Ligand concentration effect

Benzene, benzene-d , and fluorobenzene were found (770, 777) to react with chromium, cobalt, iron, and nickel atoms on codeposition in the neat ligand at 77 K, or in argon matrices at 10-12 K. IR studies of the products indicated that the initial reaction of these transition-metal atoms with an aromatic system is 7r-complex formation. Studies of ligand concentration-effects showed that the chromium-atom reaction is approximately second-order with respect to benzene, yielding the previously known (782) complex (CeH6)2Cr, whereas, with the other metals, the reaction is first-order, yielding MfCsHs), M = Co, Fe, or Ni. The absence of CrfCeH ) is probably a reflection of (a) the fact that the... 

In view of the magnitude of crystal-field effects it is not surprising that the spectra of actinide ions are sensitive to the latter s environment and, in contrast to the lanthanides, may change drastically from one compound to another. Unfortunately, because of the complexity of the spectra and the low symmetry of many of the complexes, spectra are not easily used as a means of deducing stereochemistry except when used as fingerprints for comparison with spectra of previously characterized compounds. However, the dependence on ligand concentration of the positions and intensities, especially of the charge-transfer bands, can profitably be used to estimate stability constants. 

The effect of Rh concentration on the selectivity was negligible. The ligand concentration, on the other hand, is expected to have a considerable effect on the selectivity thus experiments were carried out with different ligand concentrations. A higher ligand concentration retards the overall rate, but increases the selectivity to pentanal. At the lowest L/Rh ratio (10), the ratio pentanal-to-2-methylbutanal was about 3.4, while it became about 5 for the highest L/Rh ratio (10). 

In an extension of the FIAM model, the biotic ligand model of the acute toxicity of metals assumes that a given toxic effect occurs when the concentration of metal bound to biotic ligands exceeds a certain threshold concentration [203-205]. This model has been successfully applied to rationalise toxicity data from fish and Daphnia. Although the identity and abundance of biotic ligands is not known, modelling has revealed that the critical biotic ligand concentrations are much lower in Crustacea than in fish [203,204],... 

Munro AM, Plante IJL, Ng MS, Ginger DS (2007) Quantitative study of the effects of surface ligand concentration on CdSe nanocrystal photoluminescence. J Phys Chem C 111 6220-6227... 

Aryl phosphites were among the first ligands that were extensively studied. The results obtained with triphenylphosphine and triphenyl phosphite are strikingly similar at low ligand concentrations. At higher ligand metal ratios phosphites may retard the reaction. The electronic and steric properties of the phosphite have a large effect on the rate and selectivity of the reaction. 

Effect of ligand concentration on the apparent rate constant (kapp) for (a) a pseudo first order reaction (O Eq.22) or a two-step reaction (O Eq.23). The data in (a) were generated using ki and k i values of 2 x 10 and... 

Concentration-effect curves of agonists at Torpedo nAChR expressed in oocytes. Potency of ligands suber-yldicholine ( ) > acetylcholine ( ) > PTMA (O) (unpublished observations)... 

The second-order reaction with adsorption of the ligand (2.210) signifies the most complex cathodic stripping mechanism, which combines the voltammetric features of the reactions (2.205) and (2.208) [137]. For the electrochemically reversible case, the effect of the ligand concentration and its adsorption strength is identical as for reaction (2.205) and (2.208), respectively. A representative theoretical voltammo-gram of a quasireversible electrode reaction is shown in Fig. 2.86d. The dimensionless response is controlled by the electrode kinetic parameter m, the adsorption... 

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