Synthesis, characterization and multi-dimensional application approach for two distinctive tetra nuclear, first-time reported, Fe3+/Hg2+ and Fe3+/Cd2+ clusters from a new Fe3+ containing metalloligand

Abstract

A new mononuclear Fe³⁺ metalloligand MC1 [FeLN₃(H₂O)], developed by using the N₂O₂ donor Schiff base ligand H₂L, has been successfully used to detect and remove Hg²⁺ and Cd²⁺ from several transition metal ions with the formation of two unusual hetero metallic μ-oxo Fe³⁺–Hg²⁺/Cd²⁺ clusters, [(Fe₂³⁺)(μ-O)L₂Cl₄(Hg₂²⁺)] (MC2) and [(Fe₂³⁺)(μ-O)L₂I₄Cd₂²⁺] (MC3) [(where H₂L is 6, 6′-(1E, 1′E) (ethane-1, 2 diylbis(azaneylidene))bis(methaneylylidene))bis(2-ethoxyphenol)]. All three complexes were identified by X-ray single-crystal data analysis along with a range of spectral studies. In MC1, the Fe³⁺ is coordinated with deprotonated H₂L, one water molecule, and one azide ion as a secondary anionic residue, forming an octahedral geometry. Interestingly, MC2 and MC3 are isostructural, where each asymmetric unit contains deprotonated H₂L, one Fe³⁺ and Hg²⁺/Cd²⁺ metal center, two Cl⁻/I⁻ and two Fe³⁺ centers are connected by a μ-O bridge to form tetranuclear complexes. As the band gap energy values of MC1, MC2, and MC3 (3.07 eV, 2.69 eV, and 2.55 eV, respectively) are in the visible region so all the three complexes are exposed to investigate their potentiality to be effective Schottky devices and at the same time a thorough inspection has been carried out to check their catalytic behaviour in aqueous medium in terms of methylene blue (MEB) dye degradation under visible light irradiation. A thorough inspection reveals the better MB dye degradation potentiality of MC3 in comparison to MC2 in the presence of H₂O₂. At the same time, the investigation of the device performances, conductivity, and device parameters disclose more effectiveness of MC3 in comparison to MC2 in a better Schottky device. The effectiveness of MC3 in both applications may be attributed to its lower band gap value.