Solution, solid state and biological characterization of ruthenium(III)-DMSO complexes with purine base derivatives

Two new complexes of Ru(III) with purine base derivatives, [ mer-RuCl 3(acv)(DMSO-S)(C 2H 5OH)] · C 2H 5OH ( 1) (acv=acyclovir, DMSO=dimethyl sulfoxide) and [ trans-RuCl 4(guaH)(DMSO-S)] · 2H 2O ( 2) (guaH=protonated molecule of guanine), were prepared from the same Ru(III) precursor, [ trans-RuCl 4(DMSO-S) 2] −, by substitution of one DMSO-S. Coordination of acv induced also replacement of one chloride by an ethanol molecule. This reactivity difference was explained by striking contrasts in the hydrogen bonding schemes of the two complexes, evidenced in their X-ray crystal structures. In 1 the guanine derivative acyclovir is coordinated to ruthenium through the N(7) atom, while in 2 the protonated guanine molecule is bound through the N(9) atom. Both complexes were also characterized by various physico-chemical methods in the solid state and in the solution. In vitro, the biological activity of 2 and of the previously described complexes [ mer-RuCl 3(acv)(DMSO-S)(CH 3OH)] · 0.5CH 3OH ( 3) and [ mer-RuCl 3(acv)(DMSO-S)(H 2O)] · H 2O ( 4) on tumour cells appear to be very similar to that of NAMI-A (NAMI-A=[ImH][ trans-RuCl 4(DMSO-S)Im]). All compounds are only weakly active on tumour cell proliferation but show an interesting proadhesive effect that suggest possible activity on tumour malignancy.