Investigation of New Copper(II) Complexes Derived from Carbimazole and Alanine/Phenylalanine Amino Acids: DFT, Molecular Docking, and Bioactivity Evaluation

Abstract

This research investigated the synthesis and characterization of copper(II) complexes, CuCarAla and CuCarPhe, derived from carbimazole (Car) and amino acids (Alanine (Ala), or Phenylalanine (Phe)). The complexes exhibited remarkable thermal stability, with melting points surpassing 300 °C, and high yielding efficiencies of 88 % and 85 %, respectively. Conductivity measurements confirmed their non-electrolytic nature. Fourier-transform infrared (FT-IR) spectroscopy revealed significant shifts in vibrational frequencies, confirming coordination through nitrogen, sulfur, and oxygen atoms, while UV–visible spectroscopy highlighted d–d transitions consistent with an octahedral geometry. Thermal gravimetric analysis elucidated decomposition pathways, showing the absence of hydration water and the presence of coordinated water. Density Functional Theory (DFT) calculations provided insights into the electronic properties revealing lower energy gaps and enhanced reactivity compared to the free ligands. The complexes exhibited significant electron donation capabilities, with E_HOMO values of −4.36 eV and −4.09 eV for CuCarAla and CuCarPhe, respectively. The in vitro bioactivity was assessed against various bacterial and fungal strains, revealing significantly improved antibacterial and antifungal activities. Notably, the copper complexes exhibited inhibition zones of 20–22 mm against bacterial strains and 24 mm against Aspergillus flavus, along with promising anti-inflammatory activity comparable to the standard drug Ibuprofen. Molecular docking indicated enhanced binding affinities for the copper complexes, emphasizing their potential in therapeutic applications.