New insight into the photochromic mechanism of 1,3‐diphenyl‐4‐(4‐fluoro)benzal‐5‐pyrazolone N(4)‐phenyl semicarbazone

Abstract

Density functional theory (DFT) calculation has been carried out to investigate the photochromic mechanism of 1,3-diphenyl-4-(4-fluoro)benzal-5-pyrazolone N(4)-phenyl semicarbazone. The novel mechanism, proposed by us, has different reaction pathway between the forward and the reverse process. The energy barrier of the forward direction was calculated to be significantly larger than that of the reverse direction (30.35 kcal/mol to 9.88 kcal/mol), which confirms the experimental observation that the forward process needs irradiation of light while the reverse one will take place easily when heated. The solvent effect on the relative stabilities of those isomers that may involve in the reaction has also been investigated by applying the polarizable continuum model (PCM) of the self-consistent reaction field theory.