An Organometallic [2]Catenane With Pt‒(di‐NHC)‒Pt Units: A Topology‐Driven Strategy for Enhanced Phosphorescence in Discrete Aggregates

Mechanically interlocked molecules (MIMs) can be conceptualized as a distinct class of discrete and soluble aggregates, where the mechanical bond restricts selected intramolecular motions, thereby triggering emission enhancement analogous to aggregation-induced emission (AIE). Herein, we present phosphorescent MIMs based on a benzobiscarbene bridged dinuclear Pt^II complex (NHC = N-heterocyclic carbene ligand). Tailoring the N-substituents of the benzobiscarbene ligand allowed selective access to the syn-configured dinuclear complex syn-[Pt₂(1b)X₂] (X = I, OTf). Self-assembly of syn-[Pt₂(1b)(OTf)₂] with bipyridyl ligands L² and L³ yielded two discrete MIMs: the Borromean rings [2-BRs](OTf)₁₂ stabilized by π···π interactions and the [2]catenane [3b-IL](OTf)₄, generated and stabilized by solvophobic effects. While the π···π interactions in the Borromean rings lead to severe phosphorescence quenching, the solvophobically assembled [2]catenane effectively circumvents such quenching, while simultaneously restricting intramolecular rotations and vibrations. Consequently, the [2]catenane displays a drastic phosphorescence enhancement compared to the Borromean rings.