Syntheses, structures, and characterization of a series of novel zinc(II) and cadmium(II) compounds based on 2,6-di-(1,2,4-triazole-4-yl)pyridine

Using a pyridine-based bi-triazole ligand 2,6-di-(1,2,4-triazole-4-yl)pyridine (L), we have synthesized four novel Zn(II)/Cd(II) coordination polymers, namely, {[Zn3L4(NCS)(6)]center dot 2CH(3)OH center dot H2O}(n) (1), [CdL2(NCS)(2)](n) (2), [CdL2(NO3)(2)](n) (3), and {[CdL(mu-ox)(H2O)]center dot 2H(2)O}(n) (4) (ox = oxalate anion). 1 is the first triazole-zinc(II) compound simultaneously comprising four- and six-coordinate zinc(II) centers. Weak C-H center dot center dot center dot N and C-H center dot center dot center dot S interactions assembled 1D chains of 1 into a 3D supramolecular network, in which 1D hydrophilic channels encapsulating guest water and methanol molecules can be found. 2 contains a 1D double-stranded chain using CdL2(NCS)(2) as repeating unit. 3 is a 2D polymer with chiral group P2(1)2(1)2(1), indicating achiral ligand L and metal centers can be used as building blocks to construct chiral crystals. For 4, Cd(II) centers are linked via a bis(bidentate) oxalate anion to form 1D zigzag chains; furthermore, lattice water molecules act as hydrogen-bonding nodes to extend 4 into a 2D layer structure through strong O center dot center dot center dot O hydrogen synthons. Intensive solid-state fluorescence spectra of 1-4 have been determined.