Rational Design of Multi-Stimuli-Responsive Scaffolds: Synthesis of Luminescent Oligo(ethynylpyridine)-Containing Alkynylplatinum(II) Polypyridine Foldamers Stabilized by Pt•••Pt Interactions

A series of oligo(ethynylpyridine)-containing alkynylplatinum(II) terpyridine/bzimpy (bzimpy = 2,6-bis(N-alkylbenzimidazol-2'-yl)pyridine) metallofoldamers has been designed and synthesized to investigate the potential applications of metallofoldamers imparted by the rich spectroscopic responses of Pt center dot center dot center dot Pt interactions. Apart from the control of the folding/unfolding processes by solvent compositions and temperatures, this class of metallofoldamers has also been found to exhibit reversible folding/unfolding behaviors mediated by the addition of acids/bases due to the incorporation of the acid-sensitive oligo(ethynylpyridine) derivatives. More importantly, the intramolecular Pt center dot center dot center dot Pt interaction has been found to play a crucial role in governing the folded state conformation. The conformation of this class of metallofoldamers has been investigated by 2D ROESY NMR, electronic absorption, and emission spectroscopy, which provide further insights into the rational molecular design and multidimensional control of metallofoldamers upon the application of various external stimuli, leading to the preparation of multi-stimuli-responsive materials for potential applications in material sciences.