Gallium(III)- and Thallium(III)-Encapsulated Polyoxopalladates: Synthesis, Structure, Multinuclear NMR, and Biological Activity Studies

Abstract

Three gallium(III)- and thallium(III)-containing polyoxopalladates (POPs) have been synthesized and structurally characterized in the solid state and in solution, namely, the phosphate-capped 12-palladate nanocubes [XPd₁₂O₈(PO₄)₈]^13- (X = Ga^III, GaPd₁₂P₈; X = Tl^III, TlPd₁₂P₈) and the 23-palladate double-cube [Tl₂^IIIPd₂₃P₁₄O₇₀(OH)₂]^20- (Tl₂Pd₂₃P₁₄). The cuboid POPs, GaPd₁₂P₈ and TlPd₁₂P₈, are solution stable as verified by the respective ³¹P, ⁷¹Ga, and ²⁰⁵Tl nuclear magnetic resonance (NMR) spectra. Of prime interest, the spin-spin coupling schemes allowed for an intimate study of the solution behavior of the Tl^III-containing POPs via a combination of ³¹P and ²⁰⁵Tl NMR, including the stoichiometry of the major fragments of Tl₂Pd₂₃P₁₄. Moreover, biological studies demonstrated the antitumor and antiviral activity of GaPd₁₂P₈ and TlPd₁₂P₈, which were validated to be as efficient as cis-platinum against human melanoma and acute promyelocytic leukemia cells. Furthermore, GaPd₁₂P₈ and TlPd₁₂P₈ exerted inhibitory activity against two herpetic viruses, HSV-2 and HCMV, in a dose-response manner.