Reducing Systematic Uncertainty in Computed Redox Potentials for Aqueous Transition-Metal-Substituted Polyoxotungstates

Anticancer Drug Extraction from Plasma Samples Using Three-Dimensional Polyoxometalate-Based Supramolecular Frameworks as Sorbents

Four self-assembled inorganic-organic hybrid materials, namely, H{Na(H2O)3[Gd(PDA)(H2O)2]3[BW12O40]}·4H2O (1), H{Na(H2O)3[Tb(PDA)(H2O)2]3[BW12O40]}·3H2O (2), H{Na(H2O)3[Er(PDA)(H2O)3]3[BW12O40]}·H2O (3) (PDA = 1,10-phenanthroline-2,9-dicarboxylate), and [Pr3(H2O)13(pydc-OH)2][BW12O40]·12H2O (4) (pydc-OH = 4-hydroxy-2,6-pyridinedicarboxylate), were hydrothermally synthesized and structurally characterized. Hybrids 1-3 are isostructural and contain a Keggin unit, which is linked to lanthanoids to produce distinct trinuclear lanthanoid building blocks. The fragments are connected by anion-π and hydrogen bonding interactions to create 3D networks. In hybrid 4, a trimeric Pr-organic species bearing a Keggin unit forms a 2D coordination polymer, and then hydrogen bonding interactions between 2D layers lead to the formation of a 3D structure. These polyoxometalate-based frameworks were used as sorbents for the dispersive microsolid-phase extraction (D-μSPE) of two anticancer drugs (doxorubicin and epirubicin) in human plasma samples. Analytes were quantified and separated using high-performance liquid chromatography with fluorescence detection (HPLC-FLD). The method's linearity was between 0.8-500 ng mL-1 and 1.0-500 ng mL-1 for the antineoplastic drugs doxorubicin and epirubicin, respectively. The limits of detection (S/N = 3) were in the range of 0.2-0.3 ng mL-1, while the precision was in the range of 3.5-4.3%. Finally, human plasma samples from patients treated with doxorubicin or epirubicin were analyzed by using the D-μSPE-HPLC-FLD method.

Computation of 31P NMR chemical shifts in Keggin-based lacunary polyoxotungstates

Density Functional Theory (DFT) calculations were employed to systematically study the accuracy of various exchange-correlation functionals in reproducing experimental 31P NMR chemical shifts, δExp(31P) for Keggin, [PW12O40]3- and corresponding lacunary clusters: [PW11O39]7-, [A-PW9O34]9-, and [B-PW9O34]9-. Initially, computed chemical shifts, δCalc(31P) were obtained with without neutralising their charge in which associated error, δError(31P), decreased as a function of Hartree-Fock (HF) exchange, attributed to constriction of the P-O tetrahedron. By comparison, δCalc(31P) performed with explicitly located counterions to render the system charge neutral, reduced discrepancies, δError(31P) by 1-2 ppm. However, uncertainties in δCalc(31P) remain, particularly for [B-PW9O34]9- anions attributed to direct electrostatic interactions between the counterions and the central tetrahedron. Optimal results were achieved using the PBE/TZP//PBE0/TZP method, achieving a mean absolute error (MAE) and a mean squared error (MSE) of 4.03 ppm. Our results emphasize that understanding the nature of the electrolyte and solvent environment is essential to obtaining reasonable agreement between theoretical and experimental results.