Self-assembled Transition Metal Coordination Frameworks of ...

pg p_ g g _ Zinc(lI) & Cadmiumfll) complexes
interpreted as being caused by the replacement of enzymatic zinc by these metals.
Their complexes being more stable than those of zinc, they block the enzyme and
slow down the exchange of substrates. Therefore the study of Zn(II) and Cd(II)
complexation towards various environments have biological and pharmacological
interest. Conversely, there are reports of nonlinear optical materials exhibiting
efficient second harmonic generation (SHG) shown by Zn(Il) thiosemicarbazone
complexes [30], which are needed for many applications including high-density
optical recording, laser printing and optical measurement systems. In the light of these
kinds of applications in various fields including chemistry, biology and material
sciences and growing interest of new classes of materials, synthesis and
characterization of some novel Zn(lI) and Cd(lI) coordination compounds of
carbohydrazones and thiocarbohydrazones by self-assembly are also found useful.
6.2. Experimental
6.2.1. Materials
Zn(NO3)2- 6H2O (Merck), ZnBr2 (Reidel-De Haen), Zn(BF4)2- ZHZO
(Aldrich), Cd(NO3)2- 4H2O (Merck) and absolute ethanol (S.D.fine) were used as
received and solvents methanol (Ranchem), chloroform (S.D.fine), etc were purified
by standard procedures before use.
6.2.2. Synthesis of Zn (II) complexes
[Zn(H_;L2)Br2]2-H20 (24)
A solution of ZnBr2 (0.229 g, 1 mmol) in 10 ml of methanol was added to a
solution of HZLZ (0.220 g, 0.5 mmol) in l0 ml chloroform and refluxed for 1 h and
allowed to stand at room temperature. Yellow product separated out was filtered,
washed with methanol followed by ether and dried over P4010 in vacuo. Yield: 0.312
231