A theoretical study of the photochromic mechanism of a novel photochromic compound: 1-phenyl-3-methyl-4-(4-bromobenzal) pyrazolone-5 thiosemicarbazone

摘要

Semi-empirical AM1 method and DFT method (B3LYP/6-31G*) are used to investigate the photochromic mechanism of 1-phenyl-3-methyl-4-(4-bromobenzal) pyrazolone-5 thiosemicarbazone. The title compound is photochromic and non-planar. Intermolecular hydrogen bonds are observed between the pairs of atoms O and N(5) [2.853(3) Angstrom], O and N(8) [2.957(4) Angstrom]. The H atom is essentially bonded to the N atom. The crystal structure of the title compound is optimized and characterized as the minima of the potential energy surface at AM I level and DFT (B3LYP/6-31G*) level, respectively. NBO charge distribution, conformation and HOMO and LUMO molecular orbitals are analyzed using the results calculated at B3LYP/6-31G* level. The results can well explain these experimental phenomena and indicate that the title compound's photochromic mechanism is the function of conformation, charge and orbital. The work is helpful to further study the photochromic intermolecular proton transfer mechanism. (C) 2004 Elsevier B.V. All rights reserved.