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)

[Image: see text] 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).