Stable Luminescent [Cu(NN)(PP)](+) Complexes Incorporating a β‐Cyclodextrin‐Based Diphosphane Ligand with Metal‐Confining Properties

A β‐cyclodextrin‐based diphosphane with metal‐confining properties was efficiently synthesized thanks to an unprecedented Smiles‐like rearrangement of diphenyl‐(2‐phosphanylphenyl)phosphane in the presence of excess n‐BuLi. The cis‐chelating bidentate ligand is capable of forming very stable heteroleptic [Cu(NN)(PP)](+) complexes in which a metal‐bound diimine ligand (bpy, phen, or mmp) is located within the cyclodextrin cavity. As a result of ligand encapsulation, flattening of the metal tetrahedral geometry in the excited state is disfavored, thereby resulting in enhanced luminescent properties.