Synthesis, spectral, thermal and crystallographic investigations on oxovanadium(IV) and manganese(III) complexes derived from heterocyclic β-diketone and 2-amino ethanol

Abstract

Novel mononuclear oxovanadium(IV) and manganese(III) complexes [VO(L1)2·H2O] (1); [VO(L2)2·H2O] (2); [VO(L3)2·H2O] (3); [Mn(L1)2]ClO4·H2O (4); [Mn(L2)2] ClO4·H2O (5); [Mn(L3)2]ClO4·H2O (6) were prepared by condensation of 1 mol of VOSO4·5H2O or Mn(OAc)3· 2H2O with 2 mol of ligand HL1, HL2 or HL3 (where HL1 = 4-[(2-hydroxy-ethylamino)-methylene]-5-methyl-2- phenyl-2,4-dihydro-pyrazol-3-one; HL2=4-[(2-hydroxy-ethylamino)-methylene]-5-methyl-2-p-tolyl-2,4-dihydro-pyrazol-3-one; HL3=4-{4-[(2-hydroxy-ethyl-amino)-methyl]-3-methyl-5-oxo-4,5-dihydropyrazol-1-yl} benzene sulfonic acid). The resulting complexes were characterized by elemental analyses, molar conductance, magnetic and decomposition temperature measurements, electron spin resonance, FAB mass, IR and electronic spectral studies. From TGA, DTA and DSC, the thermal behaviour and degradation kinetic were studied. Electronic spectra and magnetic susceptibility measurements indicate distorted octahedral stereochemistry of oxovanadium(IV) complexes and regular octahedral stereochemistry of manganese(III) complexes. Hamiltonian and bonding parameters found from ESR spectra indicate the metal ligand bonding is partial covalent. The X-ray single crystal determination of one of the representative ligand was carried out which suggests existence of amine-one tautomeric form in the solid state. The 1H-NMR spectra support the existence of imine-ol form in solution state. The LC-MS studies sustain the1H-NMR result. The electronic structure of the same representative ligand was optimized using 6-311G basis set at HF level ab initio studies to predict the coordinating atoms of the ligand.