Oelgemoeller, Michael, Brem, Bernhard, Frank, Rudolf, Schneider, Siegfried, Lenoir, Dieter, Hertkorn, Norbert, Origane, Yumi, Lemmen, Peter, Lex , Johann, and Inoue, Yoshihisa (2002) Cyclic trans-stilbenes: synthesis, structural and spectroscopic characterization, photophysical and photochemical properties. Journal of the Chemical Society, Perkin Transactions 2, 2002 (10). pp. 1760-1771.

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Abstract

trans-Stilbene and several cyclic derivatives with hindered free rotation around the C(vinyl)–C(phenyl) single bond were studied by various spectroscopic techniques. Those derivatives which contain 6- or 7-membered aliphatic rings do not exhibit any measurable S₁->S₀ fluorescence. The introduction of two methoxy groups into the 6-membered aliphatic ring derivative accelerates its photoreactivity to such an extent that fluorescence or resonance Raman spectroscopy investigations become impossible. The introduction of aliphatic rings has only a little effect on the frequency of the phenyl-ring stretching vibrations, but pronounced ones on the IR and Raman intensities. The frequency of the vinylic stretching mode is downshifted between 5 and 100 cm⁻¹ except in the case of the derivative with the 4-membered ring, which experiences a hypsochromic shift of 80 cm⁻¹. Only trans-stilbene and its 4-membered cyclic analogues were amenable to fluorescence lifetime measurements. Analysis of VT-NMR spectra of stilbene 7 reveals a barrier of 15.9 kcal mol⁻¹ for equilibration of aliphatic equatorial and axial H-atoms.

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