Structural studies and detection of nitroaromatics by luminescent 2D coordination polymers with angular dicarboxylate ligands

Abstract

Luminescent two dimensional coordination polymers (CPs) {[Cd(SDB)(H₂O)]·3H₂O}_n1 and {[Zn₃(μ-OH)₂(SDB)₂]·(PPZ)}_n2, (where SDB = 4,4′-sulfonyldibenzoate; PPZ = piperazine) have been synthesized by solvothermal methods. The crystal structure of 1 revealed that the carboxylate moieties of the SDB ligands are involved in “paddle wheel” type coordination with the metal nodes to engender a double chain loop which is further connected by μ-2 type coordination from one of the carboxylate oxygens, generating a two dimensional coordination polymer. In the case of 2, the two dimensional framework is constructed by bridging the one dimensional tri-metallic (Zn₃μ₃-OH) strands with the SDB ligand with a cylindrical cavity occupied by a piperazine moiety. Comprehensive characterization of both pristine compounds 1 and 2 by various physico-chemical methods, structural analysis and photoluminescence properties of activated CPs 1′ and 2′ towards the detection of nitroaromatics have been investigated. Both activated compounds 1′ and 2′ showed sensing of nitro explosive TNP (2,4,6-trinitrophenol) compared to other nitro analytes by fluorescence quenching properties.