Synthesis and Photophysical Studies of 2-(Thiophen-2-yl)-4-(morpholin-4-yl) quinazoline Derivatives

The synthesis of a series of push-pull aryl and arylethynyl 2-(thiophen-2-yl) quinazoline derivatives is presented. The photophysical properties of the newly generated compounds are also described. Functionalization of the (2-thienyl) quinazoline fluorophore at the 5'-position with aryl and arylethynyl moieties was performed using bromination and subsequent palladium-catalyzed cross-coupling reactions. Optical studies revealed that 4-(diethylamino) phenyl and 4-(diphen-ylamino) phenyl derivatives emit green light upon irradiation, whereas their 4-(9H-carbazol-9-yl) phenyl, methoxyphenyl, thienyl and arylethynyl counterparts are characterized by blue light emission capabilities. The effect of protonation has also been studied, and the ability of some of these molecules to function as colorimetric and luminescent pH sensors has been demonstrated with significant color changes and luminescence switching upon the introduction of acid.