s‐cis octatetraene: Photoproduction and spectroscopic properties

Irradiation of solutions of all‐trans octatetraene in n‐octane and cyclohexane at temperatures below 10 K efficiently produces a photoproduct whose fluorescence and absorption spectra are shifted ∼1200 cm−1 to lower energy than the corresponding features in the all‐trans precursor. High resolution excitation and fluorescence spectra and fluorescence lifetimes for this product have been determined. These data establish that the photoproduct is a noncentrosymmetric octatetraene isomer. The spectroscopic properties and thermal lability of this isomer are consistently interpreted if it is assumed that the photoproduct is generated from all‐trans octatetraene by isomerization about one of the single bonds.

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