Replacement of the central Mg in chlorophylls by Ni opens an ultrafast (tens of femtoseconds time range) radiationless de-excitation path, while the principal ground-state absorption and coordination properties of the pigment are retained. A method has been developed for substituting the native bacteriochlorophyll a by Ni-bacteriochlorophyll a ([Ni]-BChl) in the light harvesting antenna of the ...

The mixed-ligand complex [Ni(dppp)(P(Ph)(2)N(Bz)(2))](BF(4))(2), 3, (where P(Ph)(2)N(Bz)(2) is 1,5-dibenzyl-3,7-diphenyl-1,5-diaza-3,7-diphosphacyclooctane and dppp is 1,3-bis(diphenylphosphino)propane) has been synthesized. Treatment of this complex with H(2) and triethylamine results in the formation of the Ni(0) complex, Ni(dppp)(P(Ph)(2)N(Bz)(2)), 4, whose structure has been determined by a...

the stability constants of species present in the systems ni(ii)-pyridoxamine(pym)(a) and ni(ii)-pyridoxamine(pym)(a)-imidazole containing ligands(b) [b = imidazole(him),  benzimidazole(bim), histamine(hist) and l-histidine(his)] have been determined ph-metrically using the miniquad computer program. the existence of the species niah, nia and nia2 was proven for the ni(ii)-pym(a) system, wherea...

Incorporation of first row transition metals into stable surface precipitates can play an important role in reducing the bioavailability of these metals in neutral and alkaline soils. Organic coatings may interfere with this sorption mechanism by changing the surface characteristics and by masking the mineral surface from metal sorptives. In this study, kinetic sorption and desorption experimen...

Meglumine diatrizoate ("Renografin-76", a radiographic contrast medium) contains sufficient nickel to cause hypernickelemia in patients after coronary arteriography. Nickel analyses by electrothermal atomic absorption spectrophotometry showed that nine lots of "Renografin-76" (760 g of meglumine diatrizoate per L) contained 144 +/- 44 micrograms Ni per L. Serum Ni concentrations became elevated...

Rate and activation parameters for the complex-formation reaction of Ni(2+) with 4-(2-pyridylazo)-N,N-dimethyl aniline (PADA) were studied as a function of pH in different buffers in both aqueous and sodium dodecyl sulfate (SDS) micelle solutions. In aqueous Tris buffer solution, the forward and backward rate constants increased with increasing pH, while the complex-formation constant decreased...

The sorption speciation of Ni(II) on Ca-montmorillonite was evaluated using a combination of batch experiments, extended X-ray absorption fine structure (EXAFS) spectroscopy and modeling. The pH and temperature at the aqueous-montmorillonite interface affects both the extent of Ni(II) sorption as well as the local atomic structure of the adsorbed Ni(II) ions. At 0.001 mol L(-1) Ca(NO(3))(2) and...

The reaction of [Ni(L)]Cl(2)·2H(2)O (L = 3,14-dimethyl-2,6,13,17-tetraazatricyclo [14,4,0(1.18),0(7.12)]docosane) with trans-1,2-cyclopentanedicarboxylic acid (H(2)-cpdc) yields a 1D hydrogen-bonded infinite chain with formula [Ni(L)(H-cpdc(-))(2)] (1). This complex has been characterized by X-ray crystallography, spectroscopy and cyclic voltammetry. The crystal structure of 1 exhibits a distor...

The title complex, [Ni(C(10)H(10)N(6))(2)][Ni(CN)(4)]·2H(2)O, contains an octa-hedral nickel(II) cation and a square-planar nickel(II) anion. Both the cation and the anion reside on a crystallographic center of inversion. The Ni(II) center in the cation is coordinated by six pyrazol-1-yl rings of two chelating tripyrazol-1-ylmethane [HC(pz)(3)] ligands, with Ni-N distances that range between 2....