Solvent-Dependent Formation of Cd(II) Coordination Polymers Based on a C₂-Symmetric Tricarboxylate Linker

Three novel solvent-dependent Cd(II) coordination architectures [Cd 3 (BPT) 2 (DMF) 2 ]·2H 2 O [ 1 ], [Cd 3 (BPT) 2 (DMA) 2 ] [ 2 ], and [(CH 3 CH 2 ) 2 NH 2 ]·[Cd(BPT)]·2H 2 O [ 3 ] were obtained by the hydrothermal reaction of a C 2 -symmetric tricarboxylate linker, biphenyl-3,4′,5-tricarboxylic acid (H 3 BPT), with cadmium nitrate in the mixed solvents of water with N, N -dimethylformamide (DMF), N, N -dimethylacetamide (DMA), diethylformamide (DEF), respectively. Single-crystal X-ray diffraction analyses reveal that complex 1 is a three-dimensional (3D) network containing infinite Cd–O–Cd chains with the solvent DMF molecule bridging the neighboring Cd1 and Cd2 centers. Though complex 2 also has a 3D network containing infinite metal-carboxylate chains, the solvent DMA molecule only coordinates to one of the Cd(II) centers as a terminated solvent molecule. Complex 3 possesses a two-dimensional (2D) (6, 3) honeycomb type net formed by the mononuclear metal ion and the BPT ligand, which are further stacked in ABAB fashion through π–π interactions into a 3D supramolecular architecture. The effect of solvents on the formation of the coordination networks has been shown in the three compounds obtained, and the distinction of coordination architectures is due to the coordination abilities of solvent molecules with the metal centers. The structure stabilities and photoluminescent properties of the three coordination polymers have also been investigated.