The Effect of Anion, Steric Factors on the Catalytic Activity of Hydrogen Peroxide, Biological Activities, Docking, and DFT Calculations of Novel Mixed Ligand of Copper Complexes

Mixed-ligand Cu (II) complexes with the empirical formula [Cu(N-N)(Hfac)]X have been produced, where N-N represents 2,2′-Bipyridine (Bipy), 1,10-phenanthroline (Phen), or 4,7-diphenyl-1,10-phenanthroline (Diphen), HfacH denotes hexafluoroacetylacetone, and X signifies the counter ion (Cl⁻ or ClO₄⁻). Comprehensive physicochemical analyses, encompassing elemental analysis, UV–visible spectroscopy, FT-IR spectroscopy, TGA, ESR, mass spectrometry, XRD, magnetic measurements, and molar conductance assessments, have been conducted. The thermal stability of all complexes was assessed using TGA analysis, and the kinetic parameters were derived using the Coats–Redfern method. The degree of crystallinity and the unit cell of all compounds were ascertained using XRD measurements. A square planar geometric configuration is suggested for CuHfBP and CuHfPhP complexes, while octahedral or tetrahedral geometry is recommended for the other complexes. The copper mixed-ligand complexes demonstrate significant catalytic activity in the decomposition of hydrogen peroxide through a first-order process. The stability sequence of ternary complexes concerning their ligands is as follows: Bipy > o-Phen > Diphen. Additionally, both the ligands and all metal complexes were optimized by theoretical analysis using a DFT/B3LYP/LANL2DZ basis set to ascertain the theoretical stability of these metals and to identify FMO orbitals, TDOS, ESP, energy gap, and physical computational parameters, which indicate the stability of these complexes. Additionally, the synthesized complexes exhibited antimicrobial and antitumor activities against HNSCC cancer cell and showed that the presence of the phenyl rings makes the delocalization of electrons and increases the activities of them. Moreover, the docking stimulation of these complexes with PDBID:3HUN, 3 t88, and 3ayk showed their various binding activities and confirmed the experimental results.