Quantifying Ligand Effects

Industrial practice naturally requires the maximum use of the relatively expensive extractant, so that saturation of the extractant phase with reduction of the free ligand concentration to a minimum is the general rule. A model is thus needed to quantify the effect of a reduction in Dx as the concentration of the extracted species in the organic phase increases. 

One simple way of quantifying steric effects in actinide complexes [the cone angle factor (caf) approach] uses the sum of the solid angles subtended by the ligands to the centre of the metal... 

In recent years, many functional assays have been developed to quantify the effect of ligands on CKR function. Concentration-response curves, in which the functional response of a ligand is plotted as a function of its concentration (Fig. 9A), provide information on ligand efficacy and... 

Here we review our work aimed at correlating the reactivity of a series of M(II) N4-ligands, see Figure 12.1, (M = Co, Fe, Mn and N4 = porphyrin (P), phthalocyanine (Pc), teraphenylporphyrin (TPP), tetrabenzoporphyrin (TBP) and tetraazaporphyrin (TAP)) towards the electrocatalytic oxidation of 2-mercaptoethanol. Different effects will be analysed, namely the role of the metal atoms, the role of the N4 functionalisation, solvent and the impact of the adsorption on the electrode on the electrochemical activity. The whole machinery of DFT and the notions of hardness, chemical potential, intramolecular hardness and elec-trophilicity are used to better quantify these effects and discriminate between the examined molecular complexes. 

Extensive data are now available to quantify ligand additivity effects on E values. In a detailed study by Lever, " ligand electrochemical parameters for over 200 ligands are presented and the model proposed has been tested with a wide range of coordination complexes (see Section 2.15.2.4). In the more sophisticated models, the E value is described in terms of the sum of factors involving the ligand electrochemical parameter and the metal. As expected, Ef depends on the... 

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