A 7-nitrobenz-2-oxa-1,3-diazole based highly sensitive and selective turn-on chemosensor for copper(II) ion with intracellular application without cytotoxicity.

A 7-nitrobenz-2-oxa-1,3-diazole (NBD) derived turn-on fluorescent probe (1) exhibits a reversible binding to Cu(2+) ion in presence of other metal ions, giving ~20 fold increase in fluorescence intensity. The apparent association constant (K(a)) for Cu(2+) was found to be 2.62 × 10(4) M(-1). The intracellular Cu(2+) imaging behaviour of chemosensor 1 on HeLa cells studied by fluorescence microscopy revealed that after incubation with 1 cells exhibited intensive fluorescence when exogenous Cu(2+) was introduced into the cell. Thus this probe features the ready availability, high sensitivity and selectivity towards Cu(2+) in MeCN-H(2)O (1:1, v/v) with cell imaging possibilities with no or negligible cytotoxicity.