Studies on some oxovanadium(IV) complexes of acyl pyrazolone analogues

A series of novel bidentate pyrazolone based Schiff base ligands were synthesized by interaction of 4-benzoyl-3-methyl-1-(4′-methylphenyl)-2-pyrazolin-5-one with various aromatic amines like aniline, o-,m-,p-chloroaniline and o-,m-,p-toluidine in a ethanolic medium. All of these ligands have been characterized on the basis of elemental analysis, IR and 1H NMR data. The molecular geometries of five of these ligands have been determined by single crystal X-ray study. Crystallographic study reveals that these ligands exist in the amine-one tautomeric form in the solid state. NMR study also suggests the existence of the amine-one form in solution at room temperature. Ab initio calculations for representative ligand HL1 has been carried out to know the coordination site of the ligand. Novel vanadium Schiff base complexes of these ligands with general formula [OV(L1–7)2(H2O)] have been prepared by interaction of aqueous solution of vanadyl sulfate pentahydrate with DMF solution of the appropriate ligands. The resulting complexes have been characterized on the basis of elemental analysis, vanadium determination, molar conductance and magnetic measurements, thermo gravimetric analysis, infrared and electronic spectral studies. Suitable distorted octahedral structures have been proposed for these complexes.

Graphical abstractA series of bidentate ligands have been synthesized by condensation of 4-benzoyl-2,4-dihydro-5-methyl-2-(4′-methylphenyl)-3H-pyrazol-3-one with various aromatic amines. X-ray structure determination reveals that these ligands exist in the amine-one tautomeric form. With OV(IV), these ligands form distorted octahedral complexes, [OVL2(H2O)]; TGA, μeff, electronic spectral studies of which have been carried out. Ab initio calculations have been performed on one of the ligand.Figure optionsDownload full-size imageDownload as PowerPoint slide