Dynamic scaffold of chiral binaphthol derivatives with the alkynylplatinum(II) terpyridine moiety

Platinum(II)-containing complexes with inherently chiral binaphthol derivatives display a versatile scaffold between random coils and single-turn helical strands, in which the conformational transition is controlled by the Pt center dot center dot center dot Pt and pi-pi interactions of alkynylplatinum( II) terpyridine moiety upon solvent and temperature modulation. The bisignate Cotton effect in the circular dichroism spectra is indicative of the cooperative transformation from random coil state to a compact single-turn M- or P- helix. More importantly, as revealed by the appearance of new UV-vis absorption and emission bands during conformational change, the self-assembly of the platinum(II)-containing complex into a helical structure is assisted by the metal center dot center dot center dot metal and pi-pi interactions of the alkynylplatinum(II) terpyridine moieties. The folded structure with stabilization via metal center dot center dot center dot metal and pi-pi interactions has been supported by density functional theory calculations, which provide insights into the folded geometry of these kind of metallo-foldamers.