Simulation of cis-trans photoinduced transitions IB bis-Schiff base molecules

Quantum chemical and molecular dynamics simulations of photoinduced UV-absorption and circular dichroism of a new synthesized symmetrical-base derived from condensation of two mole 5-(4-diethylamino-phenyl)-penta-2,4-dienaI with a chiral diamine were performed. Photoinduced changes from trans- to cis-isomers in chromophore and transitions between the trans-trans and cis-cis isomers corresponding to right- and left-enantiomers through the metastable cis-trans conformation may explain the observed spectral measurements. The crucial role in the observed transitions is played by C=C bonds close to the benzyl planes of the bis-based molecules (bis-Schiff base, BSB). At the same time rotation of the benzoate rings (about 110degrees) seems to be important. The performed simulations show that among the calculational technique Adamo-Barone DFT method gave better agreement with experiment. (C) 2003 Elsevier B.V. All rights reserved.