AIE active quinazoline based probes for selective detection of Fe3+ and acidochromism

Abstract

Synthesis and thorough characterizations of two A-D-π-A’ type asymmetric donor–acceptor constructs 6-(4-(4-(pyridin-2-yl)piperazin-1-yl)-phenyl)-5,6-dihydrobenzo-[4,5]-imidazo[1,2–c]-quinazoline (P1) and 6-(4-(4-(pyrimidin-2-yl)-piperazin-1-yl)phenyl)-5,6-dihydro-benzo[4,5]-imidazo[1,2–c] quinazoline (P2) have been described. The formation and composition of these compounds have been ascertained by spectroscopic studies (IR, 1H, 13C, ESI–MS, UV/Vis and fluorescence). Quinazoline unit in P1 and P2 acts as acceptor whereas piperazine as donor moiety and their properties has further been tuned by incorporating pyridyl and pyrimidyl group. AIE behaviour of P1 and P2 have been studied in THF/water by absorption and emission spectroscopy by varrying water fraction. Prominent role of the restriction of intra-molecular rotation on (RIR) in AIE for these compounds has been supported by viscosity measurements. Photophysical behaviour and morphology of the aggregates have been investigated by UV/Vis, fluorescence, and scanning electron microscopy (SEM). Owing to asymmetric donor–acceptor (A-D- π -A’) nature these display (twisted intramolecular charge transfer) TICT via D-A unit. In addition, P1 and P2 serve as highly selective and sensitive fluorescence sensor for Fe3+ and Job’s plot analysis suggested 2:1 binding stoichiometry between the metal centre Fe3+ and probes. As well, P1 and P2 display promising reversible acidochromism.