Synthesis and characterization of a new thiohydrazone ligand, 3-carboxy-2-hydroxybenzaldehydemorpholine N-thiohydrazone and its metal complexes

Abstract

The reaction of 3-formylsalicylic acid with morpholine N-thiohydrazide in ethanol leading to the formation of a new thiohydrazone, 3-carboxy-2-hydroxybenzaldehydemorpholine N-thiohydrazone (H2chbmth) is described. This thiohydrazone ligand remained as the thio-keto form in the solid state. However, thioketo- and a small amount of the thiol-tautomeric forms (H2chbmth and H3chbmthol, respectively) remain in equilibrium in solution. The reactions of the ligand with different metal salts (in 1 : 1 molar ratio) leading to the synthesis of many new metal complexes have been studied. Depending on pH of the reaction medium and the nature of the metal salt used, the ligand is found to be monobasic tridentate, dibasic tridentate, monobasic bidentate or neutral bidentate giving complexes [Co(H2chbmth)2]X2, [X = NO3 (11), ½SO4 (13)]; [Cd(H2chbmth)(H2O)2]SO4 (21); [M(Hchbmth)X], [M = Cu(II) and X = Cl (1), NO3 (2), CH3COO (4); M = Ni(II) and X = Cl (6), NO3 (7); M = Co(II) and X = NO3 (12), CH3COO (14); M = Zn and X = Cl (17), CH3COO (18); M = Hg(II) and X = Cl (23), CH3COO (24)]; [Ni(H2chbmthol)(acac)] (9); [Co(Hchbmth)Cl]·2H2O (10), [Cu(Hchbmth)H2O]½SO4 (3); [Cu(Hchbmthol)]2 (5); [M(Hchbmthol)X], [M = Ni(II) and X = H2O (8); M = VO(II) and X = H2O (15); M = Pd(II) and X = H2O (16); M = Zn(II) and X = NH3 (19); M = Cd(II) and X = H2O (20), NH3 (22); M = Hg(II) and X = NH3 (25)]. In situ reactions of metal salts with the ligand components (i.e. 3-formylsalicylic acid and morpholine N-thiohydrazide) in ethanol resulted the same complexes. The complexes are characterized by elemental analyses, magnetic susceptibilities, molar conductances, molecular weights and spectroscopic (IR, ESR, 1H NMR and UV-visible) data.