Hydrothermal syntheses and characterization of a series of luminescent Cd(ii) frameworks with pyridine-based and benzene-based bis-triazole ligands

Abstract

Using the pyridine-based and benzene-based bis-triazole ligands 2,6-di-(1,2,4-triazole-4-yl)pyridine (L1) and 1,4-di-(1,2,4-triazole-4-yl) benzene (L2), a series of luminescent Cd(II) coordination polymers, namely, [Cd(μ2-L1)2I2]n (1), {[Cd3(μ3-L1)6](BF4)5(PF6)·18H2O}n (2), [Cd(μ2-L2)I2]n (3), [Cd(μ2-L2)(μ1,3-NCS)2]n (4), {[Cd(μ2-L2)(L2)(H2O)3]SiF6·3H2O}n (5), {[Cd(μ2-L2)(L2)(H2O)3]SiF6·CH3OH·2.5H2O}n (6), {[Cd(μ2-L2)3](BF4)2}n (7) and {[Cd(μ2-L2)3](ClO4)2}n (8), have been isolated. 1 represents a novel 2D framework containing 1D infinite right- and left-handed helical chains. 2 is a 3D coordination framework based on trinuclear Cd(II) clusters containing triangular channels, in which eighteen free water molecules, five free BF4− and one free PF6− anions are located. For 3, the L2 ligands can bridge CdII centers forming a 1D chain, while for 4 the L2 and μ1,3-NCS− co-ligands can further bridge CdII centers forming a 2D corrugated layer. 5 and 6 represent a novel coordination framework containing 1D rhombic nano-porous channels, in which free SiF62− anions and free solvent molecules are located. 7 and 8 also represent a novel coordination framework containing another kind of trianglular nano-porous channel, in which free BF4− or ClO4− anions are located. Solid-state fluorescent spectra of 1–8 have been determined indicating strong fluorescent emission bands. The result also reveals that L1 and L2 can adopt versatile coordination modes and have great potential in the construction of these highly-dimensional luminescent coordination frameworks.