Synthesis of Metal–Saccharin Complexes as an Antimicrobial Inorganic Pigment for Surfaces

There is significant concern within the scientific community regarding the prevention and treatment of diseases caused by viruses and bacteria as well as the increasing resistance of these microorganisms to conventional medicines. Numerous studies have addressed this challenge to explore the antimicrobial potential of various compounds and improve existing drugs, aiming to counteract microbial mutations and prevent large-scale outbreaks. This study synthesized and characterized three metal-saccharin complexes (Fe, Co, and Ni) and investigated their application as antimicrobial activity pigments. The complexes were studied using molar conductivity, Fourier transform infrared spectroscopy, mass spectrometry, nuclear magnetic resonance (NMR ¹H), UV-vis spectroscopy, thermogravimetry, single-crystal X-ray diffraction, and colorimetry. The results confirmed the formation and composition of the metal complexes. The synthesized compounds exhibited antimicrobial activity in both solution and solid states, maintaining their efficacy when incorporated into acrylic paste and fabric paint. The Co-sac complex displayed superior antimicrobial activity among the tested complexes across all evaluations. It inhibited the growth of <i>Salmonella typhimurium</i> and <i>Candida albicans</i> at a MIC of 62.5 μg·mL^-1, with fungicidal and bactericidal effects confirmed at 125 μg·mL^-1. In disk diffusion assays, Co-sac (10%) in acrylic paste showed a maximum inhibition halo of 14.03 ± 0.39 mm against <i>Staphylococcus aureus</i>. When applied to face mask fabric, the same complex achieved inhibition halos of up to 11.65 ± 2.25 mm for <i>Escherichia coli</i> and 8.78 ± 2.34 mm for <i>Listeria monocytogenes</i>. Notably, the antimicrobial activity index reached values as high as 1.05, surpassing those of conventional antibiotics in specific tests.