engleski

Aluminum-substituted Keggin germanotungstate [HAl(H2O)GeW11O39]4–: synthesis, characterization, and antibacterial activity

We report on the new monosubstituted aluminum Keggin-type germanotungstate (C4H12N)4[HAlGeW11O39(H2O)]·11H2O ([Al(H2O)GeW11]4−), which has been synthesized at room temperature via rearrangement of the dilacunary [γ-GeW10O36] 8− polyoxometalate precursor. [Al(H2O)GeW11] 4− has been characterized thoroughly both in the solid state by single- crystal and powder X-ray diffraction, IR spectroscopy, thermogravimetric analysis, and elemental analysis as well as in solution by cyclic voltammetry (CV) 183W, 27Al NMR and UV−vis spectroscopy. A study on the antibacterial properties of [Al(H2O)GeW11]4− and the known aluminum(III)-centered Keggin polyoxotungstates (Al-POTs) αNa5[AlW12O40] (α- [AlW12O40]5−) and Na6[Al(AlOH2)W11O39] ([Al(AlOH2)W11O39] 6−) revealed enhanced activity for all three Al-POTs against the Gram-negative bacterium Moraxella catarrhalis (minimum inhibitory concentration (MIC) up to 4 μg mL−1 ) and the Gram-positive Enterococcus faecalis (MIC up to 128 μg mL−1 ) compared to the inactive Al(NO3)3 salt (MIC > 256 μg mL−1 ). CV indicates the redox activity of the Al- POTs as a dominating factor for the observed antibacterial activity with increased tendency to reduction, resulting in increased antibacterial activity of the POT.

polyoxometalate ; Keggin-based aluminogermanotungstate ; antibaterial activity ; Moraxella catarrhalis ; Enterococcus faecalis

Bilateral financial funding was provided by the Centre for International Cooperation & Mobility (ICM) of the Austrian Agency for International Cooperation in Education and Research (OeADGmbH) Project HR 06/ 2020 to A.R. and the Project “Biological profiling of polyoxometalates” to Hana Čipčić Paljetak.