Complex formation, interfacial metals

The concept sounds attractive, but there is a flaw in the explanation. Assuming an equilibrium situation between the two bulk phases and the interphase, complex formation at the interfacial region requires the same complexes are formed also in the bulk phases. Consequently, in order to produce a considerable amount of the mixed species MA, xBx in the liquid-liquid boundary layer some B must be dissolved in the aqueous, as weU as some A in the organic phase. Since by definition this condition is not met, the relative amount of M present at the interphase region as MAn xBx must be negligible. However, now the metal ion will be distributed between MA in the aqueous phase and MBp in the organic layer (n and p are the... 

Case 2 The rate-determining step of the extraction reaction is the interfacial formation of the complex between the metal ion and the interfacially adsorbed extracting reagent. Here, the rate-determining step of the extraction reaction can be written as... 

The complex formation proceeded almost completely at the interface. The rate constant of k=5.3xl02M 1 s 1 was determined by a stopped-flow spectrometry in the region where the formation rate was independent of pH. The conditional interfacial rate constants represented by k[ = k k2 [HL] / (k2 + k i[H + ]) were larger in the heptane-water interface than the toluene-water interface, regardless of metal ions. The molecular dynamics simulation of the adsorptivities of 5-Br-PADAP in heptane-water and toluene-water interfaces suggested that 5-Br-PADAP could be absorbed at the interfacial region more closely to the aqueous phase, but 5-Br-PADAP in the toluene-water... 

In order to monitor the progress of interfacial reactions occurring during the metallization of cured polyimide, x-ray photoemission spectroscopy (XPS or ESCA) was used to reveal electronic core-levels indicative of the environment at the interface and adjacent regions. Evidence of chemical reaction would include the appearance of new peaks with characteristic binding energies (chemical shifts) representative of new or altered chemical states of the element. We can thus ascertain the formation of metal-oxygen chelate complexes (1). 

In order to investigate the interfacial chemistry and the possible formation of metal-polymer complex, molecular ions containing metal atom and PET fragments are researched. However these peaks may interfere with PET peaks already present and, as shown in Table 1, the isotopic mass resolution of the gwadrupole spectrometer does not allow to resolve the mass interferences for... 

Two significant results have emerged from the CPC separations of metals ions, namely (a) separation efficiencies are significantly reduced by slow metal-complex formation and dissociation kinetics and (b) CPC separations can be entirely interfacially driven analogous to conventional liquid chromatography. 

The stability of the host-guest complex is significantly affected by the nature and composition of the solvent in which the processes occur. This is an important factor when the reaction is carried out in aqueous medium, where hydrophobic interactions mainly contribute to the energy of complex formation due to an increase in its stability. In this regard, the use of water-soluble macrocycles with hydrophobic cavities as components of water-soluble metal complexes in two-phase catalytic systems is of particular interest [38,39]. The catalyst, soluble in the aqueous phase, can be easily separated from the water-insoluble reaction products and reused. It should be emphasized that the activity of conventional catalysts is very low for the reactions involving substrates poorly soluble in water. Due to the formation of water-soluble inclusion host-guest complexes, the macrocyclic receptors not only influence the activity and selectivity of the reaction, but also perform the function of interfacial substrate carrier in aqueous phase. 

DBC complexes with metal salts in the water-benzene system are the products of the interfacial reaction [119]. The measured work of adsorption (15.9 kJ/mol) can be taken as a sum of the free energy of complex formation and work of adsorption of DBC at the water-benzene interface. The dissolution of complexes in bulk phases was neglected. The interfacial constants of complex formation (Table 3) calculated from the work of adsorption are close to the constants determined in the mixed solvent - water-tetrahydrofuran [114]. The only exceptions are the complexes of DBC with Ba " and La salts. Apparently this is due to stronger Coulomb repulsion of ions in DBC-salt complexes at the interface as compared to the bulk phases. (At the interface, the anions... 

FIG. 28. The formation of upd layers often involves complex interactions between the anion, upd metal, and substrate. An example is provided by the (Vs X vVs) R30° STM image of the copper/sulfate upd layer formed on Au(lll) and the SXS of the interfacial structure. (Adapted from Refs. 148, 351, 353.)... 

Case 3 There are two interfacial rate-determining steps, consisting of 1) formation of an interfacial complex between the interfacially adsorbed molecules of the extractant and the metal ion and (2) transfer of the interfacial complex from the interface to the bulk organic phase and simultaneous replacement of the interfacial vacancy with bulk organic molecules of the extractant. For this mechanism, we distinguish two possibilities. The first (case 3.1) describes the reaction with the dissociated anion of the extracting reagent, B"(ad). The second (case 3.2) describes the reation with the undissociated extractant, BH(ad). 

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