Photodimerization Of Anthracenes Research Articles

Template-Controlled Supramolecular Photodimerization of 2-Substituted Anthracenes Mediated by Metal–NHC Complexes

The photochemical cycloaddition reaction has been extensively investigated for many years due to its efficient accessibility for intriguing photochemical products. Nevertheless, such a photoreaction is still an ongoing challenge to control regio- and stereoselectivity during the reaction process. Herein, a series of mononuclear M(I)–NHC (M = metal, NHC = N-heterocyclic carbene) complexes [M(1)2](PF6) (M = Ag, Au; 1 = 1a–c) were designed and synthesized from 2-substituted anthracene derivatives H-1(PF6) (1 = 1a–c) and characterized by nuclear magnetic resonance (NMR) spectroscopy, electrospray ionization-mass spectrometry (ESI-MS), and single-crystal X-ray diffraction analyses. Upon irradiation at 365 nm, the [4 + 4] photodimerization of complexes [M(1)2](PF6) (M = Ag, Au; 1 = 1a–c) successfully proceeded with 100% conversion and gave the syn-head-to-head (HH) photodimers syn-HH-[M(2)](PF6) (M = Ag, Au) as major products. Based on M(I)–NHC templates, syn-HH-[Au(2)](PF6) (2 = 2a–c) was generated in 87–92% relative yields and syn-HH-[Ag(2)](PF6) (2 = 2a–c) in 65–70% relative yields as determined by 1H NMR spectra. This phenomenon revealed the efficient supramolecular control of the M(I)–NHC templates on the regio- and stereoselectivity of the [4 + 4] photodimerization in solution, which can be applied to a series of photoreactions in a controllable manner.

ChemInform Abstract: Substituent Effect in the Photodimerization of Amphiphilic Anthracenes: Reaction in Monolayer Assemblies and in Solutions.

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

ChemInform Abstract: Photodimerization of Anthracenes in the Solid State: New Insights on Application of Atomic Force Microscopy.

ChemInform Abstract: Photodimerization of Anthracenes in the Solid State: New Insights on Application of Atomic Force Microscopy.

ChemInform Abstract: Photodimerization of Anthracenes in Fluid Solutions. Part 2. Mechanistic Aspects of the Photocycloaddition and of the Photochemical and Thermal Cleavage

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

Photodimerization of anthracenes in fluid solutions: (part 2) mechanistic aspects of the photocycloaddition and of the photochemical and thermal cleavage

One of the classics in photochemistry, the photodimerization of anthracenes can be considered as a paradigm of the photocycloaddition of non saturated hydrocarbons. The historical steps of the mechanistic studies are reviewed: based on fluorescence quenching, cyclization quantum yields measurement, the influence of dioxygen and solvents, they support a singlet state pathway; the dimerization rate constants are found to be generally high for reactions occurring within a few nanoseconds unless they are slowed down or inhibited by steric strain. In several cases, excimers have been demonstrated to be intermediates and it is shown that excimer fluorescence and cyclization are competitive processes. Another intermediate known as pericyclic minimum (or conical intersection) is postulated to form a sort of floppy cycloadduct where the reacting centres are at mutual distances shorter than in excimers and longer than in dimers. For intermolecular dimerizations, the triplet state is also reactive but through triplet–triplet annihilation in dilute solutions. Intramolecular photocycloadditions have also been carefully examined, for the role of multiple excimer formation, regioselectivity (9,10∶1′,4′ and 9,10∶1′,2′ cyclization) and solvent polarity. The triplet state reactivity is shown to lead to 4π + 2π or 4π + 4π cycloadducts, depending on geometric factors. In the latter case when intersystem crossing is favoured by the substituents, cyclization quantum yields as high as 0.65–0.72 have been observed. Photodissociation quantum yields are generally high and the reactions are partly adiabatic, leading to excimer and monomer fluorescence, but the major part follows another pathway not fully elucidated by flash photolysis. Thermodynamic and kinetic parameters for the thermal cleavage are given; they reveal a large gamut of stability for the photocycloadducts.

Photodimerization of anthracenes in fluid solution: structural aspects

Owing to their versatile photophysical and photochemical properties, anthracene and its derivatives are being employed in many systems, for instance as energy migration probes in polymers, triplet sensitizers, molecular fluorosensors, electron acceptor or donor chromophores in artificial photosynthesis, photochromic substrates in 3D memory materials, etc. One remarkable feature is their ability to photodimerize under UV irradiation which induces considerable changes in their physical properties. This account reports the preparative and structural aspects of this very useful and protean photocycloaddition.

Phase behavior and photocrosslinking kinetics ofsemi-interpenetrating polymer networks prepared from miscible polymer blends

Mixtures of polystyrene derivatives (PSCS) and poly(vinyl methyl ether) (PVME) were made photocrosslinkable by chemically labeling PSCS chains with photoreactive anthracene. Miscibility of these anthracene-labeled PSCS/PVME blends was examined by light scattering under several crosslinking conditions in the one-phase region via photodimerization of anthracenes. As the reaction proceeds, the coexistence curve of PSCS/PVME blends shifts toward the low temperature side. By following the changes in concentration of anthracenes with irradiation time, it was found that the crosslinking reaction of PSCS chains in the blends does not follow the mean-field kinetics. However, it can be well expressed by the Kohlrausch–Williams–Watts (KWW) relaxation mechanism, indicating that the crosslinking reaction proceeds inhomogeneously in the blends. By scaling the reaction time with the average reaction rate obtained from the KWW equation modified for the reaction kinetics, all the crosslinking data obtained in the miscible region of the reacted blends fall on a single master curve. These experimental results suggest the universal behavior of the photocrosslinking kinetics obtained under the “shallow quench” conditions in the region far away from the coexistence curve of the reacting blends. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 455–462, 1998

Phase behavior and photocrosslinking kinetics of semi‐interpenetrating polymer networks prepared from miscible polymer blends

Mixtures of polystyrene derivatives (PSCS) and poly(vinyl methyl ether) (PVME) were made photocrosslinkable by chemically labeling PSCS chains with photoreactive anthracene. Miscibility of these anthracene-labeled PSCS/PVME blends was examined by light scattering under several crosslinking conditions in the one-phase region via photodimerization of anthracenes. As the reaction proceeds, the coexistence curve of PSCS/PVME blends shifts toward the low temperature side. By following the changes in concentration of anthracenes with irradiation time, it was found that the crosslinking reaction of PSCS chains in the blends does not follow the mean-field kinetics. However, it can be well expressed by the Kohlrausch–Williams–Watts (KWW) relaxation mechanism, indicating that the crosslinking reaction proceeds inhomogeneously in the blends. By scaling the reaction time with the average reaction rate obtained from the KWW equation modified for the reaction kinetics, all the crosslinking data obtained in the miscible region of the reacted blends fall on a single master curve. These experimental results suggest the universal behavior of the photocrosslinking kinetics obtained under the “shallow quench” conditions in the region far away from the coexistence curve of the reacting blends. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 455–462, 1998

Solid-State Photodimerization of Anthracenes Having a Chiral Substituent

Abstract Anthracenes containing a chiral substituent at the 9-position, AnCH(OAc)R (An = 9-anthryl; R = Me, Et, i-Pr, t-Bu, CF3), dimerized on UV irradiation in benzene to give two head-to-tail dimers, meso- and dl- forms with 1:1 ratio. In the solid state, some (R˭Et, i-Pr) gave one dimer exclusively, while in another case (R˭Me) dimerization proceeded slowly to give both dimers. The solid-state photochemical behavior can be explained based on the crystal structure.

Structure-Property Relationship of Polymer Blends with Co-Continuous Structures Prepared by Photo-Crosslinking

Polymer blends with co-continuous structures in the micrometer scale were obtained by photo-cross-linking of poly(2-chlorostyrene)/poly(vinyl methyl ether)(P2CS/PVME) mixtures undergoing the spinodal decomposition process. The reaction was carried out with UV light at 365 nm to induce the photodimerization of anthracenes labeled on the P2CS chains (P2CS-A). To obtain the blends with co-continuous structures of varying length scales (λ), P2CS-A/PVME blends having the same cross-link density were prepared by irradiation and subsequently annealed over different time intervals. The resulting morphology was observed by using phase-contrast optical microscopy and was analyzed by digital image analysis. It was found that the time evolution of these co-continuous structures follows the power law λ ∞ t α , where α is close to 1/4. This value is smaller than 1/3, as predicted by the Lifshitz-Slyozov-Wagner law, indicating that the spinodal decomposition was slowed down by the presence of cross-links. The physical properties of these photo-cross-linked blends were examined by dynamic mechanical measurements. For the same cross-link density, the storage modulus E' of P2CS/PVME blends increases with λ, whereas the loss peaks of these co-continuous structures shift to the high temperature side. These experimental results suggest that the combination of photo-cross-linking reactions and the phase separation kinetics of polymer blends has the potential of providing a new way to design multiphase polymer materials with controllable co-continuous structures in the micrometer range.

Photodimerization of Anthracenes in the Solid State: New Results from Atomic Force Microscopy

The phase changes for topochemically allowed and forbidden photodimerizations of crystalline anthracene derivatives [Eq. (a)] become visible under the atomic force microscope. In all cases, surprisingly, the formation of surfaces resembling ice floes is observed, accompanied by considerable material transport. No processes with minimal atomic and molecular movement are seen. The new phase formation must therefore be included in the reaction description from the beginning. R = H, CH3, Cl, CN.

ELECTRONIC ABSORPTION PROPERTIES OF SYMMETRICAL DIALKOXYANTHRACENES. LINEAR DICHROISM AND MAGNETIC CIRCULAR DICHROISM*

Abstract— Linear dichroism (LD) and magnetic circular dichroism (MCD) of symmetrical dialkoxy‐anthracenes and some related compounds were recorded in an attempt to elucidate electronic absorption properties and assign the nature of the lowest singlet excited state, recognized to control both the fluorescence and the photodimerization of anthracenes. The spectroscopic measurements proved that the lowest electronic transition is of the 1La type in all the compounds. The peculiar photoreactivity pattern is therefore governed by factors other than an inversion of the order of the 1La and 1Lb states and may be related to electronic density repartition on the different positions of the anthracene nucleus dictated by the position of the electron‐donating substituents.

Substituent effect in the photodimerization of amphiphilic anthracenes: reactions in monolayer assemblies and in solutions

The rate of intermolecular photodimerization of amphiphilic anthracenes was largely affected by the substitution to anthracene nucleus, both in monolayer assemblies and in MeOH solutions. A larger substituent effect was observed in monolayer assemblies compared with those in solutions.

ChemInform Abstract: Dissymmetrical Photodimerization of Anthracenes: A New Example Related to the Conformation Properties of the Silicon Hinge Linking the Two Chromophores.

ChemInformVolume 20, Issue 37 Preparative Organic Chemistry ChemInform Abstract: Dissymmetrical Photodimerization of Anthracenes: A New Example Related to the Conformation Properties of the Silicon Hinge Linking the Two Chromophores. J.-P. DESVERGNE, J.-P. DESVERGNE Lab. Photochim. Org., CNRS, Univ. Bordeaux I, 33405 Talence, Fr.Search for more papers by this authorN. BITIT, N. BITIT Lab. Photochim. Org., CNRS, Univ. Bordeaux I, 33405 Talence, Fr.Search for more papers by this authorJ.-P. PILLOT, J.-P. PILLOT Lab. Photochim. Org., CNRS, Univ. Bordeaux I, 33405 Talence, Fr.Search for more papers by this authorH. BOUAS-LAURENT, H. BOUAS-LAURENT Lab. Photochim. Org., CNRS, Univ. Bordeaux I, 33405 Talence, Fr.Search for more papers by this author J.-P. DESVERGNE, J.-P. DESVERGNE Lab. Photochim. Org., CNRS, Univ. Bordeaux I, 33405 Talence, Fr.Search for more papers by this authorN. BITIT, N. BITIT Lab. Photochim. Org., CNRS, Univ. Bordeaux I, 33405 Talence, Fr.Search for more papers by this authorJ.-P. PILLOT, J.-P. PILLOT Lab. Photochim. Org., CNRS, Univ. Bordeaux I, 33405 Talence, Fr.Search for more papers by this authorH. BOUAS-LAURENT, H. BOUAS-LAURENT Lab. Photochim. Org., CNRS, Univ. Bordeaux I, 33405 Talence, Fr.Search for more papers by this author First published: September 12, 1989 https://doi.org/10.1002/chin.198937097Read the full textAboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinked InRedditWechat No abstract is available for this article. Volume20, Issue37September 12, 1989 RelatedInformation

Acceleration of the photodimerization of water-soluble anthracenes included by ?- and ?-cyclodextrins

Acceleration of the photodimerization of water-soluble anthracenes included by ?- and ?-cyclodextrins

Determination of the absolute quantum efficiency of the luminescence of crystalline anthracene and of meso–dimeso derivatives using photoacoustic spectroscopy

In this study, photoacoustic spectroscopy (p.a.s.) has been employed as a calorimetric method for the determination of the luminescent quantum efficiency (ηF) of several solid materials: 1,4-bis(4-methyl-5-phenyloxazol-2-yl)benzene, anthracene and eleven meso and dimeso anthracene derivatives. The technique used utilizes the phenomenon of photoacoustic saturation, in which the amplitude of the p.a. signal is independent of the absorption coefficient of the samples. Fluorescence quantum efficiency values of some anthracenes have also been determined using fluorescence measurements relative to pyrene crystals and they are shown to give results consistent with p.a. values. These data have been interpreted to estimate the relative rates of photodimerization of meso anthracenes in their crystal forms, and evidence for the existence of the 9-phenylanthracene crystal dimer is found in the p.a. spectra.

New intramolecular exciplexes between polynuclear aromatic hydrocarbons and head-to-head vs head-to-tail photodimerization of mesosubstituted anthracenes.

New dissymetrical non conjugated bichromophores linked by an oxygenated chain: (9-anthrylmethyloxymethyl)arenes[arenes:benzene(I a),2-naphthalene(I b),9-phenanthrene (I c) and 1-pyrene (I d) and (9-phenanthrylmethyloxymethyl)-1-pyrene (II)] have been prepared. I c–d and II exhibit intramolecular exciplex fluorescence in methylcyclohexane at room temperature. Intramolecular photoadducts were not found but I a–d yield a mixture of head-to-head and head-to-tail anthracenic photodimers.

From anthracene photodimerization to jaw photochromic materials and photocrowns

The inter and intramolecular photochemical reactions of anthracenes in the absence of oxygen is discussed. The intermolecular photodimerization of 9-substituted anthracenes in fluid solution usually leads to head-to-tail photodimers; it will be shown that this trend can be obviated by non bonding attractive interactions between substituents or by mixed photodimerization. The mechanistic aspects will be examined, next, in connection with the problem of excimer intermediacy. Bis-9-anthracenes can form photocyclomers and, in certain cases, intramolecular excimers at room temperature. Those which display interesting photochromic properties, were called jaw compounds; some of them induce an unusual anthracene ring cyclomerization. A study of photophysical and photochemical processes by steady state and transient kinetic analysis of ,c)-bis-9-anthryl-n-alkanes (ethane to decane) and cC ,C) -bis-9-anthryl-polyoxaalkanes allows a deeper insight into the mechanism of photodimerization. By irradiation, the latter derivatives can generate photocrowns; this is the first photochemical synthesis of crown-ethers.