This review focuses on key aspects of the thermal decomposition of multinary or mixed hydride materials, with a particular emphasis on the rational control and chemical tuning of the strategically important thermal decomposition temperature of such hydrides, Tdec. An attempt is also made to predict the thermal stability of as-yet unknown, elusive or even unknown hydrides. The future of a particularly promising class of materials for hydrogen storage, namely the catalytically enhanced complex metal hydrides, is discussed. The predictions are supported by thermodynamics considerations, calculations derived from molecular orbital (MO) theory and backed up by simple chemical insights and intuition.

Thermal decomposition of the non-interstitial hydrides for the storage and production of hydrogen.

The coordination chemistry of pyrazole-derived ligands

Structure and Reactivity of Earlyminus signLate Heterobimetallic Complexes.

A physiological feature of many tumor tissues and cells is the tendency to accumulate high concentrations of copper. While the precise role of copper in tumors is cryptic, copper, but not other trace metals, is required for angiogenesis. We have recently reported that organic copper-containing compounds, including 8-hydroxyquinoline-copper(II) and 5,7-dichloro-8-hydroxyquinoline-copper(II), comprise a novel class of proteasome inhibitors and tumor cell apoptosis inducers. In the current study, we investigate whether clioquinol (CQ), an analog of 8-hydroxyquinoline and an Alzheimer's disease drug, and pyrrolidine dithiocarbamate (PDTC), a known copper-binding compound and antioxidant, can interact with copper to form cancer-specific proteasome inhibitors and apoptosis inducers in human breast cancer cells. Tetrathiomolybdate (TM), a strong copper chelator currently being tested in clinical trials, is used as a comparison. Breast cell lines, normal, immortalized MCF-10A, premalignant MCF10AT1K.cl2, and malignant MCF10DCIS.com and MDA-MB-231, were treated with CQ or PDTC with or without prior interaction with copper, followed by measurement of proteasome inhibition and cell death. Inhibition of the proteasome was determined by levels of the proteasomal chymotrypsin-like activity and ubiquitinated proteins in protein extracts of the treated cells. Apoptotic cell death was measured by morphological changes, Hoechst staining, and poly(ADP-ribose) polymerase cleavage. When in complex with copper, both CQ and PDTC, but not TM, can inhibit the proteasome chymotrypsin-like activity, block proliferation, and induce apoptotic cell death preferentially in breast cancer cells, less in premalignant breast cells, but are non-toxic to normal/non-transformed breast cells at the concentrations tested. In contrast, CQ, PDTC, TM or copper alone had no effects on any of the cells. Breast premalignant or cancer cells that contain copper at concentrations similar to those found in patients, when treated with just CQ or PDTC alone, but not TM, undergo proteasome inhibition and apoptosis. The feature of breast cancer cells and tissues to accumulate copper can be used as a targeting method for anticancer therapy through treatment with novel compounds such as CQ and PDTC that become active proteasome inhibitors and breast cancer cell killers in the presence of copper.

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Clioquinol and pyrrolidine dithiocarbamate complex with copper to form proteasome inhibitors and apoptosis inducers in human breast cancer cells

Organic copper complexes as a new class of proteasome inhibitors and apoptosis inducers in human cancer cells.

Characterization and toxicity of lanthanide complexes with nitrogen- and sulphur-containing Schiff bases

Transition metal complexes of hydrotris(imidazolyl)borate anion

A novel ligand, potassium tetrakis(1-indazolyl)borate has been synthesized from potassium borohydride and indazole at 215°C in a closed assembly. Complexes of this newly synthesized chelate have been prepared with Cu(II), Ni(II), Co(II), Mn(II) and Fe(III) halides. These have been characterized by elemental analysis, IR, reflectance spectra, room temperature magnetic susceptibility- and conductance measurements. Except for the Cu(II) complex, these complexes appear to have an octahedral structure. The molar conductance value of 10−3M solutions of all complexes, except the Ni(II) complex, support nonionic species. B and 10 Dq values have been calculated where appropriate.

Tetrakis(1-indazolyl)borate Complexes with Transition Metals

Potassium dihydro-bis-(1-indazolyl)borate, synthesized from potassium borohydride and indazole, has been used as a reagent to yield complexes with copper(II), nickel(II), cobalt(II), manganese(II) and iron(III) ions. From i.r. spectral studies the ligand is uninegative and bidentate and coordination occurs through the nitrogen atom at position 2 of the indazole ring system in all cases. With the sole exception of the copper(II) complex, the nitrogen atom at position 1 is also involved in forming a bridge with an adjacent metal ion. On the basis of electronic spectral studies and magnetic susceptibility measurements a distorted square planar structure involving chlorine bridges has been proposed for the copper complex. An octahedral geometry with ligand bridges for all complexes is tentatively proposed and it appears that all are polymers.

The synthesis and ligand properties of the dihydro-bis-(1-indazolyl)borate anion

Chlorosulphates of the divalent transition metals Mn(II), Co(II), Ni(II) and CU(II) have been prepared and characterized. The electrical conductivities and i.r. spectral data indicate a considerable extent of cation-anion interaction and the anion is bonded in a tridentate manner such that it has a reduced Cs symmetry in the molecule. The magnetic susceptibility measurements and the ligand field spectroscopic studies are consistent with the octahedral geometry for these salts and indicate the presence of some covalent bonding between the chlorosulphate ion and the metal ion. However, a tetragonal distortion in the geometry has been indicated for the Ni(II) salt. The coordination compounds of the type ML4(SO3Cl)2[L=acetonitrile, pyridine, pyridine N-oxide] and ML2(SO3Cl)2 [L = 2,2′bipyridine, acridine] have also been prepared and characterized. The i.r. and ligand field spectroscopic studies and magnetic susceptibility measurements indicate the presence of a strong interaction between the anion an...

Coordinating Properties of Chlorosulphate Ion; Synthesis and Characterization of Mn (II), Co (II), Ni(II) and Cu(II) Bis-(Chlorosulphates) and Their Complexes with Nitrogen-Containing Bases

S. A. A. Zaidi

Papers

Characterization and toxicity of lanthanide complexes with nitrogen- and sulphur-containing Schiff bases

Transition metal complexes of hydrotris(imidazolyl)borate anion

Tetrakis(1-indazolyl)borate Complexes with Transition Metals

The synthesis and ligand properties of the dihydro-bis-(1-indazolyl)borate anion

Coordinating Properties of Chlorosulphate Ion; Synthesis and Characterization of Mn (II), Co (II), Ni(II) and Cu(II) Bis-(Chlorosulphates) and Their Complexes with Nitrogen-Containing Bases