Ligand balance

In this particular example, we can also interpret (4.2-2) in a different way, namely as a proton balance, an expression in which we specify which solution species have gained protons by comparison with the starting materials (here H20 and HA) and which have lost protons. The proton balance focuses on H+, the species of interest in pH calculations. Likewise, in complexation equilibria, we will encounter an analogous ligand balance, and in electrochemical equilibria an electron balance. 

Again, we have not included activity corrections, because (both didactically and computationally) these are best added afterwards whenever such corrections are required. The principles involved are the same as those explained in section 4.10 activity corrections apply to the equilibrium constants (such as Kfl, Ksl, and k) but not to the mass and charge balance relations and their derivatives, such as a ligand balance or an electron balance. Furthermore, electrometric measurements must be corrected for activity effects, but spectroscopic measurements should not be. At any rate, as the example of HgS in section 5.4 illustrates, the proper chemistry of including all important species is always far more important than the proper physics of making activity corrections. 

A spreadsheet is constructed with values of log [CP] from 0 to -5.0 in steps of 0.1 or 0.2 in column A and, in successive columns the quantities [Cl], ttpb, S, the remaining values, and the log functions of all of these. From a ligand balance equation ... 

Two principal features characterize the systematic approach to equilibrium calculations used in this book a) Expressing concentrations of every species by the product of a (a fraction of that species of all others in the same system. These fractions are a function of only the critical variable (e.g., pH), the relevant equilibrium constants, and C, the total concentration of the component, and b) Describing the equilibrium condition by a single balance equation, e.g., the proton balance equation (PBE), the ligand balance equation, etc. This results ultimately in a description of the equilibrium condition of the solution by one equation with a single concentration variable, i.e., in an implicit solution. 

For one thing, it is hard to generalize about how the various enthalpic and entropic effects of dehydration of the cavity and the ligand balance out. Both... 

The bipyridyl ligand, with 80 %, gives the best catalyst, probably because it affords the best balance between the a-donor and rt-acceptor characters which favours respectively the oxidative addition of the aryl bromide and the reductive elimination of the aryl ether at the nickel center. 

The number of valence electrons in niobium oxychloride clusters decreases as the number of oxide hgands increases (Table 6.4). The compound Cs2LuNbi Cli70 has the VEC of 16 as found in most chloride clusters, suggesting that the presence of one oxide ligand per cluster does not tip the balance between the Nb-Nb bonding and Nb-L anti-bonding contributions to the a2u state. The VEC of most clusters... 

The chloride ions that appear outside the brackets represent chloride anions that balance the positive charge on the coordination compound. When a coordination compound dissolves in water, the ligands (inside the brackets) remain bound to the metal cation, but the nonligands (outside the brackets) exist as individual ions. These chloride ions precipitate in the presence of silver ions. The chloride ions inside the brackets, which are ligands bonded to the cobalt center, do not precipitate as AgCl. 

Liu Y, Jones M, Hingtgen CM, Bu G, Laribee N, Tanzi RE, Moir RD, Nath A, He JJ (2000) Uptake of HIV-1 tat protein mediated by low-density lipoprotein receptor-related protein disrupts the neuronal metabolic balance of the receptor ligands. Nat Med 6 1380-1387... 

Fig. 16.4 Interaction between quercetin (Quer) and iron and the balance between pro-oxidative and antioxidative effects. Quercetin may reduce Fe(H20) to yield Fe(H20) active in the Fenton region forming hydroxyl radicals ( OFI) or alkoxyl radicals ( OR), in effect being pro-oxidative. In contrast, quercetin may form a complex with iron(II), inactive in reducing FI2O2 to OFI, but rather oxidised in the quercetin ligand, in effect being antioxidative. Quer (-H) is the phenoxyl radical.

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