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Schiff bases are considered as privileged ligand in coordination chemistry as they easily form stable complexes with most transition metal complexes. In this paper, a novel Schiff-base ligand derived from Curcumin and Semicarbazide (HMHC) and its transition metal [Mn(II), Co(II), Ni(II), Cu(II) and Zn(II)] complexes were synthesized. FT-IR, UV–Vis, NMR, Mass, TG-DTA and ESR spectral techniques were used to confirm the structures of the metal chelates and ligand. The Schiff base behaves as a tridentate ligand with O and N donors and coordinates to metal ion via phenolic oxygens and azomethine nitrogen. The compositions of the ligand and its metal complexes have been established by elemental analysis. Spectral investigations suggested octahedral geometrical arrangement for all the metal(II) complexes, having 2:1 (L:M) stoichiometric ratio of the type [M(HMHC)2]H2O. The Schiff base ligand and its metal complexes have been screened for antimicrobial evaluation towards some clinically important microorganisms. Result found that the metal complexes were more active than the ligand. Also anti-inflammatory activity of Schiff base complexes were studied by protein denaturation method and result reveals that Zn(II) complex shows more activity.

A biodegradable polymer was synthesized by the modification reaction of polymeric starch with thiourea which is further modified by transition metals, Mn(II), Co(II), Ni(II), Cu(II) and Zn(II). All the polymeric compounds were characterized by (FT-IR) spectroscopy, 1H NMR spectroscopy, 13C NMR spectroscopy, UV–visible spectra, magnetic moment measurements, thermogravimetric analysis (TGA) and antibacterial activities. Polymer complexes of Mn(II), Co(II) and Ni(II) show octahedral geometry, while polymer complexes of Cu(II) and Zn(II) show square planar and tetrahedral geometry, respectively. The TGA revealed that all the polymer metal complexes are more thermally stable than their parental ligand. In addition, biodegradable studies of all the polymeric compounds were also carried out through ASTM-D-5338-93 standards of biodegradable polymers by CO2 evolution method which says that coordination decreases biodegradability. The antibacterial activity was screened with the agar well diffusion method against some selected microorganisms. Among all the complexes, the antibacterial activity of the Cu(II) polymer–metal complex showed the highest zone of inhibition because of its higher stability constant.

Abstract: The stereochemistry and coordination behavior of Co(II) and Cu(II) complexes of a novel 18-membered quadridentate macrocyclic ligand (3,4,12,13-tetraphenyl-1,2,5,6,10,11,14,15-octaazacyclooctadecane-7,9,16,18-tetraone-2,4,11,13-tetraene) have been investigated after their template synthesis. The synthesized macrocycles have been characterized by means of various physicochemical techniques viz. elemental analyses, magnetic, conductivity measurements,and spectral (IR, electronic, mass and EPR) techniques. The structure of complexes has been determined with the help of spectroscopic as well as conductivity values and found to be six coordinated octahedral and tetragonal for Co(II) and Cu(II), respectively. The ligand was coordinated to the metal ion via the malonylhydrazide moiety’s imine nitrogen in a tetradentate fashion. Molar conductance measurements revealed that reported macrocyclic complexes were non-ionic in nature. All the complexes have been screened for their in vitro antifungal activity against a number of fungi isolated from plants. The compounds exhibit significant antifungal activity. [Copyright &y& Elsevier]

Abstract: New cobalt(II) and nickel(II) complexes of 4N-substituted thiosemicarbazones derivatives of 2-methylcyclohexanone of general composition ML2X2 (where M=Co(II) and Ni(II), X=Cl−, SCN− and ½) have been prepared and characterized by elemental analysis, molar conductance, magnetic susceptibility measurements and spectral (IR, electronic, mass and EPR) techniques. Thiosemicarbazones exist in thione form and coordinate to metal ion through sulphur atom of Cnd azomethine nitrogen. Spectral studies suggest an octahedral geometry for all the complexes. The complexes and ligands have also been tested in vitro for their antifungal activity. The experimental results suggest that metal chelates are more potent than their parent ligands. [ABSTRACT FROM AUTHOR]

Schiff bases are considered as privileged ligand in coordination chemistry as they easily form stable complexes with most transition metal complexes. In this paper, a novel Schiff-base ligand derived from Curcumin and Semicarbazide (HMHC) and its transition metal [Mn(II), Co(II), Ni(II), Cu(II) and Zn(II)] complexes were synthesized. FT-IR, UV–Vis, NMR, Mass, TG-DTA and ESR spectral techniques were used to confirm the structures of the metal chelates and ligand. The Schiff base behaves as a tridentate ligand with O and N donors and coordinates to metal ion via phenolic oxygens and azomethine nitrogen. The compositions of the ligand and its metal complexes have been established by elemental analysis. Spectral investigations suggested octahedral geometrical arrangement for all the metal(II) complexes, having 2:1 (L:M) stoichiometric ratio of the type [M(HMHC) 2 ]H 2 O. The Schiff base ligand and its metal complexes have been screened for antimicrobial evaluation towards some clinically important microorganisms. Result found that the metal complexes were more active than the ligand. Also anti-inflammatory activity of Schiff base complexes were studied by protein denaturation method and result reveals that Zn(II) complex shows more activity. [ABSTRACT FROM AUTHOR]

A biodegradable polymer was synthesized by the modification reaction of polymeric starch with thiourea which is further modified by transition metals, Mn(II), Co(II), Ni(II), Cu(II) and Zn(II). All the polymeric compounds were characterized by (FT-IR) spectroscopy, 1 H NMR spectroscopy, 13 C NMR spectroscopy, UV–visible spectra, magnetic moment measurements, thermogravimetric analysis (TGA) and antibacterial activities. Polymer complexes of Mn(II), Co(II) and Ni(II) show octahedral geometry, while polymer complexes of Cu(II) and Zn(II) show square planar and tetrahedral geometry, respectively. The TGA revealed that all the polymer metal complexes are more thermally stable than their parental ligand. In addition, biodegradable studies of all the polymeric compounds were also carried out through ASTM-D-5338-93 standards of biodegradable polymers by CO 2 evolution method which says that coordination decreases biodegradability. The antibacterial activity was screened with the agar well diffusion method against some selected microorganisms. Among all the complexes, the antibacterial activity of the Cu(II) polymer–metal complex showed the highest zone of inhibition because of its higher stability constant. [ABSTRACT FROM AUTHOR]