Insights into the molecular, optical, thermal, and spectroscopic properties of a novel copper(II) oxalate-organic ligand complex: an experimental and computational perspective.

An innovative organic-inorganic composite material, [Cu2Cl6(C2O4)](C3H5N2)4, was successfully synthesized via an aqueous route and comprehensively characterized. Single-crystal X-ray diffraction revealed its crystallization in the triclinic system (P1¯space group), featuring an asymmetric unit comprising four cationic motifs and two anionic entities interconnected by extensive hydrogen bonding. X-ray powder diffraction confirmed the sample's purity. Thermal analysis (TGA/DTA) indicated the compound's stability up to 320 K, detailing its multi-stage decomposition. Optical analyses demonstrated significant luminescent behavior, highlighting its potential for optoelectronic applications. Density Functional Theory (DFT) calculations provided critical insights into the material's electronic structure and reactivity. Natural Bonding Orbital (NBO) analysis precisely predicted charge transfer within the complex, while the calculated HOMO-LUMO gap further corroborated its promising optical properties. Notably, the compound exhibits remarkable nonlinear optical (NLO) properties, with the computed hyperpolarizability (βo) being 210 times higher in water solution compared to the gas phase, emphasizing the significant impact of solvent environment, particularly green solvents, on its NLO response. The effect of implicit solvents on NLO properties has been theoretically analyzed by using SDM model. The βo response was 210 times higher in solvent (water) compared to the response in the gas phase. These findings underscore the potential of this new hybrid material for advanced functional applications.