Synthesis, crystal structure, DFT calculations, detection limit, solvent effect on nonlinear optical properties, and molecular docking of new Schiff-base Cu(II) complex

A new Schiff base ligand (E)-2-[(4-octyloxyphenylimino)methyl]phenol (L) and its Cu(II) complex (CuL₂) were successfully synthesized and characterized by different instrumental techniques such as FTIR, NMR, UV-Vis, and single crystal X-ray. The thermal analysis showed excellent thermal stability of both the L and CuL₂ complex. The single crystal X-ray diffraction analysis revealed that the CuL₂ complex crystallizes in triclinic space group P 1¯ with one and a half independent molecules in the asymmetric unit and one copper atom located on an inversion center. Hirshfeld surface analysis exhibited dominant H…H contacts with a maximum 75.5 % contribution, and no π-π intermolecular interactions were observed. The association constant and detection limit of L toward Cu(II) were found to be 1.69 × 10⁸ M⁻¹ and 0.66 μM, respectively. Furthermore, quantum chemical Density Functional Theory (DFT) calculations revealed that the global reactivity of L and CuL₂ increased with the solvent polarity. The HUMO-LUMO energy gaps of L and CuL₂ were calculated in different polar and nonpolar solvents, yielding ranges of 3.84−3.91 and 3.53−3.62 eV, respectively. Similarly, the computed first hyperpolarizability (β_total), average polarizability (<α>), anisotropy of polarizability (Δα), and dipole moment (μ) of L and CuL₂ were also increased by the increasing solvent's dielectric constant. The molecular docking simulation of L against five breast cancer protein receptors, namely 1H7 K, 7L1X, 5FDO, 4KIK, and 3ERT, showed notable docking scores of −8.8, −8.2, −8.1, −7.8, and −7.6 kcal/mol, respectively. The drug-likeness and ADMET properties of L demonstrated a promising ADMET profile for a potential drug candidate.