Synthesis, XRD/HSA-Interactions, QTAIM Analysis, Optical and Nonlinear Optical Responses Studies of Cu(II) Complex with the Schiff Base Ligand Derived from 5-Bromosalicylaldehyde

In this study, we efficiently synthesized a new Schiff base ligand (H2L) along with its mononuclear complex Cu(II) (1). The chemical structures of these compounds were rigorously determined using various analytical techniques, including UV- Vis., FT-IR, 1H NMR, 13 C NMR CHN elemental analysis, single crystal X-ray diffraction, and quantum calculations. The X-ray diffraction analysis of the complex revealed the presence of intermolecular interactions characterized by C-H center dot center dot center dot Br hydrogen bonds, leading to the formation of 2D layers. We conducted a systematic investigation of these intermolecular interactions using HS and QTAIM analysis. Additionally, we affected a comprehensive analysis of H2L, 1, and 2, focusing on their structural, electronic, and optical properties using DFT and TD-DFT calculations in gas and solvent. The computed parameters closely matched the experimental data, demonstrating good agreement. Reactivity parameters indicated that complex 2 exhibited lower hardness (similar to 1.7 eV) compared to 1 (similar to 1.8 eV) and H2L (similar to 4.4 eV). NLO analysis revealed substantial alpha and beta values for compound 2 in both static and dynamic regimes. Notably, the beta values of the title complexes increased with higher solvent polarity. In summary, our investigation highlights the potential of the title complexes as promising candidates for second-order nonlinear optical materials.