A quantum mechanical approach to electrochemical behavior of spirochromics

Fully optimized semiempirical quantum-chemical calculations of photochromic spiropyrans are presented. The vertical ionization potentials are calculat ed and their variation with substitutions are correlated to experimental ox idation potentials. The effects of the substitutions are studied and the pa rtial charges on indoline and pyran components generated by HOMO are found to be responsible for the variations. The deactivating groups on the indoli ne ring system and deactivating groups on the pyran system increase the ion ization potential and, consecutively, the oxidation potential. (C) 1999 Joh n Wiley & Sons, Inc.