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 (H2L) was reacted with transition metal ions to yield the complexes of the composition ML [where M = Co (II), Ni (II), Cu (II), & Zn (II)]. The copper based compound 3 (IC50 = 5.857 mu M) showed activities even higher than the standard drug. TG and DTA analyses under static air in the temperature range 30-1000 degrees 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-Cu*>E-Co*>E-Ni*>E-Zn*, respectively.