Multi-Ce^III-Inserted Phospho(III)tungstate Containing Three Building Units with Prominent Peroxidase-Mimicking...

An attractive isonicotinic acid-ornamented octa-Ce^III-inserted phospho(III)tungstate [H₂N(CH₃)₂]₆Na₈[Ce₈(H₂O)₃₀W₈Na₂O₂₀(INA)₄][HP^IIIW₄O₁₇]₂[HP^IIIW₉O₃₃]₄·30H₂O (1-Ce) (HINA = isonicotinic acid) has been isolated through the deliberately designed one-step assembly strategy, in which the HPO₃^2- heteroanion template was introduced into the Ce³⁺/WO₄^2- system in the presence of HINA. The polyoxoanion of 1-Ce consists of two identical [Ce₄(H₂O)₁₅W₄NaO₁₀(INA)₂][HP^IIIW₄O₁₇][HP^IIIW₉O₃₃]₂}^7- subunits linked by Ce-O-W bonds. The polyoxoanion exhibits three kinds of polyoxotungstate building blocks [W₄NaO₂₀(INA)₂]^17-, [HP^IIIW₄O₁₇]^6-, and [HP^IIIW₉O₃₃]^8-, in which [W₄NaO₂₀(INA)₂]^17- and [HP^IIIW₄O₁₇]^6- building units can be considered as seeds driven by the coordination of additional Ce³⁺ ions to induce aggregation of [HP^IIIW₉O₃₃]^8- fragments. Furthermore, 1-Ce possesses high peroxidase-like activity and can oxidize 3,3',5,5'-tetramethylbenzidine in the presence of H₂O₂ with a turnover rate of 6.20 × 10^-3 s^-1. Because l-cysteine (l-Cys) can reduce oxTMB to TMB, the detection of l-Cys was established based on the 1-Ce-based H₂O₂ colorimetric biosensing platform with the linear range of 5-100 μM and the limit of detection of 4.28 μM. This work not only can expand the scientific research studies on coordination chemistry and materials chemistry of rare-earth-inserted polyoxotungstates but also can provide practical application possibility in clinical diagnosis using liquid biopsy.