Synthesis and characterisation of manganese(III) heterochelates

Manganese(III) complexes of the type: (i) [Mn(Sal-o-phen)Bzp].2H(2)O, (ii) [Mn(Bzp-o-phen)Sal].2H(2)O, (iii) [Mn(Acp-en) 1, 10 phen]ClO4 and (iv) [Mn(Acp-en) 2, 2' dipy]ClO4 (where, Sal-o-phen and Bzp-o-phen are the Schiff bases derived from salicylaldehyde and 1-phenyl-3-methyl-4-benzoyl-2-pyrazoline-5-one and o-phenylenediamine respectively; Acp-ethylene is a Schiff base derived from 1-phenyl-3-methyl-4-acetyl-2-pyrazoline-5-one and ethylenediamine; 1, 10 phen = 1, 10 phenanthroline and 2, 2' dipy = 2, 2' dipyridyl) have been prepared and their physico-chemical properties studied. The former two complexes are non-electrolytes and the later two are 1: 1 electrolytes in solution. Magnetic moment values close to 4.9 B.M. indicate the presence of Mn(III) complexes with four unpaired electrons and lack of any kind of exchange interaction. On the basis of analytical and physical data a tetragonally distorted octahedral structure is suggested for all of the complexes. The complexes were treated for TGA and DTA studies. From the TGA curves, thermo-kinetic parameters such as activation energy (E), order of reaction (n), pre-exponential factor (A) and entropy change (AS) have been calculated using different methods suggested by Horowitz-Metzger, Freeman-Carroll, Coats-Redfern and Sharp-Wentworth.