Nucleobase Stacking Sustained by Pt−Pt Interactions

This article reports the use of metal–metal interactions as a way to induce nucleobase stacking in a dinucleotide chain. We synthetized and study a series of C,N-cyclometallated platinum(II) binuclear complexes derived from 6-phenylpurine dinucleotide 1 as proligand, and β-diketonates, 2,2'-bipyridines and 1,10-phenanthroline as ancillary ligands. The X-ray diffraction analysis revealed that the diketonate derivatives 7 and 8 are chiral helixes sustained by Pt−Pt intramolecular interactions that allow the nucleobase stacking. The folded helical structures are maintained in solution, as demonstrated by the appearance of metal–metal-to-ligand charge-transfer (MMLCT) transitions in the UV-vis spectra. The influence of the ancillary ligand in the molecular structure was evidenced by the absence of bands derived from M−M interactions in the absorption spectra of 2,2’-bipyridine and and 1,10-phenanthroline derivatives 12–14. The existence of Pt−Pt in the complexes of this study can be also detected by electrochemistry.