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 Cu2+ ion in presence of other metal ions, giving similar to 20 fold increase in fluorescence intensity. The apparent association constant (K-a) for Cu2+ was found to be 2.62 x 10(4) M-1. The intracellular Cu2+ imaging behaviour of chemosensor 1 on HeLa cells studied by fluorescence microscopy revealed that after incubation with 1 cells exhibited intensive fluorescence when exogenous Cu2+ was introduced into the cell. Thus this probe features the ready availability, high sensitivity and selectivity towards Cu2+ in MeCN-H2O (1 : 1, v/v) with cell imaging possibilities with no or negligible cytotoxicity.