Synthesis and photostability of functional squarylium dyes

Various symmetrical and unsymmetrical squarylium dyes have been synthesized and characterized with the aid of IR spectroscopy and solvatochromism. The photofading of squarylium dyes has been investigated in solution and in polyvinylbutyral (PVB) film with carbon are Fade-Ometer. The photostability of squarylium dyes increases with the electron-withdrawing power of substituent groups at the indoline moiety, The rates of photofading of these dyes were remarkably suppressed in the presence of hydroxycarboxylic acid metal salt, while the addition of UV-absorber afforded little retardation of the rate of fading. (C) 1997 Elsevier Science Ltd.