Mono- and di-nuclear complexes of (trpy)MII (M = Pd, Pt) with the model nucleobase 1-methylcytosine.: Crystal structure and NMR solution studies

Reactions of (trpy)M-II (M = Pd and Pt; trpy = 2,2':6',2 "-terpyridine) with the model nucleobase 1-methylcytosine (Hmcyt) have been performed in water and studied by H-1 and Pt-195 NMR spectroscopy. Mononuclear [(trpy)M(Hmcyt-N-3)](2+) 1 (M = Pd) and 3 (M = Pt) and dinuclear [{(trpy)M}(2)(mcyt-N-3,N-4)](3+) 2 (M = Pd) and 4 (M = Pt) complexes are formed. The two (trpy)M entities in the dinuclear species 2 and 4 are arranged syn to each other in the solid state. X-Ray crystal structures have been performed for [(trpy)Pd(Hmcyt-N-3)][NO3](2). 5H(2)O 1, [{(trpy)Pd}(2)(mcyt-N-3,N-4)][ClO4](3). H2O 2b, [(trpy)Pt(Hmcyt-N-3)][NO3](2). 5H(2)O 3 and [{(trpy)Pt}(2)(mcyt-N-3,N-4)][ClO4](3). H2O 4b. The effect of the M-trpy entity on the resonances of the Hmcyt nucleobase in 1 and 3 (large downfield shifts of H-5 and H-6) is possibly related to the pi-acceptor capacity of the trpy ligand.