Zinc Lab Report

1. Introduction
Zinc is an essential element required in the structure and function of many biomolecules [1]. The specific key roles of zinc in normal metabolic processes is because of some its uniqueness chemical features: unlike other abundant transition metals such as iron and copper it lacks redox activity, its complexes are kinetically labile and therefore the ligand exchange in complexes happen relatively rapid and co-ordination number of complexes may be readily change from four to five to six with the easy deformation of the geometry of the ligands in the co-ordination sphere and with more strongly acidity of low-co-ordination number. Zinc based compounds have also been used as potent antibacterial, antifungal, anticancer drugs and

The results show an agreement with the theoretical formulas suggested from the analytical data. Complexes 1-4 have good thermostability under 250 C. Complex 1 presents three mass loss stages. The first step in the range 323.29 to 350.37 C corresponds to the loss of the partial of thiosemicarbazone by the breakdown of NN bond. Based on the DSC curve, there is a little exothermic signal (Tp = 329.69 C, H = -214.07 Jg-1). The second and third stage occurs in the range 419.51-509.02 C and 540.84-567.93 C with two successive exothermic peaks (Tp = 467.61 C, H = -2512.25 Jg-1; Tp = 557.04 C, H = -4754.31 Jg-1) on the DSC curve which are consistent with the loss of imidazole and the rest of TSC ligand. The value 19.08 % of the final residue is consistent with the theoretical percentage 18.0 % of the ZnO. Complex 2 showed a weight loss less than 80 C related to the evaporation of surface solvent. This complex has also three decomposition steps. According to the DSC curve a small exothermic peak appears in the first stage (330.80-350.17C, Tp =344.46C, H = -88.80 Jg-1) and corresponds to the loss of the bipy molecule. This step was immediately and slightly overlapping followed by the loss of PhNH from thiosemicarbazone (calc.: 17.0 and exp.: 17.1 %). Then, in the third stage between 430.11 and 536.50 C, the rest of TSC was lost with an exothermic signal in DSC curve (Tp = 492.40 C, H = -4540.28 Jg-1). Finally residue at 1000C is metal thiosyanate (calc.: 22.8 and exp.: 23.33 %) as an intermediate which expected to result ZnS at higher temperatures [34, 35]. Decomposition of complex 3 begins from 263.48C and the TGA graph involves overlapping steps. According to DSC, thiosemicarbazone and MeImd moiety were eliminated through one small endothermic (Tp = 290.19 C, H = 150.18 Jg-1) and two exothermic steps (Tp = 481.93 C, H = -1201.90 Jg-1; Tp =