Solvatochromic and photochromic characteristics of new 1,3-dihydrospiro[2H-indole-2,2′-[2H]-bipyrido[3,2-f][2,3-h][1,4]benzoxazines]

Abstract

The mono-oxime of 1,10-phenanthroline-5,6-quinone reacts with 1,3,3-trimethyl-2-methyleneindoline, derivatives to give the corresponding spirooxazines, i.e. 1,3-dihydrospiro[2H-indole-2,2′-[2H]-bipyrido[3,2-f][2,3-h][1,4]benzoxazines]. These compounds exhibit particular solvatochromic behaviour, strongly dependent on the substitution pattern. At room temperature and without any light excitation, an equilibrium is established between closed and opened forms. The photochromic characteristics have been determined using flash photolysis coupled to a fast scanning spectrometer allowing the determination of rate constants for thermal bleaching, visible absorption and photocoloration. The coloured opened forms, either photoinduced or arising from the solvation effect, appear to be spectroscopically identical. Structural parameters of the short-lived photomerocyanines have also been obtained.