meta -Carborane-Based Macrocyclic Arenes: Synthesis and Inner-Wall Modification

Abstract

Precise inner-wall modification of macrocyclic arenes remains a formidable challenge in supramolecular chemistry due to the scarcity of available synthetic strategies. Herein, we report the design and synthesis of a novel meta-carborane-based macrocyclic arene featuring a rigid triangular prismatic cavity. By finely tuning the stoichiometry of tetrabutylammonium fluoride (TBAF), we achieved the first stepwise inner-wall functionalization of this macrocyclic system via the controllable deboronation of closo-meta-carborane units, selectively affording mono-, bis-, and tris-nido-carborane-modified products in high isolated yields. This approach enables programmable modulation of the cavity electrostatic microenvironment under mild conditions with high site selectivity. In addition, a metal-free oxidative B–N coupling reaction was employed to achieve inner-wall postmodification. Notably, covalent attachment of fluorophores to the macrocyclic scaffold leads to a significant enhancement of emission intensity, which is tentatively attributed to the restriction of intramolecular motions (RIM) imposed by the macrocyclic framework. This work establishes a new paradigm for the inner-wall engineering of macrocyclic arenes and substantially broadens the application horizons of carborane-based supramolecular chemistry.