PECULIARITIES OF PHOTOCHROMIC BEHAVIOR OF SPIROPYRANS AND SPIROOXAZINES

A comparative analysis of the spectral and photochromic properties of nitrosubstituted indolinic spirobenzopyrans (SBPs) and spironaphthooxa zines (SNOs) is presented. Formation of the same trans isomer of the S NO coloured form at any temperature over a wide range (77-300 K) is pr oposed contrary to the case of SEP for which the photoproduct structur e depends on temperature. Such photochromic parameters as the quantum yields of photocolouration and spirobond C-O dissociation, and the eff iciency of photoinduced form stabilization are examined for nitrosubst ituted SBPs and SNOs. (C) 1997 Elsevier Science S.A.