Effect of Acetonitrile Completely Suppressing Trans-to-cis Photoisomerization of Styrylpyrene Substituted with a Nitro Group

Abstract

Acetonitrile completely suppresses trans-to-cis isomerization of 1-[2(4-nitrophenyl)ethenyl]pyrene.

1‐(Arylalkenyl)pyrenes – Synthetic, Structural, Photophysical, Theoretical, and Electrochemical Investigations

“…Surprisingly the emission spectra do not bear a mirror image relationship to the absorption spectra, which was pointed out by Nakajima when he studied the absorption and emission spectra of pyrenes. [24] This loss of the mirror image relationship is analogous to the spectra published by Kikutchi et al [23] These spectra, as well as our spectra of 4d, 4e, 4f, and 4g, contain two bands at shorter wavelengths and two shoulders at longer wavelengths. Compared to the fluorescence spectra of pyrene, the spectra of the pyrenylstyrenes contain no fine structure.…”

“…The electron withdrawing groups of 4f and 4g do not cause such a broadening. This shift to longer wavelengths due to electron withdrawing groups is already known from trans-stilbene, [21] styrylpyrenes, [23] and arylethynylpyrenes.…”

“…Yang et al gave an explanation based on intramolecular charge transfer due to the effect of the electron donating or accepting substituent to the molecule. [23] In other words, the electronic ambience is responsible for the loss of the fine structure. Strong electron donating or withdrawing groups should cause a greater loss of fine structure than weaker groups.…”