Synthesis and characterization of Sb(V)–adenosine and Sb(V)–guanosine complexes in aqueous solution

Sb(V) is known to form a complex with adenine ribonucleosides suggesting that ribonucleosides may be involved in the mechanism of action of pentavalent antimonial drugs against the parasitic disease leishmaniasis. In this study, Sb(V) complexes with adenosine and guanosine were prepared and characterized. Two Sb(V)–adenosine complexes were obtained in the solid state with either 1:2 or 1:1 Sb(V):adenosine molar ratios. A thermoreversible Sb(V)–guanosine hydrogel was also obtained using Sb:guanosine molar ratios varying from 0.5 to 1. These complexes were characterized by H1 NMR spectroscopy, high resolution eletrospray ionization mass spectrometry, elemental analysis and circular dichroism. For the adenosine complexes, we propose that Sb(V) is either penta-coordinated by two riboses and one hydroxyl anion or octa-coordinated by two riboses and two hydroxyls or by one ribose and four hydroxyls. The Sb(V)–guanosine hydrogel is shown to be composed of a mixture of 1:1 and 1:2 Sb(V)–guanosine complexes, forming nanoassemblies with two types of interactions: (i) covalent bonds forming Sb(V)–guanosine complexes and (ii) intermolecular interactions between the different Sb(V)–guanosine complexes via base stacking.