Stereodirected Construction of Lemniscular Metallacycles via Linear d¹⁰ Ag^I/Au^I–NHC Coordination Engineering

Abstract

Helically twisted molecular architectures are critical motifs in both biology and synthetic supramolecular chemistry, with unique functional properties derived from their chiral geometries. Although lemniscular (figure-eight) macrocycles with a noncontact crossover point have attracted increasing interest, their metallosupramolecular analogs remain underexplored, largely because of synthetic challenges that hinder precise control. Herein, we report a coordination-driven strategy for the controlled construction of lemniscular metallacycles by exploiting the linear coordination geometry of Ag^I and Au^I complexes containing N-heterocyclic carbene (NHC) ligands. The key to this approach is the design of a bis-NHC imidazolium ligand containing helicene moieties, which promotes homochiral helicene dimerization and suppresses noncrossover macrocycle formation. Ag^I and Au^I–NHC lemniscular architectures were synthesized via this method, and the Au^I complex was validated through multiple synthetic pathways. The generated structures were characterized via electrospray ionization mass spectrometry, ultraviolet–visible absorption and fluorescence emission spectroscopy, X-ray crystallography, and density functional theory calculations, confirming the formation of the target metallacycles. Notably, this work addresses the long-standing scarcity of metallosupramolecular lemniscular systems, increases the structural diversity of macrocycles, and establishes a platform for the systematic investigation of the emergent functionalities of these complexes.

Keywords

Coordiantion-driven assembly / Coordination engineering / Helical structures / Metal-N-heterocyclic carbene / Metallosupramolecular lemniscular / Weak intermolecular interactions / Supramolecular chemistry / Metal ion / Ligand design / Nanostructures

RIGHTS & PERMISSIONS

2025 SIOC, CAS, Shanghai, & WILEY-VCH GmbH