Antimicrobial activity of topcoat formulation based on synthesized new cyclodiphosph(V)azane derivatives as a biocide for protective coatings

Abstract Novel cyclodiphosph(V)azane sulfonamide ligands and their corresponding Cu²⁺ and Cd²⁺ metal complexes were synthesized and evaluated as antimicrobial additives for coating applications. The structures of the prepared compounds were confirmed using standard spectroscopic techniques. The synthesized compounds were incorporated into paint formulations, and the resulting coatings were systematically assessed for their mechanical, physical, and antimicrobial properties. The modified coatings exhibited enhanced physico-mechanical performance, with gloss values of 80–95, hardness ranging from 7 H to 9 H, adhesion improved from 4B to 5B, and impact resistance increased from 1.3 to 2.5 J. Antimicrobial activity was evaluated using the agar well diffusion method against representative Gram-positive and Gram-negative bacteria, as well as fungal strains. The cadmium complex demonstrated the highest activity, with inhibition zones ranging from 31.8 to 46.0 mm, while the copper complex showed moderate activity and the free ligand exhibited selective effects. Although incorporation into the coating matrix led to a reduction in antimicrobial activity, the coatings retained appreciable effectiveness against selected strains. The results indicate that cyclodiphosph(V)azane-based metal complexes are promising multifunctional additives for antimicrobial coatings, combining improved mechanical performance with significant biological activity.