Abstract
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-[Pt(2)(1b)X(2)] (X = I, OTf). Self-assembly of syn-[Pt(2)(1b)(OTf)(2)] with bipyridyl ligands L(2) and L(3) 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.