Hydrazone Schiff base-manganese(II) complexes: Synthesis, crystal structure and catalytic reactivity

Dye-sensitized solar cells (DSC) were prepared from nanoporous TiO2 electrodes with two different cobalt complex redox couples, propylene-1,2-bis(o-iminobenzylideneaminato)cobalt(II) {CoII(abpn)} and tris(4,4‘-di-tert-buthyl-2,2‘-bipyridine)cobalt(II) diperchlorate {CoII(dtb-bpy)3(ClO4)2}. The performances of the DSCs were examined with varying the concentrations of the redox couples and Li cations in methoxyacetonitrile. Under 1 sun conditions, short-circuit currents (Jsc) increased with the increase of the redox couple concentration, and the maximum Jsc was found at the Li+ concentration of 100 mM. To rationalize the observed trends of Jsc, electron diffusion coefficients and lifetimes in the DSCs were measured. Electron diffusion coefficients in the DSCs using cobalt complexes were comparable to the previously reported values of nanoporous TiO2. Electron lifetime was independent of the concentration of the redox couples when the concentration ratio of CoII(L) and CoIII(L) was fixed. With the increase o...

Roles of Electrolytes on Charge Recombination in Dye-Sensitized TiO2 Solar Cells (2): The Case of Solar Cells Using Cobalt Complex Redox Couples

Coordination geometry of tetradentate Schiff’s base nickel complexes: the effects of donors, backbone length and hydrogenation

A series of easily accessible and stable Schiff-base nickel complexes (complex 1-4) in conjunction with methylaluminoxane (MAO) were employed for the synthesis of relatively high molecular weight β-pinene polymers at high temperature with high productivity. The ligand structure of the complex had a substantial effect on the polymerization in terms of the productivity and the molecular weight. With complex 4 in the presence of MAO, high molecular weight polymers of β-pinene (M n ∼ 10,900) were obtained at 40 °C with an extremely high productivity up to 1.25 x 10 7 g poly β-pinene/mol of Ni. 1 H NMR analyses showed that the obtained β-pinene polymer was structurally identical to that formed by conventional cationic Lewis acid initiators. The polymerization was presumably initiated by the nickel cation formed by the reaction of the Schiff-base nickel complex and MAO, while the propagation proceeded in a manner typical for a conventional carbocationic polymerization process. Direct evidence for the carbocationic polymerization was offered by the fact that quenching of the polymerization with methanol at a low monomer conversion resulted in incorporation of a methoxyl end group into the polymer chain.

Polymerization of β-pinene with Schiff-base nickel complexes catalyst: Synthesis of relatively high molecular weight poly(β-pinene) at high temperature with high productivity

The synthesis and characterization of the two homoleptic mononuclear nickel complexes (2,6-Dipp2C6H3NH)2Ni (1) and [2-C(H)NDippC6H4NH]2Ni (2) (Dipp = 2,6-Pri2C6H3) are described. 1 is formally two-coordinate and adopts a strictly linear geometry, while 2 features a slightly distorted square-planar geometry. Electrochemistry of 1 and 2 shows that they can be reduced to the corresponding nickel(I) species and oxidized to the corresponding nickel(III) species reversibly or quasi-reversibly. A solid-state magnetic measurement (μeff = 2.79 μB) for paramagnetic 1 indicates the presence of two unpaired electrons on the nickel center.

Synthesis and characterization of linear and square-planar nickel complexes with primary amido ligands.

An investigation is reported of the structure and some reactions of the cobalt(II), nickel(II), and copper(II) compounds of several tricyclic quadridentate di-anionic Schiff's base ligands derived from o-aminobenzaldehyde and various diamines. The ligands are 1,2-bis-(o-iminobenzylideneamino)ethane (aben), 1,2-bis-(o-iminobenzyl-ideneamino)propane (abpn), 1,3-bis-(o-iminobenzylideneamino)propane (abtn), and 1,2-bis-(o-iminobenzylideneamino)phenylene (abphen). The physicochemical data presented are supplementary to that of two recent papers in proving a four co-planar co-ordination polyhedron in the metal(II) compounds. In addition, a polarographic study of the redox behaviour of these compounds indicates that all should have chemically accessible higher oxidation states. Attempts to prepare the nickel and copper oxidation products of the type [M(L)X](X= Br, I) gave only amorphous solids which have not been characterised. But the crystalline compounds [Co(L)X](X= Cl, Br, I) which were readily isolated, are unique examples of paramagnetic cobalt(III) compounds with nitrogen-donor ligands. A square-pyramidal five-co-ordinate structure is postulated. These compounds react in donor solvents such as pyridine to form six-co-ordinate diamagnetic species of the type [Co(L)(solvent)X]. The crystalline diamagnetic compound [Co(aben)(py)Cl] has been isolated, and evidence is given for an equilibrium in the solutions in donor solvents between the diamagnetic and paramagnetic species.

The structure, redox properties, and reactions of some planar [MIIN4] chelate compounds of cobalt, nickel, and copper, and their oxidised products, including paramagnetic cobalt(III) species

E. D. McKenzie

Papers

The structure, redox properties, and reactions of some planar [MIIN4] chelate compounds of cobalt, nickel, and copper, and their oxidised products, including paramagnetic cobalt(III) species