Synthesis, characterization, crystal structure and theoretical approach of Cu(II) complex with 4-{(Z)-[(2-hydroxybenzoyl)hydrazono]methyl}benzoic acid

The metal complex of [CuL2]·2DMF (L = 4-{(Z)-[(2-hydroxybenzoyl)hydrazono]methyl}benzoic acid, DMF = N,N-dimethylformamide) (1) had been synthesized and characterized by spectral method(IR), UV–Vis electronic absorption spectra, fluorescence spectra, elemental analysis, electrochemistry, thermal analysis (TG, DTG) and single crystal X-ray diffraction techniques. In the complex, the ligands act as univalent anion bidentate and coordination takes place in the enol tautomeric form with the enolic oxygen and azomethine nitrogen atoms. Molecular geometry from X-ray experiment of the title compound in the ground-state has been compared using the density functional method (B3LYP) and LANL2DZ basis set. DFT calculations at B3LYP/LANL2DZ level of theory prove that the electronic spectra of CuL2·2DMF is attributed to intra-complex electronic transitions as well as π–π* electronic transitions. Also, Mulliken charge analysis, natural bond orbitals (NBO), Wiberg bond index and frontier molecular orbitals (FMO) were performed at B3LYP/LANL2DZ level of theory. In addition, complex 1 exhibits strong photoluminescent emission at room temperature. The electrochemical studies reveal that redox of Cu2+/Cu+ in the complex are quasi-reversible processes. The result of TG analysis shows that the title complex was stable under 100.0 °C.

► Copper complex had been synthesized and characterized.
► The tautomeric enol forms of ligand were indicated in the complex.
► Complex engendered strong fluorescence emission in blue region.
► Electronic transition of complex is intra-ligand transitions.
► DFT calculation results are good agree with experimental data.