Activity on Leishmania tropica of Metal Complexes with NNOO Tetradentate Schiff Base Ligand: Kinetic and Thermodynamic Studies from TG-DTA Analysis

In the search for antileishmanial drug, tetradentate Schiff base ligand 2-((E)-((2-(((Z)-(2-hydroxyphenyl)methylidene)amino)phenyl)imino)methyl) phenol (H/sub 2/L) was reacted with transition metal ions to yield the complexes of the composition ML (where M = Co (II), Ni (II), Cu (II), and Zn (II)). The copper based compound 3 (IC/sub 50/ = 5.857 meu M) showed activities even higher than the standard drug. TG and DTA analyses under static air in the temperature range 30-1000 degree C were also observed for all the compounds. The TG-DTA analyses and the subsequent themodynamic and kinetic parameters calculated using the TG-DTA curves, have potential relevance for the biological activities. Horowitz-Metzger method was applied for calculating the activation energies and order of pyrolysis. Thermodynamic parameters like delta S*, delta H* and delta G* were subsequently calculated using the corresponding expressions. The order of decreasing thermal stability and decreasing activation energy follow the orders Ni(II) >Co(II)>Zn(II) >Cu(II) and E*/sub Cu/ E*/sub Co/ E*/sub Ni/ E*/sub Zn/, respectively. (author)