SYNTHESIS AND CHARACTERIZATION OF UNSYMMETRICAL BIS-INDOLINOSPIROBENZOPYRANS, A NEW CLASS OF THERMOCHROMIC AND PHOTOCHROMIC DYES

A new class of unsymmetrical bis-indolinobenzospiropyran dyes (U-BSP) and their precursors have been synthesized Unsymmetrical bis-indolinob enzospiropyrans are obtained by condensation of the precursor; Fischer base-spiropyran derivatives (FB-SPx), with substituted salicylaldehyd es. The alternative Fischer base-spiropyran precursor (FB-SPy), which has an electron-withdrawing substituent, was not found to be suitable for the synthesis of U-BSPs. The synthesized U-BSPs have been characte rized by H-1 NMR, UV-Vis, and mass spectroscopy; they show abnormal so lvatokinetic behavior in nonpolar solvents, suggestive of aggregate fo rmation.