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

New C -symmetric imidazole ligands were designed with phosphine and phosphine oxide linkers (L and L , respectively) to demonstrate a dual-triggered dynamic closed coordination cage. Both L and L form discrete Zn L -closed cages (1 and 1 , respectively) with excellent selectively for BPh , whereas 1 and 1 encapsulate neither a slightly larger size anion [B(C H CH ) ] nor smaller size anions (BF , PF , SbF , and OSO CF ). 1 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: BPh ⊂1 1 +BPh ). In contrast 1 has less negative enthalpy and entropy changes, thus preserving the captured anion over a wide range of temperatures (298 K to 343 K). The 1 cage can be quantitatively oxidized to the 1 cage by a mild oxidant (Ox.=H O ), and therefore the captured anion can be released by a redox triggering event (trigger 2: BPh ⊂1 +Ox.→1 +BPh ).