Syntheses and crystal structures of new aurate salts of adenine or guanine nucleobases.

Two new gold(III) complexes with adenine or guanine nitrogenous bases as counter-cations were synthesized. These are 6-amino-7H-purine-1,9-diium tetrachloridogold(III) chloride monohydrate, (C₅H₇N₅)[AuCl₄]Cl·H₂O, 1, and 2-amino-6-oxo-6,7-dihydro-1H-purin-9-ium tetrachloridogold(III) hemihydrate, (C₅H₆N₅O)[AuCl₄]·0.5H₂O, 2. Their crystal structures were studied using single-crystal X-ray diffraction and FT–IR spectroscopic techniques. The arrangement of species in the studied crystal structures implies π-stacking interactions, as well as concomitant C—H...π interactions, hydrogen bonds and other types of noncovalent interactions, which were studied qualitatively and quantitatively using the method of molecular Voronoi–Dirichlet polyhedra. The variation of the nitrogenous base from adenine to guanine results in evident differences in the packing of the species in the crystals of 1 and 2. The splitting and shifting of bands in the FT–IR spectra of the title compounds reveals several features representative of noncovalent interactions in their crystal structures.