Rotaxane Pt(II)-complexes: mechanical bonding for chemically robust luminophores and stimuli responsive behaviour

We report an approach to rotaxanes in which the metal ion of a cyclometallated Pt(II) luminophore is embedded in the space created by the mechanical bond. Our results show that the interlocked ligand environment stabilises a normally labile Pt(II)–triazole bond against displacement by competing ligands and that the crowded environment of the mechanical bond retards oxidation of the Pt(II) centre, without perturbing the photophysical properties of the complex. When an additional pyridyl binding site is included in the axle, the luminescence of the Pt(II) centre is quenched, an effect that can be selectively reversed by the binding of Ag(I). Our results suggest that readily available interlocked metal-based phosphors can be designed to be stimuli responsive and have advantages as stabilised triplet harvesting dopants for device applications.