Aluminum-Substituted Keggin Germanotungstate [HAl(H(2)O)GeW(11)O(39)](4–): Synthesis, Characterization, and Antibacterial Activity

[Image: see text] We report on the new monosubstituted aluminum Keggin-type germanotungstate (C(4)H(12)N)(4)[HAlGeW(11)O(39)(H(2)O)]·11H(2)O ([Al(H(2)O)GeW(11)](4–)), which has been synthesized at room temperature via rearrangement of the dilacunary [γ-GeW(10)O(36)](8–) polyoxometalate precursor. [Al(H(2)O)GeW(11)](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) (183)W, (27)Al NMR and UV–vis spectroscopy. A study on the antibacterial properties of [Al(H(2)O)GeW(11)](4–) and the known aluminum(III)-centered Keggin polyoxotungstates (Al-POTs) α-Na(5)[AlW(12)O(40)] (α-[AlW(12)O(40)](5–)) and Na(6)[Al(AlOH(2))W(11)O(39)] ([Al(AlOH(2))W(11)O(39)](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(NO(3))(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.