Next Article in Journal
Element Strategy Using Ru-Mn Substitution in CuO-CaCu3Ru4O12 Composite Ceramics with High Electrical Conductivity
Next Article in Special Issue
σ-Hole Interactions: Perspectives and Misconceptions
Previous Article in Journal
Dual Inhibition of AChE and BChE with the C-5 Substituted Derivative of Meldrum’s Acid: Synthesis, Structure Elucidation, and Molecular Docking Studies
Previous Article in Special Issue
On the Importance of Halogen–Halogen Interactions in the Solid State of Fullerene Halides: A Combined Theoretical and Crystallographic Study
 
 
Search for Articles:
Title / Keyword
Author / Affiliation / Email
Journal
Article Type
 
 
Advanced Search
 
Section
Special Issue
Volume
Issue
Number
Page
 
Journals
Crystals
Volume 7
Issue 7
10.3390/cryst7070214
crystals-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
first_page
settings
Order Article Reprints
Font Type:
Arial Georgia Verdana
Font Size:
Aa Aa Aa
Line Spacing:
Column Width:
Background:
Article

Halogen-Bonded Co-Crystals of Aromatic N-oxides: Polydentate Acceptors for Halogen and Hydrogen Bonds

by
Rakesh Puttreddy
*,
Filip Topić
,
Arto Valkonen
and
Kari Rissanen
*
Department of Chemistry, University of Jyvaskyla, P.O. Box 35, FI-40014 Jyvaskyla, Finland
*
Authors to whom correspondence should be addressed.
Crystals 2017, 7(7), 214; https://doi.org/10.3390/cryst7070214
Submission received: 7 June 2017 / Revised: 6 July 2017 / Accepted: 7 July 2017 / Published: 11 July 2017
(This article belongs to the Special Issue Analysis of Halogen and Other σ-Hole Bonds in Crystals)
Browse Figures
Versions Notes

Abstract

:
Seventeen new halogen-bonded co-crystals characterized by single crystal X-ray analysis are presented from 8 × 4 combinations using methyl-substituted pyridine N-oxides and 1,ω-diiodoperfluoroalkanes. The N−O group in six of 17 co-crystals is monodentate and 11 have μ-O,O bidentate halogen bond acceptor modes. Remarkably, the N−O group in co-crystals of 3-methyl-, 4-methyl- and 3,4-dimethylpyridine N-oxides with octafluoro-1,4-diiodobutane acted as a μ-O,O,O,O halogen and hydrogen bond acceptor, while acting as a μ-O,O,O acceptor in the co-crystal of 2,5-dimethylpyridine N-oxide and tetrafluoro-1,2-diiodoethane. The C−H···O−N hydrogen bonds demonstrated the polydentate cooperativity of the N−O group as a mixed halogen-hydrogen bond acceptor. The co-crystal of 2,4,6-trimethylpyridine N-oxide and dodecafluoro-1,6-diiodohexane exhibited C−I···O−−N+ halogen bonds with RXB value 0.76, the shortest of its kind compared to previously reported structures. The RXB values between 0.76 and 0.83 suggested that the C−I···O−−N+ halogen bonds are moderately strong compared to our previously studied N−−I+···O−−N+ system, with RXB in the order 0.66.

1. Introduction

The halogen bond (XB), analogous to the hydrogen bond (HB), has been defined [1] as a net attractive interaction between an electrophilic region of a halogen atom bound to a molecular entity and a nucleophilic site in another moiety, e.g., a nitrogen, oxygen or sulphur atom [2]. This region of positive electrostatic potential, called the “sigma hole” [3,4], is characteristic for halogen atoms attached to an organic backbone, with its magnitude generally decreasing in the order I > Br > Cl > F. Despite similar geometrical features between HB and XB, the halogen bond is still not as well-explored compared to the ubiquitous HB [5,6,7,8,9]. Halogen bonds are frequently studied using nitrogen compounds, which typically display monovalent N···X (X = I, Br) interactions and are well understood as crystal engineering tools for self-assembly processes. Their precedence from discrete structures to increased dimensionality through the controlled reactivity of substrates is well-reported [10,11,12,13]. In a solid-state XB complex, R−X···B−Z, where X is the donor and B is the acceptor atom, the ratio of the short distance between X and B atoms (dX-B) to sum of the Van der Waals radii of X and B atoms (dvdW) is defined as the normalized strength parameter, RXB = dX-B/dvdW [1]. Knowledge of RXB values provides an opportunity to roughly estimate the strengths of XB complexes. For example, the X···N distances in bis(pyridine)iodonium(I) tetrafluoroborate constitute an RXB value of 0.65, and such compounds are classified as halogen bonds of covalent nature [14]. Carefully designed nitrogen compounds are successfully utilized as molecular building blocks engaging in (N−X−N)⁺X− XBs to construct supramolecular structures resembling metal coordination frameworks [15]. However, weaker C−I···N XBs with typical RXB values ranging from 0.75 to 0.90 are still of considerable importance for applications in materials chemistry, e.g., for triggering liquid crystallinity and gelation behaviour [16,17,18].
Aromatic N-oxides have been long known in heterocyclic chemistry for functionalized pyridines syntheses [19,20,21,22,23,24,25]. Besides being valuable synthetic intermediates, the dipolar neutral N⁺−O− group exhibits a push-pull property towards aromatic rings, enabling it to undergo both electrophilic and nucleophilic substitution reactions, categorizing these compounds as promising building blocks in supramolecular chemistry [26,27]. Electron-donating and electron-withdrawing substituents on aromatic ring invoke different hybridization states on oxygen in the N−O group [28,29], allowing for tuning of its complexation behaviour towards metals [30,31].
Strategic exploitation of XB acceptor properties for heteroatoms, such as oxygen, remains very much unknown in the literature. A Cambridge Structural Database (CSD) search for pyridine N-oxides functioning as XB acceptors revealed only a handful of structures (see supporting information for more details), while their systematic investigations remain especially scarce [32,33,34]. Previously, monodentate strong N−−I+···O−−N+ XBs (RXB as low as 0.66) of coordinative nature between pyridine N-oxides and N-haloimides were studied both in solution and in the solid-state [35]. Here, we aimed to investigate C−I···O−−N+ XBs using 1,ω-diiodoperfluoroalkanes (DI2–DI8) and methyl-substituted aromatic N-oxides (1–8), as shown in Figure 1. Haloperfluoroalkanes are robust XB donors, and their ability to steer the supramolecular assembly by XBs and F···F interactions is well described [36]. However, the volatile nature of these compounds often results in oily or waxy substances, which are difficult to characterize using single crystal X-ray diffraction [18,37]. Despite their reluctance to crystallize, our attempts from 8 × 4 (acceptor × donor) combinations resulted in 17 crystal structures, providing an impressive crystallization success rate to analyze and understand the interactions at play in their solid-state structures.

2. Results and Discussion

The methods used to obtain the single crystals suitable for X-ray analysis are shown in Table S1. Co-crystals 1•DI6, 1•DI8, 2•DI4, 3•DI4, 3•DI8, 4•DI4_I, 4•DI4_II, 5•DI2, 5•DI6, 7•DI4 and 7•DI6 all form infinite 1-D polymers, and 4•DI4_I and 4•DI4_II are polymorphs. The co-crystals were grouped and discussed based on structural similarities observed in the crystal packing. Halogen bonds between N−O and C−I groups were explored as the driving force propagating 1-D polymers with alternate acceptors and donors. The XB interaction bond parameters are shown in Table 1. In 1•DI6, 1•DI8 and 3•DI8, the aromatic rings and donors were essentially coplanar, in contrast to the orthogonal alignment typically observed in coordination compounds [30,31]. The N−O groups were μ-O,O bidentate, bridging the donors to form remarkably similar 1-D polymeric chains, as shown in Figure 2. Further analysis of the crystal packing revealed the donor-acceptor parallel arrangement to be a result of F···F aggregation [38,39,40,41,42] between perfluorinated donor chains, which, though weaker than C−I···O−−N+ XBs, play a crucial role to yield a robust 3-D crystal structure.
The strength of the C−H···O interaction is approximately one-third of conventional HBs [43,44,45,46,47,48,49] that operate between donors such as −N−H/−O−H and weak bases, and these interactions significantly increase the lattice energy of the co-crystals [50]. The C−H···O contacts are attractive, and are rather site acidity-dependent. For example, the C2-proton acidity in pyridine N-oxides for ortho-C−H functionalization in organic synthesis [19,20,21,22,23,24,25], and in crystal engineering for C−H···O−N interactions is well studied [51,52,53,54]. However, to the best of our knowledge, the combination of C−H···O−N and C−I···O−N interactions through the N−O group, giving rise to supramolecular assemblies, has not been extensively studied. Co-crystals 3•DI4, 4•DI4_I, 7•DI4, and 7•DI6 all formed 1-D polymers driven majorly by C−I···O−N interactions; however, C−H···O interactions orthogonal to XB chains were interpreted as an essential element of the co-crystal structure. For example, in 3•DI4, the N−O group bridged donors at I···O distances of ca. 2.840 Å (RXB = 0.81) and ca. 2.875 Å (RXB = 0.82) with I···O···I angles of ca. 139.6°, leading to 1-D polymers. Orthogonal to μ-O,O XB mode, C−H···O interactions operated between N−O groups and C2-/C6-protons in the ab-plane to form 2-D sheets (Figure 3a). The perfluorinated chains and aromatic rings from adjacent 1-D polymers aggregated through F···F and C−H···O interactions, and induced segregation of donors and acceptors in the crystal structure. Similar ortho-C−H···O interactions between N-oxide molecules, and donor-acceptor segregated crystal packing motifs were observed in 4•DI4_I, 7•DI4 and 7•DI6 (Figure 3b–d).
Structures of co-crystals 2•DI4, 4•DI4_II, 5•DI2 and 5•DI6 showed 1-D undulating patterns driven by C−I···O−N interactions, as depicted in Figure 4. The I···O···I angles and the centroid-to-centroid distances between aromatic rings occupying the crest and trough sites were directly related. For example, the 2•DI4 (145.2°) and 4•DI4_II (112.2°) manifested a shallow wave appearance, with centroid-to-centroid aromatic distances of 23.2 Å and 19.2 Å, respectively. These I···O···I angles were greater than in 5•DI2 (103.6°) and 5•DI6 (107.8°), which both exhibited sharp interwoven patterns with the respective centroid-to-centroid aromatic distances of 16.9 Å and 17.2 Å. In 5•DI2 and 5•DI6, the aromatic rings were orthogonal to μ-O,O XB mode, favouring closer interdigitation between 1-D chains stabilized by C−H···F interactions. Moreover, the 1-D XB chains were cross-aligned in 2•DI4 (Figure 4b), different from parallel stack observed in 4•DI4_II, 5•DI2 and 5•DI6 (Figure 4f). In these structures, the aromatic rings did not participate in any π···π interactions, and the structures were sustained by several weak F···F, C−H···O and C−H···F interactions.
The N−O groups in co-crystals 7•DI2 and 7•DI8 act as monodentate XB acceptors with I···O distances ca. 2.703 Å (RXB = 0.77) and ca. 2.715 Å (RXB = 0.78). Contrary to above examples, the C−H···O interactions became more pronounced in 7•DI2 and 7•DI8, breaking the XB continuity in 1-D chains, and inducing alternate XB and cyclic C−H···O interactions as seen in Figure 5. The molecules of 7 could be seen as forming fully planar dimers, which were further connected by XB respectively with DI2 or DI8. In 7•DI2, the offset stacking of the acceptor dimers prevented the formation of F···F interactions by DI2 (Figure 5c). In 7•DI8, due to longer DI8 chains, the π···π stacking prevented only a half of the perfluorooctane chain from establishing F···F interactions (Figure 5d), with the packing in co-crystals 7•DI2 and 7•DI8 being otherwise quite similar.
The 6•DI2 exhibited a 1:2 donor-acceptor stoichiometry, crystallizing in the monoclinic space group P21/n, with the donor molecule DI2 lying on an inversion centre. A XB with I···O distances of ca. 2.714 (RXB = 0.78) and two C−H···O−N interactions at N−O group suggested sp3 hybridization of the oxygen. The C−H···O interactions played a significant role in the crystal packing. Analysis of the interlayer packing revealed the formation of a 1-D zig-zag HB tape along the b-axis (Figure 6a) through C−H···O interactions between the N−O group and the C2-methyl and C6-hydrogens. The 1-D tapes were connected by DI2 (Figure 6b) to give 2-D sheets which further stacked along the third dimension, with centroid-to-centroid aromatic distances of ca. 3.84 Å.
Co-crystals 5•DI4, 8•DI2 and 8•DI6 also formed 2:1 acceptor-donor discrete structures (Figure 7a–c), with monodentate XB acceptor modes for N−O groups. In 5•DI4, the 1:2 discrete units propagated along the b-axis by C−H···O interactions between N−O and methyl groups. Further, the 1-D motifs (Figure 7d) extended three dimensionally through C−H···F and π···π interactions. Co-crystal 8•DI2 had an interesting 1-D ladder structure (Figure 7f), with N-oxides forming 1-D tapes through C−H···O interactions as the side rails (Figure 7g) connected by halogen bonds via DI2. These 1-D ladders further packed through stacking of the aromatic rings as depicted schematically in Figure 7h. On the other hand, 8•DI6 with its 3:1 acceptor-donor generated a more complex structure, extended by π···π interactions between 2:1 discrete units and the additional, “passive” molecule of N-oxide 8, not involved in XB, as depicted in Figure 7e. While the “passive” molecule of 8, situated near an inversion centre, was disordered over two components with 50:50 occupancies, the anti-gauche conformation of DI6 was not compatible with the presence of an inversion centre in the middle of the C3-C4 bond of the donor.

3. Conclusions

Halogen bonding between pyridine N-oxides and 1,ω-diiodoperfluoroalkanes was found to be a reliable tool for crystal engineering, as witnessed by the successful structural characterization of 17 co-crystals reported here. The N-oxide functionality was able to act as either a monodentate (6/17 co-crystals) or μ-O,O bidentate (11/17 co-crystals) halogen bond acceptor. Monodentate C−I···O−−N+ halogen bonds were stronger than bidentate C−I···O−−N+ halogen bonds. Based on the observed RXB values, ranging from 0.76 to 0.83, C−I···O−−N+ halogen bonds can be classified as moderately strong compared to e.g. very strong monodentate N−−I+···O−−N+ type halogen bonds, previously studied by us, which display RXB values as low as 0.66. In addition to that, an important role of weak interactions, such as weak C−H···O hydrogen bonds and aromatic ring stacking, has been established. In particular, the N-oxide oxygen atom was shown to simultaneously engage in both the hydrogen and halogen bonding as a mixed acceptor. However, the C−H···O hydrogen bonds were fairly weak, as witnessed by the observation of two polymorphs of 4•DI4, where only one of the two exhibited C−H···O hydrogen bonds. The ability of N-oxide oxygen to act as a μ2- (one XB and one HB), μ3- (one XB and two HB) and μ4-acceptor (two XB and two HB) is a complex process. For example, the pronounced C−H···O hydrogen bonds between N-oxide oxygen and C2- acidic protons can be a result of F···F interaction [38,39,40,41,42] between adjacent perfluorinated donor chains, resulting in a stable crystal lattice.

4. Materials and Instrumentation

All solvents used for crystal growth were of reagent grade, and used as received. Pyridine N-oxide (1), 2-methylpyridine N-oxide (2), 3-methylpyridine N-oxide (3), 4-methylpyridine N-oxide (4), 2,6-dimethylpyridine N-oxide (5) and hexadecafluoro-1,8-diiodooctane (DI8) were purchased from Sigma-Aldrich, while tetrafluoro-1,2-ethane (DI2), octafluoro-1,4-diiodobutane (DI4), and dodecafluoro-1,6-diiodohexane (DI6) were purchased from Apollo Scientific Chemicals Ltd. 2,5-Dimethylpyridine N-oxide (6), 3,4-dimethylpyridine N-oxide (7) and 2,4,6-trimethylpyridine N-oxide (8) were synthesized as previously reported [29].
Single crystal X-ray data for 1•DI6, 1•DI8, 2•DI4, 3•DI4, 4•DI4_I, 4•DI4_II, 5•DI4, 7•DI2, 7•DI4, 7•DI6 and 8•DI2 were measured on a Bruker-Nonius Kappa CCD diffractometer (Bruker AXS Inc, Wisconsin, USA) with an APEX-II CCD detector using graphite-monochromated Mo-Kα (λ = 0.71073 Å) radiation. The data for 3•DI8, 5•DI2, 5•DI6, 6•DI2, 7•DI8, and 8•DI6 were measured on an RigakuOxford single-source diffractometer (Rigaku Corporation, Tokyo, Japan) equipped with an Eos CCD detector using mirror-monochromated Mo-Kα (λ = 0.71073 Å) radiation. The crystal data and experimental details for the data collections are given in Tables S2–S5. Data collection and reduction for Rigaku Oxford diffractometer were performed using the program CrysAlisPro [55], while for Bruker-Nonius Kappa CCD diffractometer using the program COLLECT [56] and HKL DENZO AND SCALEPACK [57]. A Gaussian face indexing-based absorption correction method [55] was used for 3•DI8, 5•DI2, 5•DI6 and 7•DI8, while the multi-scan absorption correction through CrysAlisPro [55] was used for 8•DI6 and through SADABS [58] for 1•DI6, 1•DI8, 2•DI4, 3•DI4, 4•DI4_I, 4•DI4_II, 5•DI4, 6•DI2, 7•DI2, 7•DI4, 7•DI6 and 8•DI2. The structures were solved with direct methods (either SHELXS or SHELXT) [59] and refined by full-matrix least squares on F2 using OLEX2 [60] and/or WinGX [61] which utilize the SHELXL-2016/6 module [59]. No attempt was made to locate the hydrogens from difference electron density Fourier maps, and appropriate constraints and restraints were used when necessary for disordered molecules.

Supplementary Materials

The following are available online at www.mdpi.com/2073-4352/7/7/214/s1, Table S1: Summary of crystallization experiments, Table S2: Crystal data and X-ray experimental details for 1•DI4–3•DI8, Table S3: Crystal data and X-ray experimental details for 4•DI4_I–5•DI6. Table S4: Crystal data and X-ray experimental details for 6•DI2–7•DI8. Table S5: Crystal data and X-ray experimental details for 8•DI2 and 8•DI6. Figure S1: Scatter plot of N-O···I angles vs. I···O distances in N-oxide oxygens functioning as halogen bond acceptors, as found in CCDC. Figure S2: Scatter plot of N−O···I angles vs. I···O distances as a comparison of our previous and current results of N-oxide oxygens functioning as halogen bond acceptors.

Acknowledgments

The authors kindly acknowledge the Academy of Finland (Project numbers RP: 298817, KR: 263256, 265328 and 292746) and the University of Jyväskylä for financial support.

Author Contributions

The synthesis of aromatic N-oxides and the project design presented in this work were performed by R.P. X-ray analysis and structural solution for eight structures was obtained by R.P., eight by F.T. and one by A.V. The manuscript was written by R.P. and assisted by F.T., and K.R. supervised the work.

Conflicts of Interest

The authors declare no conflict of interest.

References and Notes

  1. Desiraju, R.G.; Ho, S.P.; Kloo, L.; Legon, C.A.; Marquardt, R.; Metrangolo, P.; Politzer, P.; Resnati, G.; Rissanen, K. Definition of the halogen bond (IUPAC Recommendations 2013). Pure Appl. Chem. 2013, 85, 1711–1713. [Google Scholar] [CrossRef]
  2. Halogen Bonding, 2008th ed.; Metrangolo, P.; Resnati, G. (Eds.) Springer: Berlin, Germany, 2008; Volume 126. [Google Scholar]
  3. Politzer, P.; Murray, J.S. Halogen bonding: An interim discussion. ChemPhysChem 2013, 14, 278–294. [Google Scholar] [CrossRef] [PubMed]
  4. Politzer, P.; Murray, J.S.; Clark, T. Halogen bonding and other [sigma]-hole interactions: A perspective. Phys. Chem. Chem. Phys. 2013, 15, 11178–11189. [Google Scholar] [CrossRef] [PubMed]
  5. Rissanen, K. Halogen bonded supramolecular complexes and networks. CrystEngComm 2008, 10, 1107–1113. [Google Scholar] [CrossRef]
  6. Troff, R.W.; Mäkelä, T.; Topić, F.; Valkonen, A.; Raatikainen, K.; Rissanen, K. Alternative motifs for halogen bonding. Eur. J. Org. Chem. 2013, 2013, 1617–1637. [Google Scholar] [CrossRef]
  7. Metrangolo, P.; Meyer, F.; Pilati, T.; Resnati, G.; Terraneo, G. Halogen bonding in supramolecular chemistry. Angew. Chem. Int. Ed. 2008, 47, 6114–6127. [Google Scholar] [CrossRef] [PubMed]
  8. Priimagi, A.; Cavallo, G.; Metrangolo, P.; Resnati, G. The halogen bond in the design of functional supramolecular materials: Recent advances. Acc. Chem. Res. 2013, 46, 2686–2695. [Google Scholar] [CrossRef] [PubMed]
  9. Voth, A.R.; Khuu, P.; Oishi, K.; Ho, P.S. Halogen bonds as orthogonal molecular interactions to hydrogen bonds. Nat. Chem. 2009, 1, 74–79. [Google Scholar] [CrossRef] [PubMed]
  10. Bedin, M.; Karim, A.; Reitti, M.; Carlsson, A.-C.C.; Topić, F.; Cetina, M.; Pan, F.; Havel, V.; Al-Ameri, F.; Sindelar, V.; et al. Counterion influence on the [N-I-N]+ halogen bond. Chem. Sci. 2015, 6, 3746–3756. [Google Scholar] [CrossRef]
  11. Carlsson, A.-C.C.; Gräfenstein, J.; Budnjo, A.; Laurila, J.L.; Bergquist, J.; Karim, A.; Kleinmaier, R.; Brath, U.; Erdélyi, M. Symmetric halogen bonding is preferred in solution. J. Am. Chem. Soc. 2012, 134, 5706–5715. [Google Scholar] [CrossRef] [PubMed]
  12. Carlsson, A.-C.C.; Veiga, A.; Erdélyi, M. Halogen bonding in solution. In Halogen Bonding II SE-607; Metrangolo, P., Resnati, G., Eds.; Springer: Berlin, Germany, 2015; Volume 359, pp. 49–76. [Google Scholar]
  13. Rissanen, K.; Haukka, M. Halonium Ions as Halogen Bond Donors in the Solid State [XL2]Y Complexes. In Halogen Bonding II SE-587; Metrangolo, P., Resnati, G., Eds.; Springer: Berlin, Germany, 2015; Volume 359, pp. 77–90. [Google Scholar]
  14. Barluenga, J.; González, J.M.; Campos, P.J.; Asensio, G. I(Py)2BF4, a new reagent in organic synthesis: General method for the 1,2-Iodofunctionalization of olefins. Angew. Chem. Int. Ed. 1985, 24, 319–320. [Google Scholar] [CrossRef]
  15. Turunen, L.; Warzok, U.; Puttreddy, R.; Beyeh, N.K.; Schalley, C.A.; Rissanen, K. [N⋅⋅⋅I+⋅⋅⋅N] halogen-bonded dimeric capsules from tetrakis(3-pyridyl)ethylene cavitands. Angew. Chem. Int. Ed. 2016, 55, 14033–14036. [Google Scholar] [CrossRef] [PubMed]
  16. Fourmigué, M. Halogen bonding: Recent advances. Curr. Opin. Solid State Mater. Sci. 2009, 13, 36–45. [Google Scholar] [CrossRef]
  17. Nguyen, H.L.; Horton, P.N.; Hursthouse, M.B.; Legon, A.C.; Bruce, D.W. Halogen bonding: A new interaction for liquid crystal formation. J. Am. Chem. Soc. 2004, 126, 16–17. [Google Scholar] [CrossRef] [PubMed]
  18. Metrangolo, P.; Prasang, C.; Resnati, G.; Liantonio, R.; Whitwood, A.C.; Bruce, D.W. Fluorinated liquid crystals formed by halogen bonding. Chem. Commun. 2006, 3290–3292. [Google Scholar] [CrossRef] [PubMed]
  19. Bull, J.A.; Mousseau, J.J.; Pelletier, G.; Charette, A.B. Synthesis of pyridine and dihydropyridine derivatives by regio- and stereoselective addition to N-activated pyridines. Chem. Rev. 2012, 112, 2642–2713. [Google Scholar] [CrossRef] [PubMed]
  20. Xiao, B.; Liu, Z.-J.; Liu, L.; Fu, Y. Palladium-catalyzed C–H activation/cross-coupling of pyridine N-oxides with nonactivated secondary alkyl bromides. J. Am. Chem. Soc. 2013, 135, 616–619. [Google Scholar] [CrossRef] [PubMed]
  21. Wu, J.; Cui, X.; Chen, L.; Jiang, G.; Wu, Y. Palladium-catalyzed alkenylation of quinoline-N-oxides via C−H activation under external-oxidant-free conditions. J. Am. Chem. Soc. 2009, 131, 13888–13889. [Google Scholar] [CrossRef] [PubMed]
  22. Campeau, L.-C.; Schipper, D.J.; Fagnou, K. Site-selective sp2 and benzylic sp3 palladium-catalyzed direct arylation. J. Am. Chem. Soc. 2008, 130, 3266–3267. [Google Scholar] [CrossRef] [PubMed]
  23. Campeau, L.-C.; Bertrand-Laperle, M.; Leclerc, J.-P.; Villemure, E.; Gorelsky, S.; Fagnou, K. C2, C5, and C4 azole N-oxide direct arylation including room-temperature reactions. J. Am. Chem. Soc. 2008, 130, 3276–3277. [Google Scholar] [CrossRef] [PubMed]
  24. Pool, J.A.; Scott, B.L.; Kiplinger, J.L. A new mode of reactivity for pyridine N-oxide: C−H activation with uranium(IV) and thorium(IV) bis(alkyl) complexes. J. Am. Chem. Soc. 2005, 127, 1338–1339. [Google Scholar] [CrossRef] [PubMed]
  25. Campeau, L.-C.; Rousseaux, S.; Fagnou, K. A solution to the 2-Pyridyl organometallic cross-coupling problem: Regioselective catalytic direct arylation of pyridine N-oxides. J. Am. Chem. Soc. 2005, 127, 18020–18021. [Google Scholar] [CrossRef] [PubMed]
  26. Adriaenssens, L.; Ballester, P. Hydrogen bonded supramolecular capsules with functionalized interiors: The controlled orientation of included guests. Chem. Soc. Rev. 2013, 42, 3261–3277. [Google Scholar] [CrossRef] [PubMed]
  27. Raynal, M.; Ballester, P.; Vidal-Ferran, A.; van Leeuwen, P.W. Supramolecular catalysis. Part 1: Non-covalent interactions as a tool for building and modifying homogeneous catalysts. Chem. Soc. Rev. 2014, 43, 1660–1733. [Google Scholar] [CrossRef] [PubMed]
  28. Albini, A. Heterocyclic N-oxides; CRC Press: Boca Raton, FL, USA, 1991. [Google Scholar]
  29. Katritzky, A.R.; Lagowski, J.M. Chemistry of the Heterocyclic N-oxides; Academic Press: Cambridge, MA, USA, 1971. [Google Scholar]
  30. Puttreddy, R.; Steel, P.J. 4-Methoxypyridine N-oxide: An electron-rich ligand that can simultaneously bridge three silver atoms. Inorg. Chem. Commun. 2014, 41, 33–36. [Google Scholar] [CrossRef]
  31. Puttreddy, R.; Steel, P.J. Pyridine N-oxide: A hyperdentate argentophile. CrystEngComm 2014, 16, 556–560. [Google Scholar] [CrossRef]
  32. Pang, X.; Jin, W.J. Exploring the halogen bond specific solvent effects in halogenated solvent systems by ESR probe. New J. Chem. 2015, 39, 5477–5483. [Google Scholar] [CrossRef]
  33. Aakeröy, C.B.; Wijethunga, T.K.; Desper, J. Constructing molecular polygons using halogen bonding and bifurcated N-oxides. CrystEngComm 2014, 16, 28–31. [Google Scholar] [CrossRef]
  34. Messina, M.T.; Metrangolo, P.; Panzeri, W.; Pilati, T.; Resnati, G. Intermolecular recognition between hydrocarbon oxygen-donors and perfluorocarbon iodine-acceptors: The shortest O⋯I non-covalent bond. Tetrahedron 2001, 57, 8543–8550. [Google Scholar] [CrossRef]
  35. Puttreddy, R.; Jurček, O.; Bhowmik, S.; Makela, T.; Rissanen, K. Very strong -N-X+···−O-N+ halogen bonds. Chem. Commun. 2016, 11, 2338–2341. [Google Scholar] [CrossRef] [PubMed]
  36. Ho, P.S. Halogen Bonding I. Top. Curr. Chem. 2015, 358, 241–276. [Google Scholar] [PubMed]
  37. Aakeröy, C.B.; Wijethunga, T.K.; Benton, J.; Desper, J. Stabilizing volatile liquid chemicals using co-crystallization. Chem. Commun. 2015, 51, 2425–2428. [Google Scholar] [CrossRef] [PubMed]
  38. Omorodion, H.; Twamley, B.; Platts, J.A.; Baker, R.J. Further evidence on the importance of fluorous–fluorous interactions in supramolecular chemistry: A combined structural and computational study. Cryst. Growth Des. 2015, 15, 2835–2841. [Google Scholar] [CrossRef]
  39. Baker, R.J.; Colavita, P.E.; Murphy, D.M.; Platts, J.A.; Wallis, J.D. Fluorine–fluorine interactions in the solid state: An experimental and theoretical study. J. Phys. Chem. A 2012, 116, 1435–1444. [Google Scholar] [CrossRef] [PubMed]
  40. Reichenbacher, K.; Suss, H.I.; Hulliger, J. Fluorine in crystal engineering—“The little atom that could”. Chem. Soc. Rev. 2005, 34, 22–30. [Google Scholar] [CrossRef] [PubMed]
  41. O’Hagan, D. Understanding organofluorine chemistry. An introduction to the C–F bond. Chem. Soc. Rev. 2008, 37, 308–319. [Google Scholar] [CrossRef] [PubMed]
  42. Berger, R.; Resnati, G.; Metrangolo, P.; Weber, E.; Hulliger, J. Organic fluorine compounds: A great opportunity for enhanced materials properties. Chem. Soc. Rev. 2011, 40, 3496–3508. [Google Scholar] [CrossRef] [PubMed]
  43. Taylor, R. It Isn’t, It Is: The C–H···X (X = O, N, F, Cl) interaction really is significant in crystal packing. Cryst. Growth Des. 2016, 16, 4165–4168. [Google Scholar] [CrossRef]
  44. Dragelj, J.L.; Stanković, I.M.; Božinovski, D.M.; Meyer, T.; Veljković, D.Ž.; Medaković, V.B.; Knapp, E.-W.; Zarić, S.D. C–H/O interactions of aromatic CH donors within proteins: A crystallographic study. Cryst. Growth Des. 2016, 16, 1948–1957. [Google Scholar] [CrossRef]
  45. Ji, W.; Liu, G.; Li, Z.; Feng, C. Influence of C–H···O hydrogen bonds on macroscopic properties of supramolecular assembly. ACS Appl. Mater. Interfaces 2016, 8, 5188–5195. [Google Scholar] [CrossRef] [PubMed]
  46. Jones, C.R.; Baruah, P.K.; Thompson, A.L.; Scheiner, S.; Smith, M.D. Can a C–H···O interaction be a determinant of conformation? J. Am. Chem. Soc. 2012, 134, 12064–12071. [Google Scholar] [CrossRef] [PubMed]
  47. Gu, Y.; Kar, T.; Scheiner, S. Fundamental properties of the C–H···O interaction: Is it a true hydrogen bond? J. Am. Chem. Soc. 1999, 121, 9411–9422. [Google Scholar] [CrossRef]
  48. Jiang, L.; Lai, L. C–H···O hydrogen bonds at protein-protein interfaces. J. Biol. Chem. 2002, 277, 37732–37740. [Google Scholar] [CrossRef] [PubMed]
  49. Scheiner, S. Dissection of the factors affecting formation of a C–H∙∙∙O–H-bond. A Case Study. Crystals 2015, 5, 327–345. [Google Scholar] [CrossRef]
  50. Desiraju, G.R.; Vittal, J.J.; Ramanan, A. Crystal Engineering: A Textbook; World Scientific: Singapore, 2011. [Google Scholar]
  51. Babu, N.J.; Reddy, L.S.; Nangia, A. AmideN-oxide heterosynthon and amide dimer homosynthon in cocrystals of carboxamide drugs and pyridine N-oxides. Mol. Pharm. 2007, 4, 417–434. [Google Scholar] [CrossRef] [PubMed]
  52. Goud, N.R.; Babu, N.J.; Nangia, A. Sulfonamide-pyridinen-N-oxide cocrystals. Cryst. Growth Des. 2011, 11, 1930–1939. [Google Scholar] [CrossRef]
  53. Reddy, L.S.; Babu, N.J.; Nangia, A. Carboxamide-pyridine N-oxide heterosynthon for crystal engineering and pharmaceutical cocrystals. Chem. Commun. 2006, 1369–1371. [Google Scholar] [CrossRef] [PubMed]
  54. Puttreddy, R.; Cottam, J.R.A.; Steel, P.J. Anion dependent silver(I) complexes of pyrazine mono-N-oxide. RSC Adv. 2014, 4, 22449–22454. [Google Scholar] [CrossRef]
  55. Rigaku Oxford Diffr. 2016; Version 1.171.38.41.
  56. Bruker AXS BV. Madison, WI, USA, 1997–2004.
  57. Otwinowski, Z.; Minor, W. Processing of X-ray diffraction data collected in oscillation mode. Methods Enzymol. 1997, 276, 307–326. [Google Scholar] [PubMed]
  58. Blessing, R.H. Outlier treatment in data merging. J. Appl. Crystallogr. 1997, 30, 421–426. [Google Scholar] [CrossRef]
  59. Sheldrick, G.M. Crystal structure refinement with SHELXL. Acta Crystallogr. Sect. C 2015, 71, 3–8. [Google Scholar] [CrossRef] [PubMed]
  60. Dolomanov, O.V.; Bourhis, L.J.; Gildea, R.J.; Howard, J.A.K.; Puschmann, H. OLEX2: A complete structure solution, refinement and analysis program. J. Appl. Crystallogr. 2009, 42, 339–341. [Google Scholar] [CrossRef]
  61. Farrugia, L.J. WinGX and ORTEP for Windows: An update. J. Appl. Crystallogr. 2012, 45, 849–854. [Google Scholar] [CrossRef]
Crystals 07 00214 g001 550
Figure 1. The chemical structures of acceptors (top) and donors (below) in the current study: pyridine N-oxide (1), 2-methylpyridine N-oxide (2), 3-methylpyridine N-oxide (3), 4-methylpyridine N-oxide (4), 2,6-dimethylpyridine N-oxide (5), 2,5-dimethylpyridine N-oxide (6), 3,4-dimethylpyridine N-oxide (7), 2,4,6-trimethylpyridine N-oxide (8), tetrafluoro-1,2-diiodoethane (DI2), octafluoro-1,4-diiodobutane (DI4), dodecafluoro-1,6-diiodohexane (DI6) and hexadecafluoro-1,8-diiodooctane (DI8).
Figure 1. The chemical structures of acceptors (top) and donors (below) in the current study: pyridine N-oxide (1), 2-methylpyridine N-oxide (2), 3-methylpyridine N-oxide (3), 4-methylpyridine N-oxide (4), 2,6-dimethylpyridine N-oxide (5), 2,5-dimethylpyridine N-oxide (6), 3,4-dimethylpyridine N-oxide (7), 2,4,6-trimethylpyridine N-oxide (8), tetrafluoro-1,2-diiodoethane (DI2), octafluoro-1,4-diiodobutane (DI4), dodecafluoro-1,6-diiodohexane (DI6) and hexadecafluoro-1,8-diiodooctane (DI8).
Crystals 07 00214 g001
Crystals 07 00214 g002 550
Figure 2. Section of the crystal packing showing structural similarity between 1-D parallel stacks in 1•DI6 (a), 1•DI8 (b) and 3•DI8 (c).
Figure 2. Section of the crystal packing showing structural similarity between 1-D parallel stacks in 1•DI6 (a), 1•DI8 (b) and 3•DI8 (c).
Crystals 07 00214 g002
Crystals 07 00214 g003 550
Figure 3. 1-D Halogen bond polymers stitched by adjacent ortho-C−H···O interactions in, 3•DI4 (a), 4•DI4_I (b), 7•DI4 (c) and 7•DI6 (d) shown in capped stick models. Black and red broken lines are respectively XB and HB interactions.
Figure 3. 1-D Halogen bond polymers stitched by adjacent ortho-C−H···O interactions in, 3•DI4 (a), 4•DI4_I (b), 7•DI4 (c) and 7•DI6 (d) shown in capped stick models. Black and red broken lines are respectively XB and HB interactions.
Crystals 07 00214 g003
Crystals 07 00214 g004 550
Figure 4. Interwoven by C−H···F interactions, the 1-D undulated XB polymeric chains in 2•DI4 (a), 4•DI4_II (c), 5•DI6 (d) and 5•DI2 (e). Section of 3-D crystal packing in 2•DI4 (b) showing cross stack of 1-D polymers, and common parallel 1-D stack motifs observed in 4•DI4_II, 5•DI6 and 5•DI2 (f).
Figure 4. Interwoven by C−H···F interactions, the 1-D undulated XB polymeric chains in 2•DI4 (a), 4•DI4_II (c), 5•DI6 (d) and 5•DI2 (e). Section of 3-D crystal packing in 2•DI4 (b) showing cross stack of 1-D polymers, and common parallel 1-D stack motifs observed in 4•DI4_II, 5•DI6 and 5•DI2 (f).
Crystals 07 00214 g004
Crystals 07 00214 g005 550
Figure 5. 1-D Chains propagated by alternating XB and C−H···O interactions in 7•DI2 (a) and 7•DI8 (b). Section of crystal packing displaying isolated DI2 in 7•DI2 (c), and partially F···F stabilized DI8 in 7•DI8 (d). Black and red broken lines are respectively XB and HB interactions.
Figure 5. 1-D Chains propagated by alternating XB and C−H···O interactions in 7•DI2 (a) and 7•DI8 (b). Section of crystal packing displaying isolated DI2 in 7•DI2 (c), and partially F···F stabilized DI8 in 7•DI8 (d). Black and red broken lines are respectively XB and HB interactions.
Crystals 07 00214 g005
Crystals 07 00214 g006 550
Figure 6. The 1-D Hydrogen bond tapes bridged by DI2 donors (a), and a view along the b-axis showing connecting modes of DI2 (b). Color representation: Gold capped sticks are DI2 donors, black and red broken lines are respectively XB and HB interactions.
Figure 6. The 1-D Hydrogen bond tapes bridged by DI2 donors (a), and a view along the b-axis showing connecting modes of DI2 (b). Color representation: Gold capped sticks are DI2 donors, black and red broken lines are respectively XB and HB interactions.
Crystals 07 00214 g006
Crystals 07 00214 g007 550
Figure 7. 2:1 Acceptor-donor discrete structures in 5•DI4 (a) 8•DI2 (b) and 8•DI6 (c). The C−H···O interactions connect the 2:1 units in 5•DI4 (d). Complex crystal packing in 8•DI6 displaying π···π interactions stabilized 2:1 units (e); 1-D Ladder motif in 8•DI2 (f), and the 1-D HB tapes formed by 8 (g). Cartoon of 1-D ladders illustrating the π-π stacking in 8•DI2 (h). Black and red broken lines are respectively XB and HB interactions.
Figure 7. 2:1 Acceptor-donor discrete structures in 5•DI4 (a) 8•DI2 (b) and 8•DI6 (c). The C−H···O interactions connect the 2:1 units in 5•DI4 (d). Complex crystal packing in 8•DI6 displaying π···π interactions stabilized 2:1 units (e); 1-D Ladder motif in 8•DI2 (f), and the 1-D HB tapes formed by 8 (g). Cartoon of 1-D ladders illustrating the π-π stacking in 8•DI2 (h). Black and red broken lines are respectively XB and HB interactions.
Crystals 07 00214 g007
Table
Table 1. Bond parameters for co-crystals 1•DI6–8•DI6.
Table 1. Bond parameters for co-crystals 1•DI6–8•DI6.
S.NoCodeMonodentateμ-O,O
ca. d(I···O−N)/Å *Ð(C−I···O)/°ca. d(I···O−N)/Å *Ð(C−I···O)/°
11•DI62.834 [0.81]177.1****
21•DI82.833 [0.81]177.7****
32•DI42.747 [0.79]174.22.861 [0.82]178.9
43•DI42.840 [0.81]172.12.875 [0.82]168.8
53•DI82.809 [0.80]174.82.817 [0.81]174.7
64•DI4_I2.808 [0.80] ***172.3 ***2.813 [0.80] ***174.1 ***
74•DI4_II2.766 [0.79]177.5 *******
85•DI22.743 [0.78]161.2 *******
95•DI42.669 [0.76]171.3 ***----
105•DI62.733 [0.78]175.52.774 [0.80]169.0
2.764 [0.79]174.92.813 [0.804]170.3
116•DI22.714 [0.78]171.9----
127•DI22.703 [0.77]174.6----
137•DI42.835 [0.81]167.5 ***2.906 [0.83]170.0 ***
147•DI62.825 [0.81]167.9 ***2.827 [0.81]178.2 ***
157•DI82.715 [0.78]176.5----
168•DI22.702 [0.78]166.4----
2.775 [0.79]170.8----
178•DI62.649 [0.76]174.3----
2.682 [0.77]176.1----
* Respective RXB values are reported in parentheses [1]. ** The other halogen bond is symmetrically equivalent. *** Major disorder component.

Share and Cite

MDPI and ACS Style

Puttreddy, R.; Topić, F.; Valkonen, A.; Rissanen, K. Halogen-Bonded Co-Crystals of Aromatic N-oxides: Polydentate Acceptors for Halogen and Hydrogen Bonds. Crystals 2017, 7, 214. https://doi.org/10.3390/cryst7070214

AMA Style

Puttreddy R, Topić F, Valkonen A, Rissanen K. Halogen-Bonded Co-Crystals of Aromatic N-oxides: Polydentate Acceptors for Halogen and Hydrogen Bonds. Crystals. 2017; 7(7):214. https://doi.org/10.3390/cryst7070214

Chicago/Turabian Style

Puttreddy, Rakesh, Filip Topić, Arto Valkonen, and Kari Rissanen. 2017. "Halogen-Bonded Co-Crystals of Aromatic N-oxides: Polydentate Acceptors for Halogen and Hydrogen Bonds" Crystals 7, no. 7: 214. https://doi.org/10.3390/cryst7070214

APA Style

Puttreddy, R., Topić, F., Valkonen, A., & Rissanen, K. (2017). Halogen-Bonded Co-Crystals of Aromatic N-oxides: Polydentate Acceptors for Halogen and Hydrogen Bonds. Crystals, 7(7), 214. https://doi.org/10.3390/cryst7070214

Note that from the first issue of 2016, this journal uses article numbers instead of page numbers. See further details here.

Article Metrics

Back to TopTop