Synthesis and Characterization of Four Novel Supramolecular Compounds Based on Metal Zinc and Cadmium

Four zinc(II) or cadmium(II) supramolecular compounds, namely, [Zn(ox)(Him)]n (1), [Zn(bta)2]n (2),
[Zn(H2O)4(na)2]n (3), and [Cd2(ox)(OH)2]n (4) (ox = oxalate anion, Him = imidazole, bta = benzotriazole anion, and
na = nicotinic anion), have been synthesized. Among them, 1 is constructed to be a 3-D supramolecular framework
by covalent and noncovalent interactions, 2 containing two bta coordination modes displays a 2-D layer structure
linked by covalent bonds, the 3-D network of 3 is mainly constructed by strong hydrogen bonds, while 4 exhibits a
3-D framework with 1-D channels only constructed by covalent interactions. The different metal centers and ligand
dimensions result in the different structures although they were obtained from similar reaction systems. All of
these compounds display strong fluorescence emissions in the blue region, which may be assigned to charge transfer
between metal and ligand (for 1, 3, and 4) and the π → π* transition of bta (for 2).