On the Study of Racah Parameter B for Nickel (II) and Cobalt (II) Compounds

 The ligand field strength (Dq) and interelectronic repulsion (B) have been calculated for nickel (II) and cobalt (II) compounds by Underhill and Billing [1] based on v2 and v3 values. They solved the quadratic equation 340(Dq2-18(v2+v3) Dq+ v2 v3=0 in Dq for octahedral. Then, the B value was determined using the equation v2+ v3−30Dq−15B=0. But, the first equation has real and imaginary solutions and it’s difficult to determine the imaginary one. In addition, in many cases there is no solution of this equation as well as in the case of CoO (d7 oct.). For octahedral, the above two equations can be considered as a system of two equations with two unknowns which can be solved if we have v2 and v3 values and vice versa. Similarly, for tetrahedral, the former two equations also can be solved for Dq and B. Using Newton–Raphson iterations, Dq and B values are exactly determined for octahedral and tetrahedral systems. The obtained values of Dq and B were compared with those previously reported

Coordination versatility of N2O4 polydentate hydrazonic ligand in Zn(II), Cu(II), Ni(II), Co(II), Mn(II) and Pd(II) complexes and antimicrobial evaluation

New polydentate hydrazone ligand, was synthesized by the condensation of 1,5-dimethyl-3-oxo-2-phenylpyrazole-4-carbaldehyde with adipodihydrazide. The structure of the synthesized ligand, Nâ²1,Nâ²6-bis((1,5-dimethyl-3-oxo-2-phenyl-2,3-dihydro-1H-pyrazol-4-yl) methylene) adipohydrazide was elucidated by various analytical and spectroscopic techniques. The reactions of the ligand with zinc(II), copper(II), nickel(II), cobalt(II), manganese(II) and palladium(II) salts afforded homobinuclear metal complexes. Characterization and structure elucidation of the prepared complexes were achieved using different analytical and spectroscopic techniques. The analyses data indicated that this ligand behaved as N2O4 dibasic hexadentate ligand bonded covalency to the metal ions through the enolic carbonyl oxygen of hydrazide moiety and coordinated via carbonyl oxygen of antipyrine moiety and azomethine nitrogen atoms forming distorted octahedral geometry around the metal ions. The ESR spectra of copper(II) complexes (3) and (4) showed an axial symmetry with g||>gâ¥>ge, indicating distorted octahedral structure and presence of the unpaired electron in d(x2ây2) orbital. The microbicide studies of the ligand and its metal complexes (2), (3), (4), (5), (8), (11) and (13) showed that, all these complexes exhibit moderate to mild inhibitory effects on B. subtilis, E. coli while complexes (2), (3), (4) and (13) exhibit moderate to mild inhibitory effects on A. niger. Keywords: Hexadentate, Hydrazone, Antipyrine, ESR, Adipohydrazide, Microbicid

Synthesis, physicochemical studies and biological evaluation of unimetallic and heterobimetallic complexes of hexadentate dihydrazone ligands

A new coordination unimetallic and heterobimetallic complexes of hexadentate N2O4 donor dihydrazone ligands were prepared by the condensation of 4-formyl antipyrine with adipic dihydrazide and succinic dihydrazide. The ligands (1) and (11) and their complexes thoroughly characterized using various analytical, physical and spectroscopic techniques, which indicate a distorted octahedral geometry around the metal ions. The ESR spectra of solid copper(II) complexes (2–4) and (12–14) showed axial symmetry with g||>g⊥ > ge, indicating distorted octahedral structure and the presence of the unpaired electron in a d(x2−y2) orbital with significant covalent bond character. The antimicrobial activity results of the metal compounds (2–5), (7), (10), (12–15) and (17) show that, all these complexes exhibit inhibitory moderate to mild effects towards Bacillus subtilis, Escherichia coli and Aspergillus niger