A new antiferromagnetic Dy6 oxido-material as a multifunctional aqueous phase sensor for picric acid as well as Fe3+ ions

Abstract

Owing to the continuous significance of high nuclearity clusters as sensory materials, an attempt is made to develop a new octahedron like Dy₆ cluster as a promising agent to detect picric acid (PA) and Fe³⁺ in the aqueous phase. A novel oxido-metal (OM)-based inorganic compound was synthesized using a green approach. Single crystal X-ray data ascertained the bonding modes and geometry composition of the cluster [Dy₆(μ₆-O)(μ₃-OH)₈(H₂O)₁₂(NO₃)₆](NO₃)₂(H₂O)₂ (1) containing a distorted octahedral oxido ion (O²⁻) at the center of the hexanuclear cage. The complex was further characterized by spectral and magnetic studies. The variable temperature magnetic susceptibility data indicate an antiferromagnetic interaction existing between Dy^III⋯Dy^III ions with Curie constant 79.55 cm³ K mol⁻¹ and Weiss constant −7.65 K. The cluster displayed intermolecular O–H⋯O and O–N⋯O interactions forming a supramolecular framework. These interactions have been verified by Hirshfeld surface analyses. The Ln discrete material is disclosed as the first aqueous phase dual sensor for picric acid (PA) and Fe³⁺. The complex shows highly sensitive, discriminative and selective sensing behavior for the said species. The sensing mechanism is investigated by spectral titration, time decay and DFT (B3LYP/def2-SVP) studies. The detection limit has been discovered for the present OM towards the sensing of PA and Fe³⁺ ions to be ∼0.03 and ∼0.09 ppb, respectively, and therefore this becomes the first cage as a dual-sensor for an explosive and a metal ion.