C3i-Symmetric Octanuclear Cadmium Cages: Double-Anion-Templated Synthesis, Formation Mechanism, and Properties

A series of C3i-symmetric bicapped trigonal antiprismatic Cd8 cages [2X@Cd8L6(H2O)6].n?Y.solvents (X=Cl-, Y=NO3-, n=2: MOCC-4; X=Br-, Y=NO3-, n=2: MOCC-5; X=NO3-, Y=NO3-, n=2: MOCC-6; X=NO3-, Y=BF4-, n=2: MOCC-7; X=NO3-, Y=ClO4-, n=2: MOCC-8; X=CO32-, n=0: MOCC-9), doubly anion templated by different anions, were solvothermally synthesized by means of a flexible ligand. Interestingly, the CO32- template for MOCC-9 was generated in situ by two-step decomposition of DMF solvent. For other MOCCs, spherical or trigonal monovalent anions could also play the role of template in their formation. The template abilities of these anions in the formation of the cages were experimentally studied and are discussed for the first time. Anion exchange of MOCC-8 was carried out and showed anion-size selectivity. All of the cage-like compounds emit strong luminescence at room temperature.