Metal ion-assisted ring-opening of a quinazoline-based chemosensor: detection of copper(II) in aqueous media.

A quinazoline-based fluorescence chemosensor, 6-phenol-2-yl-(5,6-dihydrobenzimidazo[1,2-c])quinazoline (HL), for highly selective recognition of Cu(II) in aqueous media was synthesized. The detection limit was of the order of 10(-6) M. The crystal structures of the Cu(II) and Cd(II) complexes showed that HL changed to a Schiff base when it reacts with metal salts and that the metal ions coordinate with two nitrogen atoms and one hydroxyl oxygen atom from the Schiff base. The theoretical calculations at B3LYP-SCRF/6-31G(d) confirmed that it is the Cu(II) ion that assisted the ring-opening of the quinazoline derivative, forming a Cu(II) Schiff base complex during the detection. LMCT leads to the disappearance of fluorescence. A cell imaging study indicated that HL could be used to detect the intracellular Cu(2+) ion.