A Zn2+-responsive highly sensitive fluorescent probe and 1D coordination polymer based on a coumarin platform

Abstract

A coumarin-based Schiff base (receptor 1) exhibited fluorescence enhancement selectively with Zn²⁺ at a nanomolar level in near-aqueous medium (EtOH–H₂O; 1 : 1, v/v). The response was instantaneous with a detection limit of 3.26 × 10⁻⁹ M. The sensing event is supposed to incorporate a combinational effect of intramolecular charge transfer (ICT), chelation-enhanced fluorescence (CHEF) and CN isomerization mechanisms. Various spectroscopic methods, viz. IR, UV-visible, fluorescence and NMR in association with single crystal XRD studies, were used for thorough investigation of the structure of receptor 1 as well as of the sensing event. The Zn²⁺ complex of receptor 1 exhibited a very nice 1D chain coordination polymeric framework in its single crystal XRD.