Nucleobase Stacking Sustained by Pt−Pt Interactions

Abstract

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.

N,C,N-Pincers in Platinum Bimetallic Complexes: Influence of the Pincer and Bridging Ligands on the Metal–Metal Bond and the Photophysical Properties

“…Therefore, these absorptions correspond to MMLCT transitions. Being characteristic of a Pt–Pt bond in bimetallic complexes, the energy increases as the metal–metal bond weakens. Unlike 9 and 10 , the calculated spectrum of 11 does not contain any transition showing pure MMLCT character, suggesting that 3.2949(2) Å is too long a distance to support a true Pt–Pt bonding.…”