Polyoxometalates electrostatic interactions

Chen et al. recently reported the stable ruthenium-oxo-oxalato cluster Na7[Ru4(p3-0)4(C204)g] (2) (Fig. lc) as a particularly potent inhibitor of HIV-1 reverse transcriptase (RT) with an IC50 value of 1.9 nM [17], Apparently, the polyanionic cluster mimics poly anionic nucleic acid in its binding to HIV-1 RT through electrostatic interactions. The cluster shows promising anti-HIV-1 activity without being cytotoxic. In contrast to many polyoxometallates, this cluster has been demonstrated to be stable under physiological conditions. 

A recent communication reported an interesting ferrocene-anion solid state interaction between Compound 121 and polyoxometalate anions (Fig. 15) (235). An electrostatic interaction between the trimethylammonio group and the an-... 

Figure 15 Vesicle template-directed self-assembly of a core-shell structure with ring-shaped polyoxometalates on the surface through electrostatic interactions between the cationic amphiphiles and the polyanionic ring.

Polyoxometalates are able to act as ligands for different redox-active transition metals (M ) such as iron, manganese, cobalt and ruthenium or d metals (such as zirconium, hafnium, titanium). The coordination of a heterometal by a polyoxometalate framework takes place either through the superficial coordination of a metal cation by electrostatic interaction, or by incorporation of the transition metal within the POM structure resulting in the formation of transition metals substituted polyoxometalates (TMSPs), which generally exhibit a higher stability. 

Independent of mechanistic details, this process reduces O2 and oxidizes MoO. The thermodynamic endpoint is molybdate (Mo04 ), which at physiological pH polymerizes to polyoxometallates, or hetero-polyoxometallates if oxoanions, such as phosphate, are present The formation of 0x0 complexes dis-fevors the interaction of the metal with other ligands and it is no surprise that the decomposition of ALF186 in the presence of HEWL produces a phosphomo-lybdate (Keggin ion), which is electrostatically and not covalently bound to the protein [37]. 

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