Assimilating an Enantiopure Supramolecular Nanocage from Achi-ral Building Blocks: The Impact of Chiral Recognition and Spin-crossover

Chiral recognition and discrimination are not only of significance in nature’s intricate biochemical processes but also, at the supramolecular level, have proved to aid the understanding and exploration of chirality and their effects in sensing, molecular separation, and so on. Herein, we discuss the coordination-driven self-assembly to fabricate an enantioselective tetra-hedral nanocage with a general formula MII4L4 (MOC-1, M = Zn, Fe) starting from achiral building blocks. Systematic employment of tris-(4-aminophenyl)triazine (TzTa) with hydrogen bonding acceptor sites as triazine core and 2-butyl-5-chloro-imidazole-4-carboxaldehyde results in a racemic mixture of two enantiomeric cages (Td1), while the absence of such chirality directing groups (Td0), or hydrogen bonding acceptor sites (Td2) assimilates as a dynamic mixture of multiple stereoisomers. Interestingly, the compelling interplay of hydrogen bonding presented by R- or S-Binol as a chiral bias during the subcomponent self-assembly of Td1 induced the selective formation of a single enan-tiopure cage MOC-1Zn(R/S) via “reverse chiral recognition”, where the ultimate stereochemistry of the cage is deter-mined by the guest (Binol). Furthermore, subsequent replacement of the ZnII vertices of MOC-1Zn(R/S) by FeII ions al-lows the straightforward imprinting of a given stereochemistry in MOC-1Fe(R/S), unlike the racemization occurred by the subcomponent self-assembly (Fe4AS). The effective stereochemical coupling between the Binol and enantiopure MOC-1Fe(R/S) dictates the effective spin-state stabilization of the host and, thus, their magnetic responses. This exciting feature opens a new paradigm to associate the spin-crossover phenomenon with supramolecular chirality.