Design and synthesis of fluorescent 6-aryl[1,2-c]quinazolines serving as selective and sensitive ‘on-off’ chemosensor for Hg2+ in aqueous media

Three fluorescent quinazolines thiophen-2-yl-5,6-dihydrobenzo-[4,5]imidazo[1,2-c]quinazoline (1), pyridin-3-yl-5,6-dihydrobenzo-[4,5]imidazo-[1,2-c]quinazoline (2) and phenyl-5,5′,6,6′-dihydrobenzo-[4,4′,5,5′]imidazo-[1.1′,2-c,2′-c]quinazoline (3) have been synthesized. Structures of 1 and 3 have been authenticated crystallographically. Quinazolines 1–3 exhibit highly selective 'on-off' switching for Hg2+ ions. The fluorescence intensity displayed a linear relationship with respect to Hg2+ concentration (0.1–1.0 μM; R2 = 0.99) with detection limit of 2.0 × 10−7 M.