Thermal Analysis
The thermo gravimetric curves enable us to establish
information on thermal stability, amount confirmation and
purity of the compounds. Thus, thermal stability of the
ligand 4 and its Hg(II) complex was evaluated by thermal
analysis (TG/DTA). It was found that 4 undergo a two-step
thermal degradation (Figs. 11 and 12). The first step (150–
250 °C) could be attributed to the loss of the relative amino
groups of 4, while the second (325–420 °C) is due to the
cleavage of the calixarene backbone. As seen from TG
curve of Hg(II)-4 complex, it shows less stability than its
parent molecule as it shows 46% (1.258 mg) mass loss in
the first step (150–200 °C) whereas it was reduced to 31%
(0.34 mg) by wt at 300 °C in the second step. The DTA
result of the 4 showed the weight loss endothermic weight
loss endothermic peaks whereas 4-Hg(II) complex showed
surprisingly sharp weight loss exothermic peak temperature
of 180 °C, while others at 270, 400 and 458 °C in the
parent molecule becomes absent. The results indicated a
remarkable interaction between the amino groups of 4 and
the Hg(II). In general, the processing temperature limit of
Hg(II) complex of 4 is up to 150 °C.