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

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 [XPd 12 O 8 (PO 4 ) 8 ] 13- (X = Ga III , GaPd 12 P 8 ; X = Tl III , TlPd 12 P 8 ) and the 23-palladate double-cube [Tl 2 III Pd 23 P 14 O 70 (OH) 2 ] 20- ( Tl 2 Pd 23 P 14 ). The cuboid POPs, GaPd 12 P 8 and TlPd 12 P 8 , are solution stable as verified by the respective 31 P, 71 Ga, and 205 Tl 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 31 P and 205 Tl NMR, including the stoichiometry of the major fragments of Tl 2 Pd 23 P 14 . Moreover, biological studies demonstrated the antitumor and antiviral activity of GaPd 12 P 8 and TlPd 12 P 8 , which were validated to be as efficient as cis -platinum against human melanoma and acute promyelocytic leukemia cells. Furthermore, GaPd 12 P 8 and TlPd 12 P 8 exerted inhibitory activity against two herpetic viruses, HSV-2 and HCMV, in a dose-response manner.