Anion- and Conjugated Building Block-Driven Construction of Handcuffs and Cages, Featuring In Situ Topological Transformation from Handcuff to Double-Z Cage

A flexible tetradentate ligand, L,1,2,4,5-tetrakis((pyridin-4-ylthio)methyl)benzene, was designed to precisely construct topologically distinct handcuff-shaped molecules 1, 2 and Double-Z cage 1 through coordination-driven self-assembly with building blocks ( B1 – B3 ). In particular, the size of the conjugated surfaces of B1 – B3 and hydrogen bond-accepting properties of anions play critical roles in influencing the resulting topology, as supported by single-crystal X-ray diffraction (SCXRD), electrostatic potential (ESP), and independent gradient model (IGM) calculations. BF 4 – anions favored the formation of handcuff-shaped structures with smaller conjugated building blocks B1 and B2, while Double-Z Cage 1 with a larger conjugated building block B3 . Intriguingly, when BF 4 – is replaced with OTf –, the stronger electron-donating and hydrogen bond-accepting capabilities of OTf – induce a topological transformation from Handcuff 2 to Double-Z Cage 3 . Specifically, Handcuff 1 and Double-Z Cage 1 correspond to Handcuff 3 and Double-Z Cage 2, respectively, demonstrating how anion identity influences the final topology for similar building blocks. Furthermore, a remarkable in situ topological transformation from Handcuff 2 to Double-Z Cage 3 was achieved under mild conditions with the addition of KOTf to Handcuff 2, as confirmed by real-time 1 H NMR monitoring. This work offers promising avenues for designing responsive molecular materials with tailored topologies.