Solution structure and behaviour of delta-cis-alpha-[Ru(R,R-picchxnMe2)(phi)]2+ by NMR spectroscopy and molecular modelling

The self-association of the DNA metalloprobe delta-cis-alpha-[Ru(R,R-picchxnMe2)(phi)]2+(-phi) in aqueous solution has been investigated using 1H NMR spectroscopy and molecular modelling. The concentration dependence of proton chemical shifts of the complex gave initial indications of a selfassociated species, while its structural isomer delta-cis-alpha-[Ru(R,R-picchxnMe2)(phi)]2+(-phi) showed no such dependence. 2D-COSY and 2D-ROESY experiments were used for the complete assignment of the proton resonances of both isomers and allowed a qualitative determination of the selfassociation of the isomer through the detection of intermolecular ROEs. NMR spectroscopy can also be effectively used to differentiate - and diastereomers. In addition, we show, by pulsed field gradient longitudinal eddy-current delay (PFGLED) NMR spectroscopy, that -phi selfassociates at higher concentrations with an effective molecular weight at 25 mM three times that at 2.5 mM. This apparent oligomerisation was not observed for the -isomer.