A new mononuclear copper(II) complex [Cu(HL)2] (1), has been synthesized from a Schiff base ligand (H2L) and characterized by FTIR spectroscopy, UV-Vis spectroscopy, single crystal X-ray diffraction, and powder X-ray diffraction. Single crystal X-ray diffraction analysis established the perfect square planar geometry around the Cu(II) ion (τ4 ≈ 0), obtained by the coordination of the two N and two O atoms from the two deprotonated H2L ligands. However, the electronic spectra of complex 1 displayed a d−d transition band at 959 nm (ε = 73.5 L mol−1 cm−1) in the MeCN (10–3 M) suggesting a moderate distortion towards the Tetrahedral geometry in the solution. The DFT-optimized structure of complex 1 in the MeCN solvent further supported the distortion of square-planar complex 1 with τ4 ≈ 0.286. Complete active space self-consistent field (CASSCF) calculations in MeCN also suggested a peak at 991 nm ( d_xy→d_(x^2-y^2 )) which is a very good match with the experimental one. The existence of the intermolecular hydrogen bonding interactions (O-H···O, 2.012(13) Å) was supported by the Hirshfield surface analysis. Complex 1 was screened for its potential application as a catalyst for the catalytic oxidation of 3,5-di-tert-butyl-catechol (3,5-DTBCH2) and the turnover number (kcat) was found to be 19.87 h-1 in MeCN. We further explored the protein binding interaction ability of complex 1 with Bovine serum albumin (BSA) protein using a UV-Vis absorption study and the binding constant (Kb) was determined to be 7.15 ×103 M-1. Additionally, Simulation analysis was performed on BSA and Human serum albumin (HSA) proteins with complex 1 to gain a more detailed perception of binding interactions at the atomistic level. The Simulation study indicated that complex 1 interacted more strongly with the BSA with a total of 7 polar interactions than HSA, which has 6 polar interactions. The most stable interaction with BSA had an energy minimum of -8.6 kcal/mole with “0” RMSD.

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