A new coordination polymer of Cd(II) with 4-methyl-1,2,4-triazole-3-thiol ligand: synthesis, characterization, crystal structure, photoluminescence and DFT calculation

Abstract

A new Cadmiun(II) coordination polymer, {[Cd(µ-mptrz)₂].0.5((CH₃)₂SO)}_n was prepared from the reaction of CdBr₂ with 4-methyl-4H-1,2,4-triazole-3-thiol (Hmptrz) ligand in methanol. The coordination polymer was thoroughly characterized by elemental analysis, IR, UV–Vis, ¹HNMR spectroscopies, and thermogravimetric analysis. Moreover, its structure was studied by the single-crystal diffraction method. Compound 1 has a 1D chain structure. Furthermore, crystal structure is stabilized by intermolecular weak interactions, for example, C–H···O, C–H···N, and C–H···S hydrogen bonds. Besides, the photoluminescence of 1 has been investigated. This compound exhibits photoluminescence with an emission maximum of 321 nm upon excitation at 259 nm. The present work is a combined experimental and computational study. Quantum chemical parameters such as bond lengths, bond angles, HOMO–LUMO energy levels, energy band gap \(\Delta E\), chemical hardness η, the dipole moment μ, and Natural bond orbital (NBO) analysis of the compound were investigated using the DFT at M06/GENECP (6-31 g(d) and LANL2DZ) basis sets for compound 1. Our calculation results have shown that compound 1 has an energy band gap (∆E = 3.857 eV), indicating a high recommendation for a semiconductor compound. The optimized geometry of the Cd(II) coordination polymer is shown in good agreement with single crystal X-ray data. UV/Vis spectra are calculated with the time-dependent density functional theory (TD-DFT) method. Furthermore, TD-DFT displays intraligand transition (ILCT) between triazole bridging ligands. Moreover, NBO analysis of the Cd(II) coordination polymer indicates that the lone pair donor orbital interaction between the N, S, and O lone pairs and π*, σ* anti-bonding orbitals provides stronger stability. Additionally, Solid-state density functional theory (DFT) calculations were performed on 1 using the program VASP to understand the electronic states and conduction pathways of the coordination polymer.