Microbiological applications of the saccharinatecopper(II) complex (Cu-Sac)

Abstract

The tetraaqua-bis(saccharinato)copper(II) dihydrate complex (Cu-Sac) was synthesized, structurally characterized by single-crystal X-ray diffraction, and tested for antioxidant and antimicrobial activity. In this complex, deprotonated saccharin ligands coordinate monodentate via nitrogen in a trans configuration to copper, with four water molecules also bound. Its distorted octahedral geometry fits the formula [M(Sac)₂(H₂O)₄]·2H₂O. The Cu-Sac complex showed good antioxidant efficacy in DPPH and hydrogen peroxide scavenging assays and was effective against ten microorganisms in both pellet and solution forms. Notably, this study also assessed the use of the pigment in commercial white paint at 10 % and 20 % concentrations. MIC data indicated that the complex exhibits broad-spectrum antimicrobial activity, showing efficacy against Gram-negative and Gram-positive bacterial strains, and fungicidal activity against yeast strains. The copper saccharinate paint showed promising results in the disk diffusion test, producing inhibition zones of 27.50 ± 4.0 mm for P. mirabilis, exceeding the inhibition zones observed with standard antibiotics. An increase in the concentration of the complex in the paint was also shown to result in greater antibacterial efficacy. The activity index obtained for the paint samples showed good results, with the Cu-Sac 20 % sample being particularly noteworthy, especially against the S. epidermidis and E. faecium strains, with indices ≥1. These findings suggest that the Cu-Sac complex has potential as an antimicrobial pigment or surface-applied antibiotic agent, indicating promising prospects for industrial applications.

Keywords: Antimicrobial; Complex; Copper; Inorganic pigment; Saccharin; Surface protection.