Double Coordination Compounds of Fe(II)/Co(II)/Ni(II)/Cu(II) 1,10-Phenanthroline/2,2ʹ-Bipyridine Cations with Tartratogermanate(IV) Anions as Novel Nonresistant Antimicrobial Agents

Abstract

Objective. To study the antimicrobial activity of double coordination compounds with 1,10-phenanthroline/2,2ʹ-bipyridine complexes of Fe(II)/Co(II)/Ni(II)/Cu(II) as cations and diff erent tartratogermanate(IV) anions, reveal the main factors of their effi ciency and establish relations between their composition, structure features, and biological properties. Methods. The developed synthesis method allowed us to obtain three diff erent tartratogermanate anions, which exist together in the solution and can be selectively recognized by the certain type of 1,10-phenanthroline/2,2ʹ-bipyridine cation. Th e antimicrobial activity of the compound was investigated by a rapid twofold dilution method in a standard liquid nutrient medium (Hottinger digestion) to determine the minimal inhibitory concentration (MIC) and minimal bactericidal concentration (MBC). Results. Th e complex nature of studied compounds, synergism of their biologically active structural units, and the presence of diff erent types of intermolecular bonds result in the high antimicrobial activity against a wide range of microorganisms such as gram-positive Planococcus citreus, Microcoсcus luteus, Bacillus cereus, Staphylococcus aureus, Streptococcus lactis, and, in a less degree, gram-negative Escherichia coli and Agrobacterium tumefaciens. Compounds (1)—(8) show a high antimicrobial activity because all of them belong to the type of double coordination compounds and contain similar structural units. Nevertheless, complexes (1) (23.44 μg/mL), (3) (46.9 μg/mL), (4) (23.44 μg/mL), and (8) (46.9 μg/mL) turned out to be the most eff ective, while (6) (>500 μg/mL) and (7) (>500 μg/mL) are less productive. Complexes that have anions [Ge2(OH)(H2Tart)(μ-Tart)2]3- (1), (8) and [Ge2(OH)(HTart)(μ-Tart)2]4- (4) with free hydroxyl and carboxyl groups of the terminal tartaric acid are able to interact with metals in the enzymes of microorganisms and appear to be better antimicrobial drugs because they show lower inhibitory and bactericidal concentrations. Conclusions. Structural features such as the cation-anionic type of compounds, variability of intermolecular interactions, joint of diff erent biologically active units and free chelating groups in tartaric ligands lead to the combination of different action mechanisms and exclude the possibility of strain resistance.