Synthesis, Characterization, and Phosphoesterase Activity of a Series of 4f- and 4d-Sandwich-Type Germanotungstates [( n -C 4 H 9 ) 4 N] l / m H 2 [(M(H 2 O) 3 )(γ-GeW 10 O 35 ) 2 ] (M = Ce III , Nd III , Gd III , Er III , l = 7; Zr IV , m = 6).

We report on a family of five new 4f- and 4d-doped sandwich-type germanotungstates with the general formula [( n -C ₄ H ₉ ) ₄ N] _{l / m} H ₂ [(M(H ₂ O) ₃ )(γ-GeW ₁₀ O ₃₅ ) ₂ ]·3(CH ₃ ) ₂ CO [M(H ₂ O) ₃ (GeW ₁₀ ) ₂ ] (M = Ce ^III , Nd ^III , Gd ^III , Er ^III , l = 7; Zr ^IV , m = 6), which have been synthesized at room temperature in an acetone-water mixture. Among the compound series, [Zr(H ₂ O) ₃ (GeW ₁₀ ) ₂ ] ^{8 -} , which has been obtained in the presence of 30% H ₂ O ₂ , represents the first example of a 4d-substituted germanotungstate incorporating the intact dilacunary [γ-Ge ^IV W ₁₀ O ₃₆ ] ^8- building block. All compounds were characterized thoroughly in the solid state by single-crystal and powder X-ray diffraction (XRD), IR spectroscopy, thermogravimetric analysis (TGA), and elemental analysis and in solution by NMR and UV-vis spectroscopy. The phosphoesterase activity of [Ce(H ₂ O) ₃ (GeW ₁₀ ) ₂ ] ^9- and [Zr(H ₂ O) ₃ (GeW ₁₀ ) ₂ ] ^8- toward the model substrates 4-nitrophenyl phosphate (NPP) and O , O -dimethyl O -(4-nitrophenyl) phosphate (DMNP) was monitored with ¹ H- and ³¹ P-NMR spectroscopy revealing an acceleration of the hydrolytic reaction by an order of magnitude ( k _corr = 3.44 (±0.30) × 10 ^-4 min ^-1 for [Ce(H ₂ O) ₃ (GeW ₁₀ ) ₂ ] ^9- and k _corr = 5.36 (±0.05) × 10 ^-4 min ^-1 for [Zr(H ₂ O) ₃ (GeW ₁₀ ) ₂ ] ^8- ) as compared to the uncatalyzed reaction ( k _uncat = 2.60 (±0.10) × 10 ^-5 min ^-1 ). [Ce(H ₂ O) ₃ (GeW ₁₀ ) ₂ ] ^9- demonstrated improved antibacterial activity toward Moraxella catarrhalis (MIC 32 μg/mL), compared to the unsubstituted [GeW ₁₀ O ₃₆ ] ^8- POM (MIC 64 μg/mL).