A fluorescent zinc(II)-based layered complex for selective sensing of Cr₂O₇^2– and Fe³⁺ ions in water system

Abstract

A new Zn(II)-organic framework with 2,2-bipyridine-5,5-dicarboxylate (bpydc) ligand {[Zn(H₂O)(bpydc)]·CH₃OH}_n has been obtained solvothermally, followed by structural and photophysical characterization. Structural analysis reveals that the distorted Zn²⁺ octahedra are periodically extended by the ditopic bpydc^2‒ connector, leading to a coplanar grid-like (4 4) layer. The complex exhibits excellent thermal and environmental stability as well as good dispersion in water system. More interestingly, resulting from the efficient ligand to metal charge transfer, the complex has been observed to emit strong blue emission dispersed in water medium enabling the detection of both Cr₂O₇^2– and Fe³⁺ ions through fluorescence quenching with large quenching constants (1.12X10⁵ M^-¹ and 2.12X10⁴ M^-¹) and low limits of detection (0.54 μM and 1.02 μM). These interesting results suggest that the complex can potentially serve as a promising dual-responsive luminescent sensor material for environmental pollutant monitoring.