We have synthesized a novel series of Schiff bases by condensation of 4-aminoantipyrine and various aromatic aldehydes followed by reaction with thiosemicarbazide. These thiosemicarbazones are potential ligands toward transition metal ions. The reaction of copper(II) salts with 4[N-(benzalidene)amino]antipyrinethiosemicarbazone (BAAPTS), 4[N-(4′-methoxybenzalidene) amino] antipyrinethiosemicarbozone (MBAAPTS), 4[N-(4′-dimethylamino benzalidene) amino] antipyrinethiosemicarbazone (DABAAPTS), and 4[N-(cinnamalidene) amino] antipyrinethiosemicarbazone (CAAPTS) resulted in the formation of solid complexes with the general composition CuX2 · (H2O)(L)(X = Cl, Br,NO3,NCS, or CH3COO; L = BAAPTS, MBAAPTS, DABAAPTS, or CAAPTS). These complexes were characterized through elemental analysis, molecular weight, electrical conductance, infrared, electronic spectra, and magnetic susceptibilities at room temperature. Copper(II) complexes with BAAPTS and MBAAPTS were screened for antibacterial and antifungal properties and have exhibited potential activity. Thermal stabilities of two representative complexes were also investigated.

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Synthesis, Spectral, and Biological Properties of Copper(II) Complexes of Thiosemicarbazones of Schiff Bases Derived from 4-Aminoantipyrine and Aromatic Aldehydes

Neutral complexes of Cu(II), Ni(II), Co(II), Mn(II), VO(IV) and Zn(II) have been synthesised from the Schiff bases derived from salicylidene-4-aminoantipyrine and 2-aminophenol/2-aminothiophenol. The structural features have been arrived at from their microanalytical, IR, UV-Vis., 1H NMR and ESR spectral data. All of the complexes exhibit square-planar geometry except the Mn(II) and VO(IV) complexes. The Mn(II) chelates show an octahedral environment and the VO(IV) chelates exist in a square-pyramidal geometry. The non-electrolytic and monomeric nature of the complexes are evidenced by their magnetic susceptibility and low conductance data. The electrochemical behaviour of the Cu(II), Mn(II) and VO(IV) complexes in DMSO at 300 °K were studied. [CuL1] complex shows an irreversible peak for the copper(II)/copper(I) couple at Epc1 = 0.16 V and Epa = 0.53V referenced to Ag/AgCl. The cyclic voltammogram of the [CuL2] complex in MeCN at 300°K shows a quasi-reversible peak for the couples copper(II)/copper(III) ...

Synthesis, spectroscopic characterization, redox, and biological screening studies of some schiff base transition metal(ii) complexes derived from salicylidene-4-aminoantipyrine and 2-aminophenol/ 2-aminothiophenol

Cobalt(II) complexes of the Schiff bases 1,2-(diimino-4′-antipyrinyl)ethane (GA) and 4-N-(4′-antipyrylmethylidene)aminoantipyrine (AA) have been prepared and characterised by elemental analysis, electrical conductance in non-aqueous solvents, i.r. and electronic spectra, as well as by magnetic susceptibility measurements. The complexes have the general formulae [Co(GA)X]X (X = ClO−4 or NO3−), [Co(GA)X2] (X = Cl−, Br− or I−), [Co(AA)2]X2 (X = ClO4−, NO3−, Br− or I−) and [Co(AA)Cl2]. GA acts as a neutral tetradentate ligand, coordinating through both carbonyl oxygens and both azomethine nitrogens. In the perchlorate and nitrate complexes of GA one anion is coordinated in a bidentate fashion, whereas in the halide complexes both anions are coordinated to the metal, generating an octahedral geometry around the Co ion. AA acts as a neutral bidentate ligand, coordinating through the carbonyl oxygen derived from the aldehydic moiety and the azomethine nitrogen. Both anions remain ionic in the perchlorate, nitrate, bromide and iodide complexes of AA, whereas both anions are coordinated to the metal ion in the chloride complex, resulting tetrahedral geometry around the Co ion.

Cobalt(II) complexes of 1,2-(diimino-4′-antipyrinyl)ethane and 4-N-(4′-antipyrylmethylidene)aminoantipyrine

4-Aminoantipyrine schiff-base complexes of lanthanide and uranyl ions

Ten new complexes of rare earth iodides with 4-(2′, 4′-dihydroxyphenylazo)antipyrine (H-RAP) of the general formula [Ln(H-RAP)2I2]I (where Ln = Y, La, Pr, Nd, Sm, Eu, Gd, Dy, Ho & Er) have been synthesised and characterized by elemental analysis, electrical conductance in non-aqueous solvents, infrared and electronic spectra, magnetic susceptibilities and thermogravimetric studies. In these complexes H-RAP acts as a neutral bidentate ligand coordinating through carbonyl oxygen and one of the azo nitrogens. Two of the iodines are coordinated and the third one remains as ionic. The magnetic moments of the complexes agree well with the van Vleck values. Thermogravimetric studies in nitrogen indicate that these complexes are stable upto 440 K and undergo complete decomposition in the range 440–1110 K resulting in the formation of the corresponding metal iodides.

P.K. Radhakrishnan

Papers

Complexes of lanthanide nitrates with 4n-(2′-hydroxy benzylidene)-aminoantipyrine