Chiral macrocycles forming high-affinity host-guest homoternary complexes for chiral discrimination and amplified circularly polarized luminescence

The development of macrocyclic hosts with high-affinity 1:2 recognition capabilities is crucial for advancing supramolecular chemistry and its applications. While cucurbit[8]uril (CB[8]) has long been recognized for its unparallel 1:2 binding affinity, its limitations-including poor solubility, difficulty to modify and lack of optical activity-have hindered broader utilization. Here, we introduce a class of enantiopure chiral macrocycles, RRRR- or SSSS-corral[4]BINOL (C[4]Bs), which exhibit remarkable 1:2 recognition properties in water that are comparable or even surpass CB[8]. Using UV-Vis, fluorometric, and isothermal titration calorimetry (ITC), we demonstrate that C[4]Bs form stable homoternary complexes with 11 singly positively charged planar aromatic guests, with binding affinities up to 10¹⁷M^-2. These ultrahigh affinities make C[4]Bs versatile alternatives to CB[8], offering advantages such as superior water-solubility, ease of structural modification, and strong fluorescence. Furthermore, the unique chiral nature of C[4]Bs enables efficient fluorescent discrimination of chiral substrates and chirality transfer to non-chiral dyes, resulting in strong circularly polarized luminescence (CPL) with |g_lum | values up to 1.1 ×10^-2. This study establishes C[4]Bs not only as powerful hosts for aqueous-phase supramolecular complexation but also as a promising platform for developing chiral functional materials.