Selective coordination ability of sulfamethazine Schiff-base ligand towards copper(II): Molecular structures, spectral and SAR study

In the present work, a combined experimental and theoretical study of the N-(4,6-Dimethyl-pyrimidin-2-yl)-4-[(2-hydroxy-benzylidene)amino] benzenesulfonamide ligand (H₂L) and its mononuclear and magnetically diluted binuclear Cu^II complexes has been performed using IR, TG/DTA, magnetic, EPR, and conductivity measurements. Calculated g-tensor values showed best agreement with experimental values from EPR when carried out using the MPW1PW91 functional. Coordination of H₂L to a Cu^II center, regardless of the binding site and Cu:L stoichiometry, leads to a significant decrease in the antibacterial activity compared to the free ligand as well as reference drugs in the case of Staphylococcus aureus. Structural-activity relationship suggests that E_LUMO, ΔE, dipole moment, polarizability and electrophilicity index were the most significant descriptors for the correlation with the antibacterial activity.