Cd(II)-Coordination Framework: Synthesis, Anion-Induced Structural Transformation, Anion-Responsive Luminescence, and Anion Separation

A series of Cd(II) coordination frameworks that are constructed from a new oxadiazole-bridged ligand 3,5-bis(3-pyridy1-3-(3 '-methylpheny1)-1,3,4-oxadiazole (L) and CdX2 (X = NO3(-), Cl-, Br-, I-, N-3(-,) and SCN-) were synthesized. The NO3- anion of the solid CdL2(NO3)(2).2THF (1) is able to be quantitatively exchanged with Cl-, Br-, I-, SCN-, and N-3(-) in the solid state. For Cl- and Br-, the anion exchange resulted in a anion-induced structural transformation to form the structures of 2 and 3, respectively. In addition, the Cd(II) structure herein exhibits the anion-responsive photoluminescence, which could be a useful method to monitor the anion-exchange process. Notably, compound 1 can recognize and completely separate SCN-/N-3(-) with similar geometry.