Synthesis, spectral, thermal and coordination aspects of pentadentate Schiff-base complexes of the type [Mn(L)(X)] Á H 2 O [where H 2 L ¼ N,N 0 -diethylamine bis(1-phenyl-3-methyl-4-acetylimino-2-pyrazoline-5-ol) and X¼NCS, NO 3 , ClO 4 , CN or N 3 ] are reported. The Schiffbase ligand (H 2 L) and metal complexes have been characterized by elemental analysis, FT-IR, 1 H-NMR, magnetic measurements, molar conductivity measurements, electronic spectra, cyclic voltammetric and thermal studies. Magnetic moment values are close to 4.9 B.M. indicating high spin complexes lacking exchange interaction. Infrared spectral data suggest coordination of the secondary amino group making the ligand pentadentate. All complexes are electrochemically inactive, indicating high stability. Thermal decomposition of the Schiff-base complexes indicates loss of water of hydration and decomposition of the ligand. Kinetic parameters such as order of reaction (n) and the energy of activation (E a ) are reported using the Horowitz-Metzger method, indicating first order kinetics and giving the activation entropy (ÁS*), the activation enthalpy (ÁH*) and the free energy of activation (ÁG*).

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