Stilbene.  A critical commentary and some new calculations on its structure and isomerization

“…Differently substituted stilbenes and a-cyanostilbenes have often been investigated because of their structural features [1] and biological activities [2 -4 ]. Literature data concerning the spectra of stilbene and (^-substituted stilbene-like structures do exist [5 -8], but we could not find results on their fluorescence in dependence of the a-substitution.…”

Section: Introductionmentioning

confidence: 99%

Media Effect upon the Fluorescence Ability of Differently Substituted α-Cyanostilbenes

Nikolov

Petkova

Stoyanov

2001

Zeitschrift Für Naturforschung A

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The steady state and dynamic photophysical characteristics of a-cyanostilbene derivatives have been investigated in solution and in Polyvinylchloride (PVC) film at 300 K as well as in a frozen matrix at 77 K. While no emission is observed in solution, a significant fluorescence ability is registered both in PVC and frozen media. This fact is attributed to the matrix effect, which lessens the possible intramolecular motions around the central double bond. No phosphorescence at 77 K is observed. The fluorescence lifetimes at 77 K are compared with literature data for similar chemically fixed structures.

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Density Functional Studies of the Ground- and Excited-State Potential-Energy Curves of Stilbenecis-trans Isomerization

et al. 2002

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Using spin‐unrestricted density functional theory (the VWN Becke–Perdew potential), including broken‐symmetry and spin‐projection methods, we have obtained the potential‐energy curves as a function of the central torsional angle of stilbene in the ground (S0), the first excited triplet (T1), the first excited singlet (S1), and the doubly excited singlet (S2) states. The thermal trans→cis isomerization of stilbene passes through a diradical broken‐symmetry electronic structure around the twisted conformation (90° central torsional angle) in the ground state. Our calculations support the proposed triplet mechanism for sensitized cis⇌trans photoisomerization and the nonadiabatic singlet mechanism proposed by Orlandi and Siebrand.1 On the T1 potential‐energy curve, the rotation of the C=C bond for both trans‐ and cis‐stilbene will lead stilbene to the twisted conformation, from which the twisted stilbene will decay to the ground‐state surface that is nearly isoenergetic with the T1 surface and has diradical electronic structure in the twisted region. On the S1 potential‐energy curve, the energy increases in the direction from trans‐ to the twisted stilbene, and crosses with the neutral doubly excited S2 potential‐energy curve, which has a minimum at the twisted structure and is lower in energy than the zwitterionic doubly excited state. The twisted stilbene around the energy minimum of the neutral doubly excited S2‐state will decay onto the ground‐state surface from where the rotation of the C=C bond leads the twisted stilbene to either the trans or cis configuration and the isomerization of stilbene is then completed. Similar studies have also been performed on a stilbene derivative with a substituent group, NHCOCH3.

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Stilbene. A critical commentary and some new calculations on its structure and isomerization

Cited by 21 publications

References 33 publications

Photoisomerization dynamics of stilbenes

Photoisomerization dynamics of stilbenes

Media Effect upon the Fluorescence Ability of Differently Substituted α-Cyanostilbenes

Density Functional Studies of the Ground- and Excited-State Potential-Energy Curves of Stilbenecis-trans Isomerization

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