A Helical Hydrogen-Bonded Aramide Macrocycle with a “Closed” Cavity: Dinuclear Ag(I) Coordination Assembly and Switchable Chirality Sensing

A helical aramide macrocycle, which features a “closed” cavity constrained by intramolecular hydrogen bonds with respect to an “open” cavity accessible to guest capture in its analogue, has been designed and synthesized. This macrocycle undergoes racemization via interconversion between its P- and M- helical conformations. Interestingly, a meso-dinuclear Ag(I)-bridged complex is formed upon mixing the macrocycle and AgSbF6 through a chirality self-sorting process. X-ray crystallographic analysis of the meso-dinuclear Ag(I) complex reveals that two Ag(I) cations are coordinated to the oriented amide carbonyl oxygen atoms, while the synergistic action of Ag−π interactions further stabilizes the dinuclear metal complex. Furthermore, the macrocycle demonstrates selective molecular recognition and chirality sensing for d/l-methionine methyl ester (d/l-Met) among the amino acid derivatives selected, enabling the determination of its absolute configuration and enantiomeric excess (ee) values. Notably, this chirality sensing can be switched by the formation and dissociation of the meso-dinuclear Ag(I) complex upon the addition and removal of Ag(I) cations. This work presents a coordination approach for manipulating chirality sensing and transfer through the assembly of a dinuclear metal complex.