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Special Issue "New Trends in Photochemistry"

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A special issue of Molecules (ISSN 1420-3049).

Deadline for manuscript submissions: closed (31 December 2012)

Special Issue Editor

Guest Editor
Prof. Dr. Axel G. Griesbeck

Department of Chemistry, University of Cologne, Greinstr. 4, D-50939 Koeln, Germany
Website | E-Mail
Interests: photooxygenation of organic compounds; photocycloaddition reactions; photodecarboxylation; photoisomerization; photoinduced electron transfer; photochemical macrocyclization reactions; new photochemical reactors and technologies

Special Issue Information

Dear Colleagues,

Photochemical reactions are versatile processes for inorganic and organic syntheses. Synthesis using light as reagent and producing complex molecules from simple starting materials is exemplary realized in natural photosynthesis. Mankind still struggles for an efficient molecular system that mimics the natural process. In order to harvest light energy and to transform it into chemical energy, photochemical reactions have to be studied and optimized for synthetic applications. In recent years, photocatalysis has regained momentum because it combines the well established concepts of metalcatalysis and organocatalysis with the ideas of photoinduced electron transfer.  Altogether, photo redox catalysis will be one of the major topics in modern photochemistry of the next decades. Nonetheless, also traditional photochemical reactions such as photocycloadditions and -cyclizations,
photochemical rearrangements, photoreductions, photooxidations and -oxygenations, photoinduced group transfer reactions and applications of photoremovable protecting groups, photochromic systems or photodegradation processes have to be studied and develop in the future
in order to satisfy the needs for a more sustainable synthetic chemistry.

This special issue of Molecules welcomes previously unpublished manuscripts covering all aspects of photochemical reactions including their design, product assessment, methodology development and applications.

Prof. Dr. Axel G. Griesbeck
Guest Editor

Keywords

  • photocycloadditions
  • photochemical rearrangements
  • photoreduction
  • photooxidation
  • photooxygenation
  • photocatalysis
  • photochemical electron transfer
  • photoredox catalysis

Published Papers (7 papers)

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Research

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Open AccessArticle Photophysical Studies of a New Water Soluble Indocarbocyanine Dye Adsorbed onto Microcrystalline Cellulose and beta-Cyclodextrin
Molecules 2013, 18(5), 5648-5668; doi:10.3390/molecules18055648
Received: 21 January 2013 / Revised: 26 April 2013 / Accepted: 9 May 2013 / Published: 15 May 2013
Cited by 3 | PDF Full-text (1001 KB) | HTML Full-text | XML Full-text
Abstract
A water-soluble indocarbocyanine dye was synthesized and its photophysics were studied for the first time on two solid hosts, microcrystalline cellulose and b-cyclodextrin, as well as in homogeneous media. The inclusion of the indocarbocyanine moiety onto microcrystalline cellulose increased the dye aggregation with
[...] Read more.
A water-soluble indocarbocyanine dye was synthesized and its photophysics were studied for the first time on two solid hosts, microcrystalline cellulose and b-cyclodextrin, as well as in homogeneous media. The inclusion of the indocarbocyanine moiety onto microcrystalline cellulose increased the dye aggregation with both H and J aggregates being formed. Adsorption on b-cyclodextrin enhanced aggregation in a similar way. The fluorescence quantum yields were determined for the powdered samples of the cyanine dye on the two hosts and a significant increase was observed relative to homogeneous solution. A remarkable concentration dependence was also detected in both cases. A lifetime distribution analysis has shown that the indocarbocyanine dye mainly occupies the amorphous part of cellulose and is not entrapped in the crystalline part of this host. In the b-CD case, the adsorption occurs outside the host cavity. In both hosts a strong concentration quenching effect is observed and only monomers emit. Both adsorptions may be explained by stereochemical constraints imposed by the two long sulphoethyl tails linked to nitrogen atoms of the indocarbocyanine dye. Full article
(This article belongs to the Special Issue New Trends in Photochemistry)
Open AccessArticle Singlet Oxygen in Antimicrobial Photodynamic Therapy: Photosensitizer-Dependent Production and Decay in E. coli
Molecules 2013, 18(3), 2712-2725; doi:10.3390/molecules18032712
Received: 25 January 2013 / Revised: 19 February 2013 / Accepted: 21 February 2013 / Published: 28 February 2013
Cited by 18 | PDF Full-text (506 KB) | HTML Full-text | XML Full-text
Abstract
Several families of photosensitizers are currently being scrutinized for antimicrobial photodynamic therapy applications. Differences in physical and photochemical properties can lead to different localization patterns as well as differences in singlet oxygen production and decay when the photosensitizers are taken up by bacterial
[...] Read more.
Several families of photosensitizers are currently being scrutinized for antimicrobial photodynamic therapy applications. Differences in physical and photochemical properties can lead to different localization patterns as well as differences in singlet oxygen production and decay when the photosensitizers are taken up by bacterial cells. We have examined the production and fate of singlet oxygen in Escherichia coli upon photosensitization with three structurally-different cationic photosensitizers, namely New Methylene Blue N (NMB), a member of the phenothiazine family, ACS268, a hydrophobic porphyrin with a single cationic alkyl chain, and zinc(II)-tetramethyltetrapyridinoporphyrazinium salt, a phthalocyanine-like photosensitizer with four positive charges on the macrocycle core. The kinetics of singlet oxygen production and decay indicate different localization for the three photosensitizers, whereby NMB appears to localize in an aqueous-like microenvironment, whereas ACS268 localizes in an oxygen-shielded site, highly reactive towards singlet oxygen. The tetracationic zinc(II) tetrapyridinoporphyrazine is extensively aggregated in the bacteria and fails to produce any detectable singlet oxygen. Full article
(This article belongs to the Special Issue New Trends in Photochemistry)
Open AccessArticle Diastereoselective [2+2] Photocycloaddition of Chiral Cyclic Enones with Olefins in Aqueous Media Using Surfactants
Molecules 2013, 18(2), 1626-1637; doi:10.3390/molecules18021626
Received: 7 January 2013 / Revised: 15 January 2013 / Accepted: 21 January 2013 / Published: 28 January 2013
Cited by 6 | PDF Full-text (269 KB)
Abstract
We conducted diastereodifferentiating [2+2] photocycloadditions of cyclo-hexenones modified with a chiral 8-(p-methoxy phenyl)menthyl auxiliary with olefins in water. Although the photoreaction didn’t proceed at all in pure water owing to very low solubility, the use of surfactants [sodium dodecyl sulfate (SDS)
[...] Read more.
We conducted diastereodifferentiating [2+2] photocycloadditions of cyclo-hexenones modified with a chiral 8-(p-methoxy phenyl)menthyl auxiliary with olefins in water. Although the photoreaction didn’t proceed at all in pure water owing to very low solubility, the use of surfactants [sodium dodecyl sulfate (SDS) or dodecylamine hydrochloride (DAH)] and additive (organic solvent) enabled the reactions to progress with moderate to high conversions and yields. Furthermore, we synthesized a new menthol derivative substrate containing a (p-octyloxy)phenyl group for enhancing hydrophobicity, and elucidated that this new substrate was found to be a suitable chiral auxiliary in this asymmetric photoreaction in aqueous system. The additive effect of organic molecules on the yield and diastereoselectivity of the photo-adducts is also discussed. Full article
(This article belongs to the Special Issue New Trends in Photochemistry)
Figures

Open AccessArticle Photochemical Synthesis and Properties of 1,6- and 1,8-Naphthalenophanes
Molecules 2013, 18(1), 1314-1324; doi:10.3390/molecules18011314
Received: 20 December 2012 / Revised: 9 January 2013 / Accepted: 15 January 2013 / Published: 21 January 2013
Cited by 4 | PDF Full-text (302 KB)
Abstract
Various 1,6- and 1,8-naphthalenophanes were synthesized by using the Photo-Dehydro-Diels-Alder (PDDA) reaction of bis-ynones. These compounds are easily accessible from w-(3-iodophenyl)carboxylic acids in three steps. The obtained naphthalenophanes are axially chiral and the activation barrier for the atropisomerization could be determined in some
[...] Read more.
Various 1,6- and 1,8-naphthalenophanes were synthesized by using the Photo-Dehydro-Diels-Alder (PDDA) reaction of bis-ynones. These compounds are easily accessible from w-(3-iodophenyl)carboxylic acids in three steps. The obtained naphthalenophanes are axially chiral and the activation barrier for the atropisomerization could be determined in some cases by means of dynamic NMR (DNMR) and/or dynamic HPLC (DHPLC) experiments. Full article
(This article belongs to the Special Issue New Trends in Photochemistry)

Review

Jump to: Research

Open AccessReview Potential Energy Surfaces and Quantum Yields for Photochromic Diarylethene Reactions
Molecules 2013, 18(5), 5091-5103; doi:10.3390/molecules18055091
Received: 5 February 2013 / Revised: 18 April 2013 / Accepted: 19 April 2013 / Published: 2 May 2013
Cited by 12 | PDF Full-text (499 KB) | HTML Full-text | XML Full-text
Abstract
Photochromic diarylethenes (DAEs) are among the most promising molecular switching systems for future molecular electronics. Numerous derivatives have been synthesized recently, and experimental quantum yields (QYs) have been reported for two categories of them. Although the QY is one of the most important
[...] Read more.
Photochromic diarylethenes (DAEs) are among the most promising molecular switching systems for future molecular electronics. Numerous derivatives have been synthesized recently, and experimental quantum yields (QYs) have been reported for two categories of them. Although the QY is one of the most important properties in various applications, it is also the most difficult property to predict before a molecule is actually synthesized. We have previously reported preliminary theoretical studies on what determines the QYs in both categories of DAE derivatives. Here, reflecting theoretical analyses of potential energy surfaces and recent experimental results, a rational explanation of the general guiding principle for QY design is presented for future molecular design. Full article
(This article belongs to the Special Issue New Trends in Photochemistry)
Open AccessReview Coordination Programming of Photofunctional Molecules
Molecules 2013, 18(4), 4091-4119; doi:10.3390/molecules18044091
Received: 23 January 2013 / Revised: 15 March 2013 / Accepted: 27 March 2013 / Published: 5 April 2013
Cited by 13 | PDF Full-text (1893 KB) | HTML Full-text | XML Full-text
Abstract
Our recent achievements relating to photofunctional molecules are addressed. Section 1 discloses a new concept of photoisomerization. Pyridylpyrimidine-copper complexes undergo a ring inversion that can be modulated by the redox state of the copper center. In combination with an intermolecular photoelectron transfer (PET)
[...] Read more.
Our recent achievements relating to photofunctional molecules are addressed. Section 1 discloses a new concept of photoisomerization. Pyridylpyrimidine-copper complexes undergo a ring inversion that can be modulated by the redox state of the copper center. In combination with an intermolecular photoelectron transfer (PET) initiated by the metal-to-ligand charge transfer (MLCT) transition of the Cu(I) state, we realize photonic regulation of the ring inversion. Section 2 reports on the first examples of heteroleptic bis(dipyrrinato)zinc(II) complexes. Conventional homoleptic bis(dipyrrinato)zinc(II) complexes suffered from low fluorescence quantum yields, whereas the heteroleptic ones feature bright fluorescence even in polar solvents. Section 3 describes our new findings on Pechmann dye, which was first synthesized in 1882. New synthetic procedures for Pechmann dye using dimethyl bis(arylethynyl)fumarate as a starting material gives rise to its new structural isomer. We also demonstrate potentiality of a donor-acceptor-donor type of Pechmann dye in organic electronics. Full article
(This article belongs to the Special Issue New Trends in Photochemistry)
Open AccessReview Photo-Induced Cycloaddition Reactions of α-Diketones and Transformations of the Photocycloadducts
Molecules 2013, 18(3), 2942-2966; doi:10.3390/molecules18032942
Received: 28 December 2012 / Revised: 5 February 2013 / Accepted: 6 February 2013 / Published: 4 March 2013
Cited by 5 | PDF Full-text (682 KB) | HTML Full-text | XML Full-text
Abstract
Photocycloaddition, along with subsequent transformation of the photocycloadducts, provides expeditious ways to construct various structures. The photo-induced reactions of α-diketones have been reported to proceed via different reaction pathways with the involvement of one or two of the carbonyl groups. Photoinduced reactions
[...] Read more.
Photocycloaddition, along with subsequent transformation of the photocycloadducts, provides expeditious ways to construct various structures. The photo-induced reactions of α-diketones have been reported to proceed via different reaction pathways with the involvement of one or two of the carbonyl groups. Photoinduced reactions of cyclic α-diketones including N-acetylisatin, phenanthrenequinone and isoquinolinetrione with different C=C containing compounds could take place via [2 + 2], [4 + 2] or [4 + 4] photocycloaddition pathways. We have investigated the photoreactions of these cyclic α-diketones with different types of alkenes and alkynes, with a focus on the unusual cascade reactions initiated by the photocycloaddition reactions of these cyclic α-diketones and the applications of these photocycloaddition reactions along with the transformation of the photocycloadducts. In this paper, we discuss the diverse photo-cycloaddition pathways found in the photocycloaddition of o-diones leading to various photocycloadducts and the potential applications of these reactions via further transformation reactions of the adducts. Full article
(This article belongs to the Special Issue New Trends in Photochemistry)

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