Hydrothermal Syntheses, Crystal Structures, and Characteristics of a Series of Cd−btx Coordination Polymers (btx = 1,4-Bis(triazol-1-ylmethyl)benzene)

Four novel cadmium−btx (btx = 1,4-bis(triazol-1-ylmethyl)benzene) coordination polymers [Cd(btx)2(NO3)2]n (1),
[Cd(btx)2Cl2]n (2), [Cd(btx)(SO4)(H2O)2]n (3), and [Cd(btx)(S2O7)(H2O)]n (4) have been prepared by hydrothermal
reaction (140 or 180 °C) and characterized. Both 1 and 2 have two-dimensional rhombohedral grid structures, 3
possesses a two-dimensional rectangular grid structure, and 4 displays a three-dimensional framework, which is
formed by btx bridging parallel layers. To the author's best knowledge, polymer 4 is the first Cd(II) polymer in
which the Cd(II) ion is eight-coordinated in a hexagonal bipyrimidal geometry. In addition, we studied the effects
of temperature on the hydrothermal reaction system of btx and CdSO4 and found that different products can be
obtained at different temperatures. Furthermore, polymer 3 possesses a very strong third-order NLO absorptive
effect with an α2 value of 1.15 × 10-9 m W-1. Polymers 2−4 display strong fluorescent emissions in the solid state
at room temperature. The DTA and TGA results of the four polymers are in agreement with the crystal structures.