Synthesis and properties of thermo- and photochromic bisindolinobenzospiropyrans linked by thio- and carbonyl groups

Novel thermo- and photochromic thio- and carbonylated bisspiropyrans have b een synthesized by the reaction of 5,5'-thiobissalicylaldehydes or the 5,5' -carbonyl analogue and Fischer's base derivatives in 1:2.5 mole ratios. For the synthesis of 5,5-thio- or carbonylbissalicylaldehyde, 4,4'-thiodipheno l or 4,4'-carbonylbisphenol was formylated with paraformaldehyde. The synth esized dyes were characterized using H-1 NMR, IR, UV-vis and mass spectrosc opy. The thio-bisspiropyrans showed no thermo- and photochromism whereas th e carbonylated dyes showed weak thermo- and photochromism. (C) 2001 Elsevie r Science Ltd. All rights reserved.