Tuning Anti-Biofilm Activity of Manganese(II) Complexes: Linking Biological Effectiveness of Heteroaromatic Complexes of Alcohol, Aldehyde, Ketone, and Carboxylic Acid with Structural Effects and Redox Activity

The constantly growing resistance of bacteria to antibiotics and other antibacterial substances has led us to an era in which alternative antimicrobial therapies are urgently required. One promising approach is to target bacterial pathogens using metal complexes. Therefore, we investigated the possibility of utilizing series of manganese(II) complexes with heteroaromatic ligands: Alcohol, aldehyde, ketone, and carboxylic acid as inhibitors for biofilm formation of Pseudomonas aeruginosa. To complete the series mentioned above, Mn-dipyCO-NO(3) with dipyridin-2-ylmethanone (dipyCO) was isolated, and then structurally (single-crystal X-ray analysis) and physicochemically characterized (FT-IR, TG, CV, magnetic susceptibility). The antibacterial activity of the compounds against representative Gram-negative and Gram-positive bacteria was also evaluated. It is worth highlighting that the results of the cytotoxicity assays performed (MTT, DHI HoloMonitorM4) indicate high cell viability of the human fibroblast (VH10) in the presence of the Mn(II) complexes. Additionally, the inhibition effect of catalase activity by the complexes was studied. This paper focused on such aspects as studying different types of intermolecular interactions in the crystals of the Mn(II) complexes as well as their possible effect on anti-biofilm activity, the structure–activity relationship of the Mn(II) complexes, and regularity between the electrochemical properties of the Mn(II) complexes and anti-biofilm activity.