A New Polyoxovanadate Based Hybrid Materials: A Promising Sensor for Picric Acid and Pd2+ Found in the Aqueous Environment

Abstract

Apart from traditional metal-organic frameworks as sensitive materials, discrete cages or clusters to sense hazardous species are uncommon. Keeping this view in mind, a new hybrid discrete material of decavanadate anion and copper complex cations is designed for the purpose. A novel polyoxovanadate (POV)-based inorganic-organic hybrid compound showing the unique combination of first anagostic(V···H) interaction was synthesized. Single crystal X-ray data ascertained the bonding modes and geometry of the complex along with novel anagostic weak intermolecular interactions in the complex material. X-ray crystallography confirmed the composition of the cluster to be {Cu(Pyno)4}{NEt3H}2[H2V10O28] (1), containing decavanadate as an anion with square planar copper(II) complex and triethylammonium as cations. The compound was further characterized by FTIR, time decay and magnetic studies. Magnetic studies confirmed the presence of the Cu2+ state in the complex at RT as well as low temperature. The cluster displayed rare intermolecular V⋯H, lp⋯π, V–O⋯H, π⋯π and C–H⋯H interactions, which generate a supramolecular framework. Hirshfeld surface analyses have verified these interactions. The hybrid material is disclosed as the first aqueous phase sensor for picric acid (PA) as well as Pd2+. The complex shows highly sensitive, discriminative and selective sensing behavior for the said species and is the first example of its type in discrete molecule category. The sensing pathways are investigated by spectral titrations, time decay, and DFT (B3LYP/def2–SVP) studies. The lowest detection limit has been discovered for the present POV towards the sensing of both PA and Pd2+ ions with ~0.18 and ~0.80 ppb, respectively.