Photoisomerization Of Stilbene Research Articles

Ab Initio Study of Cis−Trans Photoisomerization in Stilbene and Ethylene

The photochemistry of stilbene is investigated using ab initio quantum chemistry with complete active space self-consistent field (CASSCF) and multireference perturbation theory (CASPT2) methods. We characterize photoisomerization pathways from both the cis and trans isomers, including a minimal energy conical intersection. Similarities to photoisomerization in ethylene are found and emphasized. In contrast to traditional one-dimensional models of stilbene photoisomerization, torsion and pyramidalization are required to reach the minimal energy conical intersection which is expected to dominate in quenching to the ground electronic state. This intersection is characterized as an interaction between charge transfer and covalent states. The present results suggest that the qualitative features of the photoisomerization dynamics elucidated for ethylene can also be expected to apply to stilbene, and call for reconsideration and refinement of the photoisomerization mechanism in stilbene.

A rotaxane synthesis based on stilbene photoisomerization. A photoswitchable catch and release process.

A [2]rotaxane, having (Z)-alpha-methylstilbene as a stopper, is (1) synthesized in good yield by using a (E)- to (Z)-stilbene photoisomerization process, and (2) dissociated by reverse photoisomerization from (Z)- to (E)-stilbene.

Direct and sensitized (energy and electron transfer) geometric isomerization of stilbene within zeolites: a comparison between solution and zeolite as reaction media

The trans- and cis-stilbenes upon inclusion in NaY zeolite are thermally stable. Direct excitation and triplet sensitization results in geometric isomerization and the excited state behavior under these conditions are similar to that in solution. Upon direct excitation, a photostationary state consisting of 65% cis and 35% trans isomers is established. Triplet sensitization with 2-acetonaphthone gave a photostationary state consisting of 63% cis and 37% trans isomers. These numbers are similar to the ones obtained in solution. Thus, the presence of cations and the confined space within the zeolite have very little influence on the overall chemistry during direct and triplet sensitization. However, upon electron transfer sensitization with N-methylacridinium (NMA) as the sensitizer within NaY, isomerization from cis-stilbene radical cation to trans-stilbene occurs and the recombination of radical ions results in triplet stilbene. Prolonged irradiation gave a photostationary state (65% cis and 35% trans) similar to triplet sensitization. This behavior is unique to the zeolite and does not take place in solution. Steady state fluorescence measurements showed that the majority of stilbene molecules are close to the N-methylacridinium sensitizer. Diffuse reflectance flash photolysis studies established that independent of the isomer being sensitized only trans radical cation is formed. Triplet stilbene is believed to be generated via recombination of stilbene radical cation and sensitizer radical anion. One should be careful in using acidic HY zeolite as a medium for photoisomerization of stilbenes. In our hands, in these acidic zeolites isomerization dominated the photoisomerization.

Viscosity dependence and solvent effects in the photoisomerization of cis-stilbene: Insight from a molecular dynamics study with an ab initio potential-energy function

Molecular-dynamics simulations of the photoisomerization of cis-stilbene in supercritical argon were performed. The stilbene molecule is represented by ab initio quantum chemistry, while the solvent, the interaction with solvent, and the time evolution were described by classical mechanics. Reaction rate constants are estimated and their dependence on temperature, pressure, and viscosity are investigated. Agreement with available experimental data was obtained. Our simulations strongly suggest a minimum on the excited-state potential-energy surface at a gauche conformation which is very rapidly reached after excitation, which leads to nonequilibrium barrier transitions. Specific solvent effects were identified. Implications on the current opinion on stilbene photoisomerization are discussed.

Mechanism and Potential Energy Surface for Photoisomerization of Stilbene in Zeolite Nanospace

The photoisomerization of cis- and trans-stilbenes adsorbed in zeolite supercage was studied by means of Raman spectroscopy for in situ analysis of the isomer ratio in the photostationary state. It was found that the isomerization proceeds mainly through the singlet excited states for NaY and triplet excited states for KY, and also a new potential energy surface for the photoisomerization was proposed.

Quantum energy flow during molecular isomerization

Intramolecular energy flow greatly influences molecular isomerizations, particularly when the energy barrier to reaction is low, as in catalytic and biochemical reactions. We discuss here a simple quantum mechanical theory that describes the extent and rate of vibrational energy flow in molecules, and apply it for the first time to predict rates of isomerization. We consider trans-cis photoisomerization of stilbene, which has been extensively studied experimentally. Vibrational flow in stilbene plays a crucial role in moderating isomerization; the rate both in supersonic jets and low pressure gases is well described by the theory treating quantum flow.

Photochemistry in stilbene-containing monolayers. Part II: effect of cation binding on photoisomerization

A new stilbene-containing amphiphile with the chromophore in the hydrophilic headgroup was synthesized, and the photoisomerization of the stilbene sulfonate was investigated at the air-water interface. It could be shown that the isomerization leads to a decrease in area per molecule. The binding of inorganic and organic cations from the subphase occurs in the nanomolar concentration range. Binding was verified by UV and fluorescence spectroscopy and by electron spectroscopy for chemical analysis. Upon complexation with alkaline earth metals, the stilbene photoisomerization proceeds apparently faster, whereas organic cations of the viologen type quench the photoreaction. This is the first example of a control of photoisomerization in monolayers by cation complexation.

Command surfaces 14 [1]. Photoregulation of in-plane alignment of a liquid crystal by the photoisomerization of stilbenes chemisorbed on a substrate silica surface

Abstract Stilbenes were attached to a quartz surface at their 2-position by silylation through a spacer to determine the capability to regulate an azimuthal alignment of a nematic liquid crystal by irradiation with linearly polarized light. Liquid crystal molecules aligned perpendicular to the direction of polarization plane of the actinic light, just as in the case of surface azobenzenes. The efficiency of the photoregulation was influenced by excitation wavelength and hence related with an E/Z isomeric ratio in a photostationary state. The irradiation with 260 nm polarized light resulting in the E-isomer as a major component in the photostationary state gave better optical quality of a photoaligned texture when compared with 330 nm irradiation, suggesting that the orientation of liquid crystals is induced by the rod-like E-isomer. Discussion was made on the possibility of the role of phenanthrenes, which were formed upon prolonged irradiation, in the liquid crystal photoalignment.

Models for stilbene photoisomerization: experimental and theoretical studies of the excited-state dynamics of 1,2-diphenylcycloalkenes

The initial dynamics in the photoisomerization of cis-stilbene, especially the dynamics leading to photocyclization, is explored by studying the high-resolution spectroscopy and implied dynamics of a series of 1,2-diphenylcycloalkenes. These molecules are isochromophoric to cis-stilbene but are structurally hindered from undergoing cis-trans isomerization. In particular, the high-resolution fluorescence excitation spectrum of 1,2-diphenylcyclobutane (DPC-4) reveals detailed information about the symmetric in-plane bend and symmetric phenyl ring twist motions, which are crucial to photocyclization. The DPC-4 spectrum is analyzed theoretically, and an empirical surface is constructed for the S 1 state that reproduces both line positions and relative intensities in the observed spectrum. Evidence for the importance of photocyclization in the dynamics of excited state cis-stilbene is presented and discussed

Hindered photoisomerization of stilbene at the liquid-solid interface: An illustration of coupled adsorption-reaction problems for physisorbed molecules

The 1B 1u excited state lifetime of trans-stilbene adsorbed at the interface between liquid hexane and solid aluminum oxide has been studied using picosecond multiple light scattering techniques. A perturbation analysis of the two-flux model for transient light absorption and transient light scattering in a strongly scattering medium is presented. Application of the scattering method to stilbene isomerization shows that torsional decay at the interface is slower than in solution and is characterized by an increased activation barrier (4.7 kcal/mol) and a reduced pre-exponential factor (1.2×10 12 s −1). These results are interpreted using an equation of motion for the time evolution of reactants trapped at the interface by a noncovalent adsorption potential. According to this model the change in activation energy arises from different adsorption strengths for reactant and transition state molecular structures. The change in pre-exponential factor reflects different shapes and equilibrium positions for the reactant and transition state adsorption potential functions.

On the dimensionality of stilbene isomerization

Stilbene photoisomerization is a useful model system for the investigation of condensed phase reaction dynamics. This manuscript presents data on the photoisomerization of meta-methyl-substituted stilbenes in decane as a function of temperature. These kinetic data indicate that the torsional motion around the bond joining the phenyl ring to the ethylenic carbon occurs on time-scales similar to trans to cis photoisomerization. The results for this model system and previous spectroscopic results suggest that a one-dimensional reaction coordinate may not be appropriate in describing stilbene isomerization.

ChemInform Abstract: Structures of (E,E)-1,1′-Ethanediylidenebis(2,3-dihydro-1H-indene), (E,E)-1,1′-Ethanediylidenebis(1,2,3,4-tetrahydronaphthalene) and (E,E)-5,5′-Ethanediylidenebis(6,7,8,9-tetrahydro-5H-benzocycloheptene).

The title compounds (I) (all space group P21/c with Z=2) are prepared as part of a study on the photoisomerization of stilbene and diphenylbutadiene.

Photoisomerization of stilbene - a theoretical study of deuteration shifts and limited internal vibrational redistribution

Very detailed experimental studies of the isomerization of trans-stilbene in the S 1 excited electronic state show features which are not readily explained by current theory, e.g., of RRKM type. In this work the deuteration shifts seen in the series C 14H 12, C 14H 10D 2, C 14D 10H 2, C 14D 12, where in the middle two species the ethylenic bridge positions are listed last, are investi RRKM theory modified so as to allow for a finite energy transfer rate between a critical oscillator and the remaining modes of the molecule. Vibrational frequencies are estimated on the basis of experimental results for the ground state molecule with the help of a product rule for deuteration shifts.

ChemInform Abstract: Unimolecular Reactions in Isolated and Collisional Systems: Deuterium Isotope Effect in the Photoisomerization of Stilbene

ChemInformVolume 20, Issue 19 Preparative Organic Chemistry ChemInform Abstract: Unimolecular Reactions in Isolated and Collisional Systems: Deuterium Isotope Effect in the Photoisomerization of Stilbene S. H. COURTNEY, S. H. COURTNEY Dep. Chem., Univ. Chicago, Chicago, IL 60637, USASearch for more papers by this authorM. W. BALK, M. W. BALK Dep. Chem., Univ. Chicago, Chicago, IL 60637, USASearch for more papers by this authorL. A. PHILIPS, L. A. PHILIPS Dep. Chem., Univ. Chicago, Chicago, IL 60637, USASearch for more papers by this authorS. P. WEBB, S. P. WEBB Dep. Chem., Univ. Chicago, Chicago, IL 60637, USASearch for more papers by this authorD. YANG, D. YANG Dep. Chem., Univ. Chicago, Chicago, IL 60637, USASearch for more papers by this authorD. H. LEVY, D. H. LEVY Dep. Chem., Univ. Chicago, Chicago, IL 60637, USASearch for more papers by this authorG. R. FLEMING, G. R. FLEMING Dep. Chem., Univ. Chicago, Chicago, IL 60637, USASearch for more papers by this author S. H. COURTNEY, S. H. COURTNEY Dep. Chem., Univ. Chicago, Chicago, IL 60637, USASearch for more papers by this authorM. W. BALK, M. W. BALK Dep. Chem., Univ. Chicago, Chicago, IL 60637, USASearch for more papers by this authorL. A. PHILIPS, L. A. PHILIPS Dep. Chem., Univ. Chicago, Chicago, IL 60637, USASearch for more papers by this authorS. P. WEBB, S. P. WEBB Dep. Chem., Univ. Chicago, Chicago, IL 60637, USASearch for more papers by this authorD. YANG, D. YANG Dep. Chem., Univ. Chicago, Chicago, IL 60637, USASearch for more papers by this authorD. H. LEVY, D. H. LEVY Dep. Chem., Univ. Chicago, Chicago, IL 60637, USASearch for more papers by this authorG. R. FLEMING, G. R. FLEMING Dep. Chem., Univ. Chicago, Chicago, IL 60637, USASearch for more papers by this author First published: May 9, 1989 https://doi.org/10.1002/chin.198919107Read 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 onFacebookTwitterLinkedInRedditWechat No abstract is available for this article. Volume20, Issue19May 9, 1989 RelatedInformation

Unimolecular reactions in isolated and collisional systems: Deuterium isotope effect in the photoisomerization of stilbene

The isomerization of t-stilbene (stilbene h12 ) and three deuterated derivatives has been studied in a supersonic expansion, the thermal gas phase, and solution. In the jet we find that almost all effect of full deuteration (stilbene d12 ) is produced by deuteration of the two ethylinic hydrogens only (stilbene d2 ). Complete deuteration of the phenyl rings (stilbene d10 ) has rather little influence on the decay of the jet-cooled molecule. Nonexponential decays are found at intermediate excess energies in the jet-cooled system, with the degree of nonexponentiality decreasing with increasing excess energy. The ordering of the decay rates observed in the jet is not consistent with previous RRKM calculations of the isomerization rates of stilbene h12 and d2. Using similar parameters the calculations consistently place the stilbene d2 and stilbene d10 curves in the wrong order. Our results suggest extensive but not complete vibrational relaxation in the isolated molecule. Vibrational redistribution rapidly becomes complete in the presence of buffer gas. In thermal samples the isomerization rates of stilbene h12 and stilbene d10 are identical over a wide range of solvents and temperatures. By contrast the isomerization rates in stilbene d2 and stilbene d12 are 1.4 and 1.5 times slower than in stilbene h12. Again, these ratios appear constant over a wide range of experimental conditions.

1H CIDNP study of the role of radical ions in the cis-trans isomerization of stilbenes in the presence of electron donors and acceptors

The role of radical ions in the photoisomerization of stilbenes in the presence of triphenylamine, N,N,N′,N′-tetramethyl-1,4-phenylenediamine, p-chloranil, 9-cyanophenanthrene, 9-cyanoanthracene and decafluorobenzil has been studied. If radical anions of stilbenes or radial cations of trans-stilbene are formed in the reaction, isomerization takes place in the triplet-excited stilbene molecule. If radical cations of cis-stilbene are formed they self-isomerize.

Vibronic perturbations in the cis-trans photoisomerization of stilbene

The direct cis-trans photoisomerization of stilbene is the result of two internal conversions, S 1 ⇝ S 2 and S 2 ⇝ S 0 respectively. The vibronic perturbations inducing such processes are computed by a modified CNDO/S program. Several vibrations are found to contribute to the S 1–S 2 coupling, but only one, that based on a C eH out-of-plane motion, to the S 2-S 0 vibronic coupling. The relevance of these results for the properties of the photoisomerization is discussed.

Photoisomerization of stilbene in low viscosity solvents: Comparison of isolated and solvated molecules

The photoisomerization of stilbene has been studied in low viscosity liquid alkanes and in the gas phase. The barrier crossing process shows no evidence of a low-friction or energy controlled region even at the lowest liquid viscosities studied. We present evidence that the barrier crossing may be in the energy controlled region in the thermal vapor. We discuss the influence of intramolecular vibrational energy transfer on the observed dynamics and note that entropy effects should be considered in comparing experimental data with theoretical models.

ChemInform Abstract: Picosecond Dynamics am! Photoisomerization of Stilbene in Supersonic Beams. Part 1. Spectra and Mode Assignments. Part 2. Reaction Rates and Potential Energy Surface.

Chemischer InformationsdienstVolume 16, Issue 19 Preparative Organic Chemistry ChemInform Abstract: Picosecond Dynamics am! Photoisomerization of Stilbene in Supersonic Beams. Part 1. Spectra and Mode Assignments. Part 2. Reaction Rates and Potential Energy Surface. J. A. SYAGE, J. A. SYAGESearch for more papers by this authorP. M. FELKER, P. M. FELKERSearch for more papers by this authorA. H. ZEWAIL, A. H. ZEWAILSearch for more papers by this author J. A. SYAGE, J. A. SYAGESearch for more papers by this authorP. M. FELKER, P. M. FELKERSearch for more papers by this authorA. H. ZEWAIL, A. H. ZEWAILSearch for more papers by this author First published: May 14, 1985 https://doi.org/10.1002/chin.198519111AboutPDF 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. Volume16, Issue19May 14, 1985 RelatedInformation

Transient Raman studies of the cis—trans photoisomerization processes in stilbene and retinal

This article reviews the present status of the application of transient or time-resolved Raman spectroscopy to the mechanistic studies of the cis—trans photoisomerization in conjugated molecules. Attention is focused on the vibrational information about the molecular structure of the electronically excited intermediates which are involved in the process of photoisomerization. Two examples, the trans to cis photoisomerization of stilbene through the lower excited singlet state and the cist to trans isomerization of retinal through the lowest excited triplet state, are included.