A new water-soluble copper(II) complex as a selective fluorescent sensor for azide ion

{[Cu-2(H2L)(OH)(H2O)]center dot(ClO4)(2)(H2O)} (1) serves as a selective azide ion fluorescent sensor in aqueous medium. 1 binds with N-3(-) to give [Cu-6(HL)(2)(mu(1,1)-N-3)(6)] (2) which imposes rigidity and decreases the non-radiative decay of the excited state to give rise to fluorescent enhancement. 1 is highly selective over other various anions in aqueous medium.