Peculiarities of photochromic behaviour of spiropyrans and spirooxazines

A comparative analysis of the spectral and photochromic properties of nitrosubstituted indolinic spirobenzopyrans (SBPs) and spironaphthooxazines (SNOs) is presented. Formation of the same trans isomer of the SNO coloured form at any temperature over a wide range (77-300 K) is proposed contrary to the case of SEP for which the photoproduct structure depends on temperature. Such photochromic parameters as the quantum yields of photocolouration and spirobond C-O dissociation, and the efficiency of photoinduced form stabilization are examined for nitrosubstituted SBPs and SNOs. (C) 1997 Elsevier Science S.A.