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

Abstract

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 ¹H and ¹⁹⁵Pt 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]₂·5H₂O 1, [{(trpy)Pd}₂(mcyt-N ³,N ⁴)][ClO₄]₃·H₂O 2b, [(trpy)Pt(Hmcyt-N ³)][NO₃]₂·5H₂O 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 H⁵ and H⁶) is possibly related to the π-acceptor capacity of the trpy ligand.