Synthesis, structure and application of a simple cadmium(II)-terpyridine complex as sensor material for selective detection of pyrophosphate anion

Abstract

A simple 1:1 cadmium (II) complex CdCl2L of 4´-[4-(4-aminophenyl)phenyl]- 2,2′:6′,2"-terpyridine ligand L was synthesized, and structure was established by 1H NMR and single-crystal X-ray diffraction study. The crystal structure revealed that Cd(II) ion in the complex adopted a distorted trigonal bipyramidal geometry, and coordinated to three nitrogen atoms of the terpyridine domain and two chlorine atoms. The complex shows selective detection of pyrophosphate anion (P2O74−, PPi) compared to a variety of different anions (HCO3−, I −, SO42−, S2O32−, Cl−, CH3COO−, CO32−, Br−, SO32−, H2PO4−, HPO42−, F−, NO3−) in CH3CN-H2O solution (15:1 v/v) buffered with HEPES, with the lowest limit of detection (LOD) for PPi ion ∼ 2.4 µM. UV-Visible absorption spectroscopy and colorimetric method were used in the detection study. The DFT calculations provide a plausible explanation for the observed selectivity since the PPi is the sole anion capable of substituting the ligand in the CdCl2L complex due to its ability to form a six-membered chelate ring.