Properties of unsymmetrical squarylium dyes containing strongly electron-donating 4′-amino-2,2′-bis(diethylamino)-4,5′-bithiazole residue

Abstract Novel unsymmetrical squarylium dyes containing the strongly electron-donating 4′-amino-2,2′-bis(diethylamino)-4,5′-bithiazole moiety were fluorescent and showed emission maxima around 640 nm. They have both alternant and intramolecular charge-transfer chromophoric systems.