Aluminum-Substituted Keggin Germanotungstate [HAl(H₂O)GeW₁₁O₃₉]^4–: Synthesis, Characterization, and Antibacterial Activity

Abstract

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.

Ultralow‐Loading and High‐Performing Ionic Liquid‐Immobilizing Rhodium Single‐Atom Catalysts for Hydroformylation

“…As shown in Figure S3a and b, all samples showed UV‐vis absorption peaks at 200 nm, which belonged to O d →W (O d is the terminal oxygen) charge‐transfer band (CT) and was not affected by the cation and Rh‐substituted POMs [32] . In addition, K‐SiW and K‐PW showed absorption bands at 243 and 246 nm respectively, which belonged to O b /O c →W(O b is bridged between corner‐shared WO 6 octahedra and O c is bridged between edge‐shared WO 6 octahedra) transition and was the characteristic absorption peak of Keggin‐type POMs [33] . The characteristic absorption peaks of K‐SiWRh and K‐PWRh from O b /O c →W transition red‐shifted to 256 and 253 nmdue to mono‐metal(Rh) substituted Keggin‐type structure, respectively.…”

“…[32] In addition, K-SiW and K-PW showed absorption bands at 243 and 246 nm respectively, which belonged to O b /O c !W(O b is bridged between corner-shared WO 6 octahedra and O c is bridged between edge-shared WO 6 octahedra) transition and was the characteristic absorption peak of Keggin-type POMs. [33] The characteristic absorption peaks of K-SiWRh and K-PWRh from O b /O c !W transition red-shifted to 256 and 253 nmdue to mono-metal(Rh) substituted Keggin-type structure, respectively. Similarly, the organic salts such as MTOA-SiWRh, TBA-SiWRh, MTOA-PWRh and TBA-PWRh also gave the characteristic absorption peaks around 260 nm.…”

Hydrocarboxylation of Olefins Catalyzed by Polyoxometalate-Anchored Palladium Single-Atom Catalysts

“…This result is the evidence of the characteristic bands of Keggin-type heteropolytungstates. 46 In the spectra of K-SiWPd and TBA-SiWPd, the absorption peaks of the O b /O c → W transition are also observed and red-shifted to 261 and 258 nm, respectively, compared with those of K-SiW salts. Similarly, a moderately intense band around 252 nm for K-PWPd and 258 nm for TBA-PWPd was also found.…”

A Nickel-Containing Polyoxomolybdate as an Efficient Antibacterial Agent for Water Treatment

“…In 2020, our group reported two Keggin-type Co-POMs with significant antibacterial properties, namely [Co(L) 2 ] 3 [PMo 12 O 40 ] and [Co(L) 2 ] 3 [PW 12 O 40 ] [18]. In 2021, an aluminum-substituted Keggin [Al(H 2 O)GeW 11 ] 4− was synthesized by Rompel's group, and the Al-POM indicated enhanced antibacterial activity compared with simple aluminum salt against Moraxella catarrhalis (MIC = 4 µg/mL) and Gram-positive Enterococcus faecalis (MIC = 128 µg/mL), respectively [19]. Obviously, both polyoxomolybdates and polyoxotungstates exhibit excellent antibacterial activity.…”