Coordination capacity of cytosine, adenine and derivatives towards open-paddlewheel diruthenium compounds

Abstract

[Ru2Cl2(DPhF)3] (DPhF = diphenylformamidinate) links preferentially to the junctions of RNA (ribonucleic acid) structures, although the bonding mode is not known. In order to clarify this question the reactions between [Ru2Cl2(DPhF)3] and cytosine (Hcyto), cytidine (Hcyti), cytidine 2′,3′-cyclic monophosphate sodium salt (NacCMP), adenine (Hade), adenosine (Haden) and adenosine 3′,5′-cyclic monophosphate (HcAMP) have been carried out. In the resultant complexes, cyto (cytosinate), cyti (cytidinate), cCMP (cytidine 2′,3′-cyclic monophosphate monoanion), ade (adeninate), aden (adenosinate) and cAMP (deprotonated adenosine 3′,5′-cyclic monophosphate) are bonded to the diruthenium unit as N,N′-bridging ligands, as confirmed by the solution of the crystal structures of [RuCl(DPhF)3(cyto)] and [RuCl(DPhF)3(ade)] by X-ray diffraction. The axial positions of the diruthenium species are still available for additional interactions with other residues that could explain its preference towards RNA junctions.