–274. [Google Scholar] [CrossRef]
  9. Photochemistry in Organized and Constrained Media; Ramamurthy, V. (Ed.) VCH: New York, NY, USA, 1991.
  10. Koshima, H.; Matsuura, T. Solid state photoreactions occurring at the interface between crystallites of two different organic compounds. J. Photochem. Photobiol. A Chem. 1996, 100, 85–91. [Google Scholar] [CrossRef]
  11. Ito, Y. Solid-state photoreactions in two-component crystals. Synthesis 1998, 1, 1–32. [Google Scholar] [CrossRef]
  12. Sonoda, Y. [2+2]-Photocycloadditions in the solid state. In CRC Handbook of Organic Photochemistry and Photobiology, 2nd; Horspool, W., Lenci, F., Eds.; CRC Press: Boca Raton, FL, USA, 2004; Chapter 73. [Google Scholar]
  13. Friščić, T.; MacGillivray, L.R. Single-crystal-to-single-crystal [2+2] photodimerizations: From discovery to design. Z. Kristallogr. 2005, 220, 351–363. [Google Scholar] [CrossRef]
  14. Toda, F. Solid state organic chemistry: Efficient reactions, remarkable yields, and stereoselectivity. Acc. Chem. Res. 1995, 28, 480–486. [Google Scholar] [CrossRef]
  15. Tanaka, K.; Toda, F. Solvent-free organic synthesis. Chem. Rev. 2000, 100, 1025–1074. [Google Scholar] [CrossRef]
  16. Toda, F. Thermal and photochemical reactions in the solid state. Top. Curr. Chem. 2005, 254, 1–40. [Google Scholar]
  17. Kaupp, G. Waste-free synthesis and production all across chemistry with the benefit of self-assembled crystal packings. J. Phys. Org. Chem. 2008, 21, 630–643. [Google Scholar] [CrossRef]
  18. Maekawa, Y.; Lim, P.-J.; Saigo, K.; Hasegawa, M. Preparation of a crystalline linear high copolymer by topochemical photopolymerization of diolefin mixed crystals. Macromolecules 1991, 24, 5752–5755. [Google Scholar] [CrossRef]
  19. Braga, D.; Grepioni, F. Reactions between or within molecular crystals. Angew. Chem. Int. Ed. 2004, 43, 4002–4011. [Google Scholar] [CrossRef]
  20. Avendaño, C.; Briceño, A. Concomitant [2+2] cycloaddition solid state reactions from co-crystals self-assembled via mechanochemistry. CrystEngCommunity 2009, 11, 408–411. [Google Scholar] [CrossRef]
  21. Nagarathinam, M.; Vittal, J.J. Solid-state synthesis of coordination polymers for [2+2] photoreactions by grinding. Aust. J. Chem. 2010, 63, 589–595. [Google Scholar] [CrossRef]
  22. Peedikakkal, A.M.P.; Vittal, J.J. Solid-state photochemical behavior of a triple-stranded ladder coordination polymer. Inorg. Chem. 2010, 49, 10–12. [Google Scholar]
  23. Cohen, M.D.; Schmidt, G.M.J. Topochemistry. Part I. A survey. J. Chem. Soc. 1964, 1996–2000. [Google Scholar]
  24. Cohen, M.D.; Schmidt, G.M.J.; Sonntag, F.I. Topochemistry. Part II. The photochemistry of trans-cinnamic acids. J. Chem. Soc. 1964, 2000–2013. [Google Scholar]
  25. Schmidt, G.M.J. Topochemistry. Part III. The crystal chemistry of some trans-cinnamic acids. J. Chem. Soc. 1964, 2014–2021. [Google Scholar] [CrossRef]
  26. Quina, F.H.; Whitten, D.G. Photochemical reactions in organized monolayer assemblies. 4. Photodimerization, photoisomerization, and excimer formation with surfactant olefins and dienes in monolayer assemblies, crystals, and micelles. J. Am. Chem. Soc. 1977, 99, 877–883. [Google Scholar] [CrossRef]
  27. Novak, K.; Enkelmann, V.; Wegner, G.; Wagener, K.B. Crystallographic study of a single crystal to single crystal photodimerization and its thermal reverse reaction. Angew. Chem. Int. Ed. Engl. 1993, 32, 1614–1616. [Google Scholar] [CrossRef]
  28. Kole, G.K.; Tan, G.K.; Vittal, J.J. Anion-controlled stereoselective synthesis of cyclobutane derivatives by solid-state [2+2] cycloaddition reaction of the salts of trans-3-(4-pyridyl) acrylic acid. Org. Lett. 2010, 12, 128–131. [Google Scholar] [CrossRef]
  29. Vedernikov, A.I.; Kuz´mina, L.G.; Sazonov, S.K.; Lobova, N.A.; Loginov, P.S.; Churakov, A.V.; Strelenko, Y.A.; Howard, J.A.K.; Alfimov, M.V.; Gromov, S.P. Styryl dyes. Synthesis and study of the solid-state [2+2] autophotocycloaddition by NMR spectroscopy and X-ray diffraction. Russ. Chem. Bull. Int. Ed. 2007, 56, 1860–1883. [Google Scholar] [CrossRef]
  30. Kuz’mina, L.G.; Vedernikov, A.I.; Sazonov, S.K.; Lobova, N.A.; Loginov, P.S.; Howard, J.A.K.; Alfimov, M.V.; Gromov, S.P. Specific features of the crystal packing that enable styryl dyes of the pyridine series to undergo the solid-phase [2+2] photocycloaddition including the process with single crystal retention. Crystallogr. Rep. 2008, 53, 428–450. [Google Scholar] [CrossRef]
  31. Tulyakova, E.V.; Fedorova, O.A.; Fedorov, Y.V.; Anisimov, A.V. [2+2]-Photocycloaddition reaction of self-assembled crown-containing 2-styrylpyridinium perchlorate in a solid state. J. Photochem. Photobiol. A Chem. 2008, 200, 90–95. [Google Scholar] [CrossRef]
  32. Kuz´mina, L.G.; Vedernikov, A.I.; Lobova, N.A.; Sazonov, S.K.; Basok, S.S.; Howard, J.A.K.; Gromov, S.P. Design of crystal packings of styrylheterocycles and [2+2] photocycloaddition reactions in their single crystals 6. Synthesis and crystal packings of neutral crown-containing and model styrylheterocycles. Russ. Chem. Bull. Int. Ed. 2009, 58, 1192–1210. [Google Scholar] [CrossRef]
  33. Friščić, T.; MacGillivray, L.R. Cyclophanes and ladderanes: Molecular targets for supramolecular chemists. Supramol. Chem. 2005, 17, 47–51. [Google Scholar]
  34. MacGillivray, L.R.; Papaefstathiou, G.S.; Friščić, T.; Hamilton, T.D.; Bučar, D.-K.; Chu, Q.; Varshney, D.B.; Georgiev, I.G. Supramolecular control of reactivity in the solid state: From templates to ladderanes to metal-organic frameworks. Acc. Chem. Res. 2008, 41, 280–291. [Google Scholar] [CrossRef]
  35. MacGillivray, L.R. Organic synthesis in the solid state via hydrogen-bond-driven self-assembly. J. Org. Chem. 2008, 73, 3311–3317. [Google Scholar] [CrossRef]
  36. Nagarathinam, M.; Vittal, J.J. A rational approach to crosslinking of coordination polymers using the photochemical [2+2] cycloaddition reaction. Macromol. Rapid Commun. 2006, 27, 1091–1099. [Google Scholar] [CrossRef]
  37. Nagarathinam, M.; Peedikakkal, A.M.P.; Vittal, J.J. Stacking of double bonds for photochemical [2+2] cycloaddition reactions in the solid state. Chem. Commun. 2008, 5277–5288. [Google Scholar]
  38. Han, Y.-F.; Lin, Y.-J.; Jia, W.-G.; Wang, G.-L.; Jin, G.-X. Template-controlled topochemical photodimerization based on ''organometallic macrocycles'' through single-crystal to single-crystal transformation. Chem. Commun. 2008, 1807–1809. [Google Scholar]
  39. Han, Y.-F.; Jia, W.-G.; Yu, W.-B.; Jin, G.-X. Stepwise formation of organometallic macrocycles, prisms and boxes from Ir, Rh and Ru-based half-sandwich units. Chem. Soc. Rev. 2009, 38, 3419–3434. [Google Scholar] [CrossRef]
  40. Zhang, W.-Z.; Han, Y.-F.; Lin, Y.-J.; Jin, G.-X. [2+2] Photodimerization in the solid state aided by molecular templates of rectangular macrocycles bearing oxamidato ligands. Organometallics 2010, 29, 2842–2849. [Google Scholar] [CrossRef]
  41. Hasegawa, M. Photopolymerization of diolefin crystals. Chem. Rev. 1983, 83, 507–518. [Google Scholar] [CrossRef]
  42. Hasegawa, M. Photodimerization and photopolymerization of diolefin crystals. Adv. Phys. Org. Chem. 1995, 30, 117–171. [Google Scholar] [CrossRef]
  43. Cohen, M.D.; Elgavi, A.; Green, B.S.; Ludmer, Z.; Schmidt, G.M.J. Photodimerization and excimer emission in a crystalline 1,4-diphenylbutadiene. J. Am. Chem. Soc. 1972, 94, 6776–6779. [Google Scholar] [CrossRef]
  44. Singh, A.K.; Krishna, T.S.R. Fluorescence and photodimerization studies of cyano-substituted diphenylbutadienes. J. Phys. Chem. A 1997, 101, 3066–3069. [Google Scholar] [CrossRef]
  45. Sonoda, Y.; Miyazawa, A.; Hayashi, S.; Sakuragi, M. Intermolecular [2+2] photocycloaddition of formyl- and cyano-substituted diphenylhexatrienes in the solid state. Chem. Lett. 2001, 30, 410–411. [Google Scholar]
  46. Drenth, W.; Wiebenga, E.H. Structure of α,ω-diphenylpolyenes. 1. Crystal data of 1,4-diphenyl-1,3-butadiene, 1,6-diphenyl-1,3,5-hexatriene and 1,8-diphenyl-1,3,5,7-octatetraene. Recl. Trav. Chim. Pays-Bas 1953, 72, 39–43. [Google Scholar]
  47. Glaser, R.; Dendi, L.R.; Knotts, N.; Barnes, C.L. Ab initio and crystal structures of (E,E)-1,4-diphenylbutadiene: A new type ofarene-arene double T-contact and an interesting interlayer cooperation involving diastereoisomeric contacts. Cryst. Growth Des. 2003, 3, 291–300. [Google Scholar] [CrossRef]
  48. Gavezzotti, A.; Desiraju, G.R. A systematic analysis of packing energies and other packing parameters for fused-ring aromatic hydrocarbons. Acta Crystallogr. 1988, B44, 427–434. [Google Scholar]
  49. Desiraju, G.R.; Gavezzotti, A. Crystal structures of polynuclear aromatic hydrocarbons. Classification, rationalization and prediction from molecular structure. Acta Crystallogr. 1989, B45, 473–482. [Google Scholar]
  50. Hall, T.; Bachrach, S.M.; Spangler, C.W.; Sapochak, L.S.; Lin, C.T.; Guan, H.W.; Rogers, R.D. Structure of all-trans-1,6-diphenyl- (A) and all-trans-1,6-bis(o-methoxyphenyl)-1,3,5-hexatriene (B). Acta Crystallogr. 1989, C45, 1541–1543. [Google Scholar]
  51. Sonoda, Y.; Morii, H.; Sakuragi, M.; Suzuki, Y. Substituent effect on the cis-trans photoisomerization of trans,trans,trans-1,6-diphenyl-1,3,5-hexatrienes. Chem. Lett. 1998, 27, 349–350. [Google Scholar]
  52. Sonoda, Y.; Kwok, W.M.; Petrasek, Z.; Ostler, R.; Matousek, P.; Towrie, M.; Parker, A.W.; Phillips, D. Solvent effects on the photophysical and photochemical properties of (E,E,E)-1,6-bis(4-nitrophenyl)hexa-1,3,5-triene. J. Chem. Soc. Perkin Trans. 2 2001, 308–314. [Google Scholar]
  53. The crystal structures of 4 and 7 are to be published elsewhere
  54. Reddy, D.S.; Goud, B.S.; Panneerselvam, K.; Desiraju, G.R. C–H···N mediated hexagonal network in the crystal structure of the 1:1 molecular complex 1,3,5-tricyanobenzene-hexamethylbenzene. J. Chem. Soc. Chem. Commun. 1993, 663–664. [Google Scholar]
  55. Desiraju, G.R. Supramolecular synthons in crystal engineering—A new organic synthesis. Angew. Chem. Int. Ed. Engl. 1995, 34, 2311–2327. [Google Scholar] [CrossRef]
  56. Desiraju, G.R. Designer crystals: Intermolecular interactions, network structures and supramolecular synthons. Chem. Commun. 1997, 1475–1482. [Google Scholar] [CrossRef]
  57. Nangia, A.; Desiraju, G.R. Supramolecular structures - reason and imagination. Acta Crystallogr. 1998, A54, 934–944. [Google Scholar]
  58. Dhurjati, M.S.K.; Sarma, J.A.R.P.; Desiraju, G.R. Unusual [2+2] topochemical cycloadditions of 3-cyano- and 4-cyano-cinnamic acids: Temperature dependent solid state photochemical reactions. J. Chem. Soc. Chem. Commun. 1991, 1702–1703. [Google Scholar]
  59. Sonoda, Y.; Kawanishi, Y.; Ikeda, T.; Goto, M.; Hayashi, S.; Yoshida, Y.; Tanigaki, N.; Yase, K. Fluorescence spectra for the microcrystals and thin films of trans,trans,trans-1,6-diphenyl-1,3,5-hexatrienes. J. Phys. Chem. B 2003, 107, 3376–3383. [Google Scholar]
  60. Sonoda, Y.; Suzuki, Y. Stereoselective Z,E-photoisomerization of formyl-substituted (E,E,E)-1,6-diphenylhexa-1,3,5-triene in solution. J. Chem. Soc. Perkin Trans. 2 1996, 401–404. [Google Scholar] [CrossRef]
  61. Sonoda, Y.; Suzuki, Y. Solvent-dependent cis-trans one-way photoisomerization of bisformyl-substituted 1,6-diphenyl-1,3,5-hexatriene. Chem. Lett. 1996, 25, 659–660. [Google Scholar] [CrossRef]
  62. Sonoda, Y.; Kawanishi, Y.; Sakuragi, M. A heavy-atom effect on the cis-trans photoisomerization of bisforlmyl-substituted trans,trans,trans-1,6-diphenyl-1,3,5-hexatriene. Chem. Lett. 1999, 28, 587–588. [Google Scholar]
  63. Sarma, J.A.R.P.; Desiraju, G.R. The role of Cl···Cl and C–H···O interactions in the crystal engineering of 4-A short-axis structures. Acc. Chem. Res. 1986, 19, 222–228. [Google Scholar] [CrossRef]
  64. Desiraju, G.R. The C–H···O hydrogen bond in crystals: What is it? Acc. Chem. Res. 1991, 24, 290–296. [Google Scholar] [CrossRef]
  65. Desiraju, G.R. The C–H···O hydrogen bond: Structural implications and supramolecular design. Acc. Chem. Res. 1996, 29, 441–449. [Google Scholar] [CrossRef]
  66. Steiner, T.; Desiraju, G.R. Distinction between the weak hydrogen bond and the van der Waals interaction. Chem. Commun. 1998, 891–892. [Google Scholar] [CrossRef]
  67. Desiraju, G.R. Hydrogen bridges in crystal engineering: Interactions without borders. Acc. Chem. Res. 2002, 35, 565–573. [Google Scholar] [CrossRef]
  68. Desiraju, G.R. C–H···O and other weak hydrogen bonds. From crystal engineering to virtual screening. Chem. Commun. 2005, 2995–3001. [Google Scholar] [CrossRef]
  69. Nakanishi, F.; Nakanishi, H.; Tasai, T.; Suzuki, Y.; Hasegawa, M. Water participation in the crystalline state photoreaction photodimerization of p-formylcinnamic acid. Chem. Lett. 1974, 3, 525–528. [Google Scholar]
  70. Nakanishi, F.; Nakanishi, H.; Tsuchiya, M.; Hasegawa, M. Water-participation in the crystalline-state photodimerization of cinnamic acid derivatives. A new type of organic photoreaction. Bull. Chem. Soc. Jpn. 1976, 49, 3096–3099. [Google Scholar] [CrossRef]
  71. Ghosh, U.; Misra, T.N. Spectroscopic studies of photochemical reactions in organic solids. Photodimerization of p-formylcinnamic acid. Bull. Chem. Soc. Jpn. 1985, 58, 2403–2406. [Google Scholar] [CrossRef]
  72. Nakanishi, H.; Hasegawa, M.; Mori, T. Structure of the β-form of p-formylcinnamic acid, C10H8O3, a photodimerizable crysta. Acta Crystallogr. 1985, C41, 70–71. [Google Scholar]
  73. Sharma, C.V.K.; Desiraju, G.R. C–H···O hydrogen bond patterns in crystalline nitro compounds: Studies in solid-state molecular recognition. J. Chem. Soc. Perkin Trans. 2 1994, 2345–2352. [Google Scholar]
  74. Thaimattam, R.; Xue, F.; Sarma, J.A.R.P.; Mak, T.C.W.; Desiraju, G.R. Inclusion compounds of tetrakis(4-nitrophenyl)methane: C–H···O networks, pseudopolymorphism, and structural transformations. J. Am. Chem. Soc. 2001, 123, 4432–4445. [Google Scholar]
  75. Sonoda, Y.; Kawanishi, Y.; Goto, M. (E,E,E)-1,6-Bis(4-nitrophenyl)hexa-1,3,5-triene. Acta Crystallogr. 2005, E61, o1200–o1202. [Google Scholar]
  76. Sonoda, Y.; Tsuzuki, S.; Goto, M.; Tohnai, N.; Yoshida, M. Fluorescence spectroscopic properties of nitro-substituted diphenylpolyenes: Effects of intramolecular planarization and intermolecular interactions in crystals. J. Phys. Chem. A 2010, 114, 172–182. [Google Scholar]
  77. Desiraju, G.R.; Sharma, C.V.K.M. C–H···O hydrogen bonding and topochemistry in crystalline 3,5-dinitrocinnamic acid and its 1:1 donor–acceptor complex with 2,5-dimethoxycinnamic acid. J. Chem. Soc. Chem. Commun. 1991, 1239–1241. [Google Scholar]
  78. Sharma, C.V.K.; Panneerselvam, K.; Shimoni, L.; Katz, H.; Carrell, H.L.; Desiraju, G.R. 3-(3',5'-Dinitrophenyl)-4-(2',5'-dimethoxyphenyl)cyclobutane-1,2-dicarboxylic acid: Engineered topochemical synthesis and molecular and supramolecular properties. Chem. Mater. 1994, 6, 1282–1292. [Google Scholar] [CrossRef]
  79. Capparelli, M.V.; Codding, P.W. Photodimerization of α,ω-diarylbutadienes. I. Crystal and molecular structures of trans,trans-l-(2'-methoxyphenyl)-4-(4'-nitrophenyl)-l,3-butadiene and its photodimer. Can. J. Chem. 1993, 71, 942–950. [Google Scholar] [CrossRef]
  80. Mascitti, V.; Corey, E.J. Photochemical studies on ladderane formation from conjugated esters in solution or solid phase. Tetrahedron Lett. 2006, 47, 5879–5882. [Google Scholar] [CrossRef]
  81. Sonoda, Y.; Goto, M.; Tsuzuki, S.; Tamaoki, N. Fluorescence spectroscopic properties and crystal structure of a series of donor-acceptor diphenylpolyenes. J. Phys. Chem. A 2006, 110, 13379–13387. [Google Scholar] [CrossRef]
  82. Sonoda, Y.; Kawanishi, Y. Solvent-dependent cis-trans photoisomerization of p-methoxy-p′-nitro-substituted trans,trans,trans-1,6-diphenyl-1,3,5-hexatriene. Chem. Lett. 2003, 32, 978–979. [Google Scholar] [CrossRef]
  83. Sarma, J.A.R.P.; Desiraju, G.R. The chloro-substituent as a steering group: A comparative study of non-bonded interactions and hydrogen bonding in crystalline chloro-aromatics. Chem. Phys. Lett. 1985, 117, 160–164. [Google Scholar] [CrossRef]
  84. Desiraju, G.R.; Parthasarathy, R. The nature of halogen···halogen interactions: Are short halogen contacts due to specific attractive forces or due to close packing of nonspherical atoms? J. Am. Chem. Soc. 1989, 111, 8725–8726. [Google Scholar] [CrossRef]
  85. Pedireddi, V.R.; Reddy, D.S.; Goud, B.S.; Craig, D.C.; Rae, A.D.; Desiraju, G.R. The nature of halogen···halogen interactions and the crystal structure of 1,3,5,7-tetraiodoadamantane. J. Chem. Soc. Perkin Trans. 2 1994, 2353–2360. [Google Scholar]
  86. Reddy, C.M.; Kirchner, M.T.; Gundakaram, R.C.; Padmanabhan, K.A.; Desiraju, G.R. Isostructurality, polymorphism and mechanical properties of some hexahalogenated benzenes: The nature of halogen···halogen interactions. Chem. Eur. J. 2006, 12, 2222–2234. [Google Scholar] [CrossRef]
  87. Bui, T.T.T.; Dahaoui, S.; Lecomte, C.; Desiraju, G.R.; Espinosa, E. The nature ofhalogen···halogen interactions: A model derived from experimental charge-density analysis. Angew. Chem. Int. Ed. 2009, 48, 3838–3841. [Google Scholar]
  88. Sarma, J.A.R.P.; Desiraju, G.R. Crystal engineering via Cl···Cl non-bonded interactions. The novel 2:1 complex, 6-chloro-3,4-(methylenedioxy)cinnamic acid-2,4-dichlorocinnamic acid. Topochemical conversion into an unsymmetrical cyclobutane and kinetics of the reaction. J. Chem. Soc. Chem. Commun. 1984, 145–147. [Google Scholar]
  89. Cohen, M.D.; Green, B.S.; Ludmer, Z.; Schmidt, G.M.J. Excimer emission and photodimerization in a crystalline stilbene. Chem. Phys. Lett. 1970, 7, 486–490. [Google Scholar] [CrossRef]
  90. Cohen, R.; Ludmer, Z.; Yakhot, V. Structural influence on the excimer emission from a dimorphic crystalline stilbene. Chem. Phys. Lett. 1975, 34, 271–274. [Google Scholar] [CrossRef]
  91. Elgavi, A.; Green, B.S.; Schmidt, G.M.J. Reactions in chiral crystals. Optically active heterophotodimer formation from chiral single crystals. J. Am. Chem. Soc. 1973, 95, 2058–2059. [Google Scholar] [CrossRef]
  92. Green, B.S.; Heller, L. Solution and solid-state photodimerization of some styrylthiophenes. J. Org. Chem. 1974, 39, 196–201. [Google Scholar] [CrossRef]
  93. Warshel, A.; Shakked, Z. Theoretical study of excimers in crystals of flexible conjugated molecules. Excimer formation and photodimerization in crystalline 1,4-diphenylbutadiene. J. Am. Chem. Soc. 1975, 97, 5679–5684. [Google Scholar] [CrossRef]
  94. Sonoda, Y.; Kawanishi, Y.; Goto, M. (E,E,E)-1,6-Bis(2,4-di-chloro-phenyl)-hexa-1,3,5-triene. Acta Crystallogr. 2003, C59, o311–o313. [Google Scholar]
  95. Thalladi, V.R.; Weiss, H.-C.; Bläser, D.; Boese, R.; Nangia, A.; Desiraju, G.R. C–H···F interactions in the crystal structures of some fluorobenzenes. J. Am. Chem. Soc. 1998, 120, 8702–8710. [Google Scholar]
  96. Desiraju, G.R. Crystal engineering: A holistic view. Angew. Chem. Int. Ed. 2007, 46, 8342–8356. [Google Scholar] [CrossRef]
  97. Kumar, V.A.; Begum, N.S.; Venkatesan, K. Crystal engineering: Fluorine as a new steering group. J. Chem. Soc. Perkin Trans. 2 1993, 463–467. [Google Scholar]
  98. Vishnumurthy, K.; Guru Row, T.N.; Venkatesan, K. Studies in crystal engineering: Effect of fluorine substitution in crystal packing and topological photodimerization of styryl coumarins in the solid state. J. Chem. Soc. Perkin Trans. 2 1996, 1475–1478. [Google Scholar]
  99. Vishnumurthy, K.; Guru Row, T.N.; Venkatesan, K. Studies in crystal engineering: Crystal packing, topological photodimerization and structure–reactivity correlations in fluoro-substituted styrylcoumarins. J. Chem. Soc. Perkin Trans. 2 1997, 615–619. [Google Scholar]
  100. Vishnumurthy, K.; Guru Row, T.N.; Venkatesan, K. Unusual photodimerization of 7-fluoro-4-methylcoumarin and 6-fluoro-4-methylcoumarin in the solid state. Tetrahedron 1998, 54, 11235–11246. [Google Scholar] [CrossRef]
  101. Vishnumurthy, K.; Guru Row, T.N.; Venkatesan, K. Studies in crystal engineering: Steering ability of fluorine in 4-styrylcoumarins. Tetrahedron 1999, 55, 4095–4108. [Google Scholar] [CrossRef]
  102. Mori, Y.; Matsumoto, A. Photodimerization mechanism of bis(3,4,5-trifluorobenzyl) (E,E)-muconate in a columnar assembly in the crystalline state. Chem. Lett. 2007, 36, 510–511. [Google Scholar] [CrossRef]
  103. Mori, Y.; Matsumoto, A. Molecular stacking and photoreactions of fluorine-substituted benzyl muconates in the crystals. Cryst. Growth Des. 2007, 7, 377–385. [Google Scholar] [CrossRef]
  104. Cozzi, F.; Ponzini, F.; Annunziata, R.; Cinquini, M.; Siegel, J.S. Polar interactions between stacked π systems in fluorinated 1,8-diarylnaphthalenes: Importance of quadrupole moments in molecular recognition. Angew. Chem. Int. Ed. Engl. 1995, 34, 1019–1020. [Google Scholar] [CrossRef]
  105. Cozzi, F.; Siegel, J.S. Interaction between stacked aryl groups in 1,8-diarylnaphthalenes: Dominance of polar/π over charge-transfer effects. Pure Appl. Chem. 1995, 67, 683–689. [Google Scholar] [CrossRef]
  106. Adams, H.; Blanco, J.-L.J.; Chessari, G.; Hunter, C.A.; Low, C.M.R.; Sanderson, J.M.; Vinter, J.G. Quantitative determination of intermolecular interactions with fluorinated aromatic rings. Chem. Eur. J. 2001, 7, 3494–3503. [Google Scholar] [CrossRef]
  107. Gung, B.W.; Patel, M.; Xue, X. A threshold for charge transfer in aromatic interactions? A quantitative study of π-stacking interactions. J. Org. Chem. 2005, 70, 10532–10537. [Google Scholar] [CrossRef]
  108. Reichenbächer, K.; Süss, H.I.; Hulliger, J. Fluorine in crystal engineering—“the little atom that could”. Chem. Soc. Rev. 2005, 34, 22–30. [Google Scholar] [CrossRef]
  109. Gung, B.W.; Xue, X.; Zou, Y. Enthalpy (ΔH) and entropy (ΔS) for π-stacking interactions in near-sandwich configurations: Relative importance of electrostatic, dispersive, and charge-transfer effects. J. Org. Chem. 2007, 72, 2469–2475. [Google Scholar] [CrossRef]
  110. Brock, C.P.; Naae, D.G.; Goodhand, N.; Hamor, T.A. A statistical comparison of two determinations of the crystal structure of 2,3,4,5,6-pentafluorobiphenyl, a molecule forming mixed stacks in the solid state. Acta Crystallogr. 1978, B34, 3691–3696. [Google Scholar]
  111. Naae, D.G. Biphenyl–perfluorobiphenyl; 1:1 molecular complex. Acta Crystallogr. 1979, B35, 2765–2768. [Google Scholar]
  112. Bartholomew, G.P.; Bazan, G.C.; Bu, X.; Lachicotte, R.J. Packing modes of distyrylbenzene derivatives. Chem. Mater. 2000, 12, 1422–1430. [Google Scholar] [CrossRef]
  113. Bartholomew, G.P.; Bu, X.; Bazan, G.C. Preferential cocrystallization among distyrylbenzene derivatives. Chem. Mater. 2000, 12, 2311–2318. [Google Scholar] [CrossRef]
  114. Feast, W.J.; Lövenich, P.W.; Puschmann, H.; Taliani, C. Synthesis and structure of 4,4′-bis(2,3,4,5,6-pentafluorostyryl)stilbene, a self-assembling J aggregate based on aryl–fluoroaryl interactions. Chem. Commun. 2001, 505–506. [Google Scholar]
  115. Bunz, U.H.F.; Enkelmann, V. Structure elucidation, packing, and solid-state behavior of the eglinton - Galbraith dimer. Chem. Eur. J. 1999, 5, 263–266. [Google Scholar] [CrossRef]
  116. Nishinaga, T.; Nodera, N.; Miyata, Y.; Komatsu, K. Dehydro[12]- and -[18]annulenes fused with tetrafluorobenzene: Synthesis, electronic properties, packing structures, and reactivity in the solid state. J. Org. Chem. 2002, 67, 6091–6096. [Google Scholar] [CrossRef]
  117. Ponzini, F.; Zagha, R.; Hardcastle, K.; Siegel, J.S. Phenyl/pentafluorophenyl interactions and the generation of ordered mixed crystals: sym-Triphenethynylbenzene and sym-tris(perfluorophenethynyl)benzene. Angew. Chem. Int. Ed. 2000, 39, 2323–2325. [Google Scholar] [CrossRef]
  118. Watt, S.W.; Dai, C.; Scott, A.J.; Burke, J.M.; Thomas, R.L.; Collings, J.C.; Viney, C.; Clegg, W.; Marder, T.B. Structure and phase behavior of a 2:1 complex between arene- and fluoroarene-based conjugated rigid rods. Angew. Chem. Int. Ed. 2004, 43, 3061–3063. [Google Scholar]
  119. Smith, C.E.; Smith, P.S.; Thomas, R.L.; Robins, E.G.; Collings, J.C.; Dai, C.; Scott, A.J.; Borwick, S.; Batsanov, A.S.; Watt, S.W.; Clark, S.J.; Viney, C.; Howard, J.A.K.; Clegg, W.; Marder, T.B. Arene-perfluoroarene interactions in crystal engineering: Structural preferences in polyfluorinated tolans. J. Mater. Chem. 2004, 14, 413–420. [Google Scholar]
  120. Coates, G.W.; Dunn, A.R.; Henling, L.M.; Ziller, J.W.; Lobkovsky, E.B.; Grubbs, R.H. Phenyl-perfluorophenyl stacking interactions: Topochemical [2+2] photodimerization and photopolymerization of olefinic compounds. J. Am. Chem. Soc. 1998, 120, 3641–3649. [Google Scholar]
  121. Vishnumurthy, K.; Guru Row, T.N.; Venkatesan, K. Fluorine in crystal engineering: Photodimerization of (1E,3E)-1-phenyl-4-pentafluorophenylbuta-1,3-dienes in the crystalline state. Photochem. Photobiol. Sci. 2002, 1, 427–430. [Google Scholar] [CrossRef]
  122. Sonoda, Y.; Goto, M.; Tsuzuki, S.; Tamaoki, N. Fluorinated diphenylpolyenes:Crystal structures and emission properties. J. Phys. Chem. A 2007, 111, 13441–13451. [Google Scholar] [CrossRef]
  123. Sonoda, Y.; Goto, M.; Tsuzuki, S.; Akiyama, H.; Tamaoki, N. [2+2] Photodimerization and photopolymerization of diphenylhexatrienecrystals utilizing perfluorophenyl-phenyl stacking interactions. J. Fluorine Chem. 2009, 130, 151–157. [Google Scholar] [CrossRef]
  124. Coates, G.W.; Dunn, A.R.; Henling, L.M.; Dougherty, D.A.; Grubbs, R.H. Phenyl-perfluorophenyl stacking interactions: A new strategy for supermolecule construction. Angew. Chem. Int. Ed. Engl. 1997, 36, 248–251. [Google Scholar]
  125. Xu, R.; Gramlich, V.; Frauenrath, H. Alternating diacetylene copolymer utilizing perfluorophenyl-phenyl interactions. J. Am. Chem. Soc. 2006, 128, 5541–5547. [Google Scholar] [CrossRef]
  126. Liu, J.; Murray, E.M.; Young, V.G., Jr. π-Stacking interactions in some crystalline cisoid E,E-1,4-diaryl-1,3-butadienes. Chem. Commun. 2003, 1904–1905. [Google Scholar]
  127. Caronna, T.; Liantonio, R.; Logothetis, T.A.; Metrangolo, P.; Pilati, T.; Resnati, G. Halogen bonding and π···π stacking control reactivity in the solid state. J. Am. Chem. Soc. 2004, 126, 4500–4501. [Google Scholar] [CrossRef]
  128. Frontera, A.; Quiñonero, D.; Costa, A.; Ballester, P.; Deyà, P.M. MP2 study of cooperative effects between cation–π, anion–π and π–π interactions. New J. Chem. 2007, 31, 556–560. [Google Scholar] [CrossRef]
  129. Liu, J.; Boarman, K.J. Regiospecific topochemical reactions controlled by trifluoromethyl directing groups. Chem. Commun. 2005, 340–341. [Google Scholar]
  130. Liu, J.; Wendt, N.L.; Boarman, K.J. Trifluoromethyl groups in crystal design of 1,4-diphenyl-1,3-butadienes for topochemical [2 + 2] photodimerization. Org. Lett. 2005, 7, 1007–1010. [Google Scholar] [CrossRef]
  131. Jeannin, O.; Fourmigué, M. Fluorine segregation in crystalline materials: Structural control and solid-state [2+2] cycloaddition in CF3-substituted tetrathiafulvalene derivatives. Chem. Eur. J. 2006, 12, 2994–3005. [Google Scholar] [CrossRef]
  132. Hayashi, S. wo-dimensional 1H spin-exchange NMR study of molecular arrangements in diphenylhexatrienes. Bull. Chem. Soc. Jpn. 2004, 77, 2159–2164. [Google Scholar] [CrossRef]
  133. Turowska-Tyrk, I.; Grześniak, K.; Trzop, E.; Zych, T. Monitoring structural transformations in crystals. Part 4. Monitoring structural changes in crystals of pyridine analogs of chalcone during [2+2]-photodimerization and possibilities of the reaction in hydroxy derivatives. J. Solid State Chem. 2003, 174, 459–465. [Google Scholar] [CrossRef]
  134. Mahon, M.F.; Raithby, P.R.; Sparkes, H.A. nvestigation of the factors favouring solid state [2 + 2] cycloaddition reactions; the [2 + 2] cycloaddition reaction of coumarin-3-carboxylic acid. CrystEngCommunity 2008, 10, 573–576. [Google Scholar] [CrossRef]
  135. Yang, S.-Y.; Naumov, P.; Fukuzumi, S. Topochemical limits for solid-state photoreactivity by fine tuning of the π-π interactions. J. Am. Chem. Soc. 2009, 131, 7247–7249. [Google Scholar] [CrossRef]
  136. Abdel-Mottaleb, M.M.S.; De Feyter, S.; Gesquière, A.; Sieffert, M.; Klapper, M.; Müllen, K.; De Schryver, F.C. Photodimerization of cinnamate derivatives studied by STM. Nano Lett. 2001, 1, 353–359. [Google Scholar] [CrossRef]
  137. Marubayashi, N.; Ogawa, T.; Hamasaki, T.; Hirayama, N. A buffer zone in the crystal structure that governs the solid-state photodimerization of bulky olefins with the 1,4-dihydropyridine skeleton. J. Chem. Soc. Perkin Trans. 2 1997, 1309–1314. [Google Scholar]
  138. Gnanaguru, K.; Ramasubbu, N.; Venkatesan, K.; Ramamurthy, V. Topochemical solid state photodimerization of non-ideally oriented monomers: 7-Chlorocoumarin and 7-methoxy-coumarin. J. Photochem. 1984, 27, 355–362. [Google Scholar]
  139. Bhadbhade, M.M.; Murthy, G.S.; Venkatesan, K.; Ramamurthy, V. Topochemical dimerization of non-parallel double bonds: 7-Methoxycoumarin. Chem. Phys. Lett. 1984, 109, 259–263. [Google Scholar] [CrossRef]
  140. Gnanaguru, K.; Ramasubbu, N.; Venkatesan, K.; Ramamurthy, V. A Study on the photochemical dimerization of coumarins in the solid state. J. Org. Chem. 1985, 50, 2337–2346. [Google Scholar] [CrossRef]
  141. Liang, Y.-L.; Fang, J.-M.; Chow, T.; Ho, T.-I.; Lee, C.-R.; Wang, Y. Solution and solid-state photochemistry of 2-anilino-5-phenyl-2,4-pentadienenitriles. J. Org. Chem. 1994, 59, 5742–5747. [Google Scholar] [CrossRef]
  142. Fonseca, I.; Hayes, S.E.; Bertmer, M. Size effects of aromatic substitution in the ortho position on the photodimerization kinetics of α-trans cinnamic acid derivatives. A solid-state NMR study. Phys. Chem. Chem. Phys. 2009, 11, 10211–10218. [Google Scholar]
  143. Xu, L.-P.; Yan, C.-J.; Wan, L.-J.; Jiang, S.-G.; Liu, M.-H. Light-induced structural transformation in self-assembled monolayer of 4-(amyloxy)cinnamic acid investigated with scanning tunneling microscopy. J. Phys. Chem. B 2005, 109, 14773–14778. [Google Scholar] [CrossRef]
  144. Swiatkiewicz, J.; Eisenhardt, G.; Prasad, P.N.; Thomas, J.M.; Jones, W.; Theocharis, C.R. Phonon spectroscopy of photochemical reactions in organic solids: Photodimerization of 2-benzyl-5-benzylidenecyclopentanone and photopolymerization of 2,5-distyrylpyrazine. J. Phys. Chem. 1982, 86, 1764–1767. [Google Scholar] [CrossRef]
  145. Ghosh, M.; Mandal, T.K.; Chakrabarti, S.; Misra, T.N. Spectroscopic study of solid-state photoreaction in organic crystals: Photopolymerization of the dimethyl ester of p-phenylenediacrylic acid. J. Raman Spectrosc. 1998, 29, 807–811. [Google Scholar] [CrossRef]
  146. Eckhardt, C.J.; Luty, T.; Peachey, N.M. Collective interactions and solid state reactivity. Mol. Cryst. Liq. Cryst. 1998, 313, 25–38. [Google Scholar] [CrossRef]
  147. Turowska-Tyrk, I. Structural transformations in a crystal during the photochemical reaction of 2-benzyl-5-benzylidenecyclopentanone. Chem. Eur. J. 2001, 7, 3401–3405. [Google Scholar] [CrossRef]
  148. Turowska-Tyrk, I. Monitoring structural transformations in crystals. 5. A topotactic [2+2]-photodimerization reaction. Acta Crystallogr. 2003, B59, 670–675. [Google Scholar]
  149. Turowska-Tyrk, I. Structural transformations in organic crystals during photochemical reactions. J. Phys. Org. Chem. 2004, 17, 837–847. [Google Scholar] [CrossRef]
  150. Kim, J.H.; Matsuoka, M.; Fukunishi, K. Selective topochemical photoreaction of crystallized 2,3-bis(2-phenylethenyl)-4,5-dicyanopyrazines. Chem. Lett. 1999, 28, 143–144. [Google Scholar]
  151. Natarajan, A.; Mague, J.T.; Venkatesan, K.; Ramamurthy, V. Large molecular motions are tolerated in crystals of diamine double salt of trans-chlorocinnamic acids with trans-1,2-diaminocyclohexane. Org. Lett. 2005, 7, 1895–1898. [Google Scholar] [CrossRef]
  152. Zheng, S.-L.; Pham, O.; Vande Velde, C.M.L.; Gembicky, M.; Coppens, P. Competitive isomerization and dimerization in co-crystals of1,1,6,6-tetraphenyl-2,4-hexadiyne-1,6-diol and sorbic acid: A new look at stereochemical requirements for [2+2] dimerization. Chem. Commun. 2008, 2538–2540. [Google Scholar]
  153. Robinson, M.R.; Wang, S.; Heeger, A.J.; Bazan, G.C. A tetrahedral oligo(phenylenevinylene) molecule of intermediate dimensions: Effect of molecular shape on the morphology and electroluminescence of organic glasses. Adv. Func. Mater. 2001, 11, 413–419. [Google Scholar] [CrossRef]
  154. Shirota, Y. Photo- and electroactive amorphous molecular materials—molecular design, syntheses, reactions, properties, and applications. J. Mater. Chem. 2005, 15, 75–93. [Google Scholar] [CrossRef]
  155. Nakanishi, F.; Nakanishi, H.; Hasegawa, M.; Yamada, Y. Four-center type photopolymerization in the solid state. VII. Photochemical reaction of m-phenylene diacrylic acid dimethyl ester. J. Polym. Sci. Part A 1975, 13, 2499–2506. [Google Scholar]
  156. Nakanishi, H.; Sasada, Y. The crystal and molecular structure of dimethyl m-phenylenediacrylate. Bull. Chem. Soc. Jpn. 1977, 50, 3182–3185. [Google Scholar] [CrossRef]
  157. Chakrabarti, S.; Maity, A.K.; Misra, T.N. Spectroscopic study of solid-state photoreaction in organic crystal: Photopolymerization of dimethyl ester of α,α′-dicyano-p-phenylenediacrylic acid and diethyl ester of p-phenylenediacrylic acid. J. Polym. Sci. Part A 1992, 30, 1625–1631. [Google Scholar] [CrossRef]
  158. Minsk, L.M.; Smith, J.G.; Van Deusen, W.P.; Wright, J.F. Photosensitive polymers. I. Cinnamate esters of poly(vinyl alcohol) and cellulose. J. Appl. Polym. Sci. 1959, 2, 302–307. [Google Scholar] [CrossRef]
  159. Reiser, A.; Egerton, P.L. The mechanism of crosslink formation in solid polyvinylcinnamate and related photopolymers. Photogr. Sci. Eng. 1979, 23, 144–150. [Google Scholar]
  160. Ichimura, K. Preparation of water-soluble photoresist derived from poly(vinyl alcohol). J. Polym. Sci. Part A 1982, 20, 1411–1417. [Google Scholar]
  161. Ichimura, K.; Watanabe, S. Preparation and characteristics of photocrosslinkable poly(vinyl alcohol). J. Polym. Sci. Part A 1982, 20, 1419–1432. [Google Scholar]
  162. Ichimura, K.; Oohara, N. Photosensitive poly(methacrylates) having styrylpyridinium and styrylquinolinium groups. J. Polym. Sci. Part A 1987, 25, 3063–3077. [Google Scholar]
  163. Skloss, T.W.; Haw, J.F. Detection of cross-link formation by [2+2] photocycloaddition in poly(viny1 cinnamate) by 13C solid-state NMR. Macromolecules 1994, 27, 6998–6999. [Google Scholar] [CrossRef]
  164. Cockburn, E.S.; Davidson, R.S.; Pratt, J.E. The photocrosslinking of styrylpyridinium salts via a [2 + 2]-cycloaddition reaction. J. Photochem. Photobiol. A Chem. 1996, 94, 83–88. [Google Scholar] [CrossRef]
  165. Guo, M.; Xu, Z.; Wang, X. Photofabrication of two-dimensional quasi-crystal patterns on UV-curable molecular azo glass films. Langmuir 2008, 24, 2740–2745. [Google Scholar] [CrossRef]
  166. Chung, C.-M.; Roh, Y.-S.; Cho, S.-Y.; Kim, J.-G. Crack healing in polymeric materials via photochemical [2+2] cycloaddition. Chem. Mater. 2004, 16, 3982–3984. [Google Scholar] [CrossRef]
  167. Li, F.; Zhuang, J.; Jiang, G.; Tang, H.; Xia, A.; Jiang, L.; Song, Y.; Li, Y.; Zhu, D. A rewritable optical data storage material system by [2+2] photocycloreversion-photocycloaddition. Chem. Mater. 2008, 20, 1194–1196. [Google Scholar] [CrossRef]
  168. Chung, J.W.; You, Y.; Huh, H.S.; An, B.-K.; Yoon, S.-J.; Kim, S.H.; Lee, S.W.; Park, S.Y. Shear- and UV-induced fluorescence switching in stilbenic π-dimer crystals powered by reversible [2+2] cycloaddition. J. Am. Chem. Soc. 2009, 131, 8163–8172. [Google Scholar]
  169. Enkelmann, V.; Wegner, G. Novak, K.; Wagener, K.B. Single-crystal-to-single-crystal photodimerization of cinnamic acid. J. Am. Chem. Soc. 1993, 115, 10390–10391. [Google Scholar]
  170. Enkelmann, V.; Wegner, G.; Novak, K.; Wagener, K.B. Crystal-to-crystal photodimerizations. Mol. Cryst. Liq. Cryst. 1994, 240, 121–126. [Google Scholar] [CrossRef]
  171. Takahashi, S.; Miura, H.; Kasai, H.; Okada, S.; Oikawa, H.; Nakanishi, H. Single-crystal-to-single-crystal transformation of diolefin derivatives in nanocrystals. J. Am. Chem. Soc. 2002, 124, 10944–10945. [Google Scholar] [CrossRef]
  172. Bučar, D.-K.; MacGillivray, L.R. Preparation and reactivity of nanocrystalline cocrystals formed via sonocrystallization. J. Am. Chem. Soc. 2007, 129, 32–33. [Google Scholar] [CrossRef]

Share and Cite

MDPI and ACS Style

Sonoda, Y. Solid-State [2+2] Photodimerization and Photopolymerization of α,ω-Diarylpolyene Monomers: Effective Utilization of Noncovalent Intermolecular Interactions in Crystals. Molecules 2011, 16, 119-148. https://doi.org/10.3390/molecules16010119

AMA Style

Sonoda Y. Solid-State [2+2] Photodimerization and Photopolymerization of α,ω-Diarylpolyene Monomers: Effective Utilization of Noncovalent Intermolecular Interactions in Crystals. Molecules. 2011; 16(1):119-148. https://doi.org/10.3390/molecules16010119

Chicago/Turabian Style

Sonoda, Yoriko. 2011. "Solid-State [2+2] Photodimerization and Photopolymerization of α,ω-Diarylpolyene Monomers: Effective Utilization of Noncovalent Intermolecular Interactions in Crystals" Molecules 16, no. 1: 119-148. https://doi.org/10.3390/molecules16010119

Article Metrics

Back to TopTop