Selective π‑Metalation of Nut[6]Arene With Large and Chiral Cavity for Recognition Toward Bulky Anions in Water

Abstract

ABSTRACT Selective π‐metalation of macrocyclic arenes (MAs) featuring large and stable chiral cavities remains a considerable challenge. Consequently, the recognition of the π‐metalated MAs toward bulky anions, especially organic and chiral anions, is attractive but remains unexplored. In this work, a new macrocyclic arene named nut[6]arene ( NA ) was reported, which showed a rigid hexagonal structure and stable chiral cavity. Starting from NA , a series of π‐metalated MAs were selectively synthesized. In particular, exo ‐tri‐metalated NA ( NA‐3Ru‐I ) with a C 3 symmetrical structure was selectively obtained in high yields by the modulation of ligand sterics, molar ratio, and reaction temperature, which showed a large and electron‐deficient cavity. Consequently, water‐soluble NA‐3Ru‐II could effectively bind large inorganic anions, including ReO 4 − and PF 6 − to form 1:1 stable host‐guest complexes. Especially, NA‐3Ru‐II showed strong binding abilities toward various organic sulfonate anions and carboxylate anions. Moreover, a pair of enantiomeric NA‐3Ru‐II was also obtained, and they exhibited enantioselective recognitions for chiral anionic guests in aqueous solution, providing a new chiral platform for anion recognition.