Entropy Versus Enthalpy Controlled Temperature/Redox Dual‐Triggered Cages for Selective Anion Encapsulation and Release

Abstract

AbstractNew C3‐symmetric imidazole ligands were designed with phosphine and phosphine oxide linkers (LP and LPO, respectively) to demonstrate a dual‐triggered dynamic closed coordination cage. Both LP and LPO form discrete Zn4L4‐closed cages (1P and 1PO, respectively) with excellent selectively for BPh4−, whereas 1P and 1PO encapsulate neither a slightly larger size anion [B(C6H4CH3)4−] nor smaller size anions (BF4−, PF6−, SbF6−, and OSO2CF3−). 1PO exhibits more negative enthalpy and entropy changes upon anion encapsulation, thus releasing almost all of the encapsulated anions at high temperature (343 K) (trigger 1: BPh4−⊂1PO 1PO+BPh4−). In contrast 1P has less negative enthalpy and entropy changes, thus preserving the captured anion over a wide range of temperatures (298 K to 343 K). The 1P cage can be quantitatively oxidized to the 1PO cage by a mild oxidant (Ox.=H2O2), and therefore the captured anion can be released by a redox triggering event (trigger 2: BPh4−⊂1P+Ox.→1PO+BPh4−).