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Abstract: Reaction of tridentate ONS donor ligands H2L1, H2L2 and H2L3 (H2L1 =2-hydroxyacetophenone hexamethyleneimine-3-thiosemicarbazone; H2L2 =2-hydroxyacetophenone morpholine-3-thiosemicarbazone; H2L3 =2-hydroxyacetophenone N(4)-methyl, phenyl thiosemicarbazone) with Mn(OAc)2 ·4H2O afforded manganese(IV) complexes of the type [MnL2] in an ethanol–methanol mixture under air. The crystal structure of Mn(L2)2 ·0.25H2O reveals an octahedral geometry with the ligand coordinated in a meridional fashion. The molecule is packed in the crystal lattice with extended hydrogen bonding networks. EPR spectra of the complexes in frozen solution at 77K show a weak signal at g ≈4 and a strong sextet at g ≈2 consistent with manganese(IV) in an octahedral environment. Cyclic voltammetry in DMSO/ dichloromethane show quasi-reversible peaks corresponding to the Mn(IV)/Mn(III) redox couple. [Copyright &y& Elsevier]

The spectral studies and structure of a ternary complex of copper(II) with 2-hydroxyacetophenone 3-hexamethyliminylthiosemicarbazonate (L2−) and 1,10-phenanthroline (phen) are reported. The thiosemicarbazone binds to the metal as a dianionic ONS-donor (L2−) ligand, and forms a complex of the stoichiometry [CuLphen]. The copper(II) complex was characterized by IR and UV/Vis spectroscopies, as well as by solid state room-temperature magnetic susceptibility. Spin Hamiltonian and bonding parameters of the compound are calculated from the EPR spectra. Computer simulation of EPR spectrum in DMF at 77 K aided the calculation of magnetic and bonding parameters of the compound. The structure of the compound is solved by single crystal X-ray diffraction. The geometry around copper is distorted square pyramidal. [Copyright &y& Elsevier]

An interesting series of eight neutral ternary Co(III) complexes of 2-hydroxyacetophenone N(4)-substituted thiosemicarbazones (H2L), bidentate heterocyclic bases 2,2′-bipyridine (bipy)/1,10-phenanthroline (phen) and azide with a general formula [MLB(N3)] were prepared. The complexes were characterized by means of spectroscopic methods. The coordination geometry around Co(III) in all the complexes is distorted octahedral with one dibasic tridentate ligand L2−, one bidentate heterocyclic base and one terminally coordinated azide group. Crystal structure of the compound CoL4bipyN3 was completely solved. All the electronic transitions were assigned. All complexes were diamagnetic indicating cobalt in a d6 strong field. [Copyright &y& Elsevier]

An interesting series of four complexes of acenaphthoquinone 3-(4-benzylpiperidyl) thiosemicarbazones (HL), with a general formula [Co II L 2 ]( 1 ), [Ni II L 2 ]( 2 ), [Cu II L 2 ]( 3 ), and [Zn II L 2 ]( 4 ), were prepared. The complexes were characterized by means of elemental analysis, IR, UV–Vis spectroscopy and ESI-MS methods. In all the complexes the ligand (HL) coordinate as a monobasic ligand in tridentate fashion. The crystal structure of the compounds 1 and 2 were determined by single crystal X-ray diffraction experiment. The geometry and bonding parameters of the compound 3 were determined from EPR spectra. The g values of 3 , calculated from EPR at 77 K, indicate a rhombic coordination geometry about copper(II). The room temperature magnetic moment of the cobalt(II) complex 1 , indicate that it is in high spin state, while the nickel(II) complex, 2 , is paramagnetic. The redox behavior of the ligand and its complexes were studied by cyclic voltammetry. The density functional theory (DFT) was used for geometry optimization, determination of HOMO and LUMO energies, HOMO–LUMO energy gap and dipole moment of the compounds. Antibacterial activity of the ligand and complexes 1 – 4 , have been screened against two gram negative bacteria Escherichia coli , Pseudomonas aeruginosa and two gram positive bacteria Staphylococcus aureus and Bacillus subtilis. The electron micrograph images display damage to microbial cell wall upon treatment with the compounds. [ABSTRACT FROM AUTHOR]