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

Abstract

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.