Probing the structure and molecular docking of a Cu(II)-glutamic acid complex as a metallodrug agent using spectroscopic, electrochemical and theoretical studies

Abstract

A copper(II) complex with L-glutamic acid was synthesized and comprehensively characterized to elucidate its structural, electronic, redox, thermal, and biological interaction properties. FT-IR analysis confirmed coordination through carboxylate oxygen and amino nitrogen atoms, evidenced by shifts in ν_as(COO⁻) and ν_s(COO⁻) bands along with the appearance of Cu-O and Cu-N vibrational modes. The electronic spectrum of the Cu(II) complex exhibits a broad and low-intensity d-d transition in the 600-800 nm region, which is characteristic of a Jahn-Teller distorted octahedral geometry; this assignment is further supported by the observed effective magnetic moment (µ_eff = 2.46 BM), consistent with a d⁹ Cu(II) system. Fluorescence analysis shows an emission maximum in the 430-460 nm range with a Stokes shift of approximately 70-100 nm, indicating significant excited-state relaxation and ligand field perturbation arising from coordination of glutamic acid to the Cu(II) center. Thermogravimetric analysis showed major decomposition steps between 167 and 187 °C, confirming the thermal stability of the coordinated framework. Molar conductivity measurements indicated weak electrolyte behavior, suggesting the predominance of a neutral complex species in solution. Cyclic voltammetry demonstrated a quasi-reversible Cu(II)/Cu(I) redox couple with ligand-dependent potential shifts, reflecting coordination-induced modulation of electron density at the metal center. Molecular docking investigations revealed enhanced receptor binding affinity of the Cu(II) complex compared to free glutamic acid, with calculated binding energies reaching up to - 9.20 kcal·mol⁻¹, accompanied by strengthened hydrogen bonding and electrostatic interactions within receptor binding pockets. These combined results establish a clear structure-electronic-biological correlation, demonstrating that coordination-induced changes in electronic structure and redox properties directly influence the binding affinity and interaction behavior of the complex with biological targets.