Weak interactions between metals

Applying this to our electrochemical system could qualitatively explain some of the observed effects. Assuming that there is only a weak interaction between metal and the perchloric acid hydrate, protons being part of the clathrate structure may not be in a favorable position for a charge transfer reaction at the interface. This could result in small pre-exponential factors. The electrode potential, however, may... 

Weak Interactions between Metals through a Bridging Ligand... 

SN)x are free to move under the influence of an applied potential difference and thus conduction occurs along the polymer chain. The S-N distances in the chain are essentially equal, consistent with a delocalized structure. The increase in conductivity with decreasing temperature is characteristic of a metallic conductor. The predicted Peierls distortion is apparently inhibited by weak interactions between the polymer chains (S—S = 3.47-3.70 A S—N = 3.26-3.38 A.). ... 

Compounds containing Mg bonded to an inner transition metal or other group-IIA metals bonded to transition metals are not known. Compounds such as I, in which there are only weak interactions between Mg and M, are excluded from this discussion. 

The relationship between film thickness of hexadecane with the addition of cholesteryl LCs and rolling speed under different pressures is shown in Fig. 25 [50], where the straight line is the theoretic film thickness calculated from the Hamrock-Dowson formula based on the bulk viscosity under the pressure of 0.174 GPa. It can be seen that for all lubricants, when speed is high, it is in the EHL regime and a speed index 4> about 0.67 is produced. When the rolling speed decreases and the film thickness falls to about 30 nm, the static adsorption film and ordered fluid film cannot be negligible, and the gradient reduces to less than 0.67 and the transition from EHL to TFL occurs. For pure hexadecane, due to the weak interaction between hexadecane molecules and metal surfaces, the static and ordered films are very thin. EHL... 

The longer metal-oxygen distances of about 2.6 A observed by EXAFS spectroscopy for these and related supported metal clusters suggest weak interactions between the metal and surface oxygen atoms these EXAFS contributions are not determined with as much confidence as those characterized by the shorter distances, and the interactions are not well understood. 

Despite the fact that the electrodeposition of copper and silver at the water-DCE and the water-dichloromethane interfaces has been generally regarded as the first experimental evidence for heterogeneous ET at externally biased ITIES [171], a very limited amount of work has dealt with this type of process. This reaction has also theoretical interest because the molecular liquid-liquid interface can be seen as an ideal substrate for electrochemical nucleation studies due to the weak interactions between the interface and the newly formed phase and the lack of preferential nucleation sites always present at metallic electrodes. 

The X-ray structures of two ortho-metalated compounds, (166), have been discussed.310 Weak interactions between the hydride ligand and C—H protons of the PPh3 groups are recorded. 

Detailed studies about metal deposition from the gas phase onto SAMs have been published [108-110], The central question for the system substrate/SAM/deposit there (as well as in electrochemistry) is the exact location of the deposited metal On top of the SAM or underneath Three clearly different situations are easily foreseen (Fig. 31). (1) Metal on top of the SAM. Depending on a strong or weak chemical interaction between metal and SAM (e.g., functional end group of the SAM), the deposit will spread out on top of the SAM or it will cluster on the SAM. (2) Metal penetrating the SAM (e.g., at defects in the SAM) and connecting to the metal substrate underneath the SAM. This configuration is often pictured as a mushroom, with a thin connective neck and a large, bulky head. (3) Deposited metal is inserted be-... 

In most palladium-catalyzed oxidations of unsaturated hydrocarbons the reaction begins with a coordination of the double bond to palladium(II). In such palladium(II) olefin complexes (1), which are square planar d8 complexes, the double bond is activated towards further reactions, in particular towards nucleophilic attack. A fairly strong interaction between a vacant orbital on palladium and the filled --orbital on the alkene, together with only a weak interaction between a filled metal d-orbital and the olefin ji -orbital (back donation), leads to an electrophilic activation of the alkene9. 

One can distinguish between physical and chemical methods of immobilization (Fig. 42.2). The former makes use of weak interactions between the metal... 

Herdt GC, Jung DR, Czandema AW (1995) Weak interactions between deposited metal overlayers and organic functional groups of self-assembled monolayers. Prog Surf Sci 50 103-129... 

Fig. 9.4.29 Comparison of stability of metallic nanoparticles in bulk liquid with a droplet on a metal surface, (a) Wetting of a droplet on a metal surface, (b) Coagulation and dispersion of metallic particles in liquid. Figures on the left-hand side stand for weak interaction in case A causing coagulation in case B. Those on the right-hand side are a strong interaction between metal and liquid, suggesting good dispersion and good contact.

Since the metal center in gold complexes usually displays acid character, Au- -NM contacts will be more easily formed as the basicity of the non-metal increases. Thus, there are many gold- -halogen weak interactions between cationic gold complexes and halides or anions of which the halogen forms part, but most are individual contacts between ions that do not generate supramolecular structures. For example, about 50% of Au- -Cl contacts are isolated cation- -anion interactions. 

ECL investigations of dinuclear or polynuclear Ru(II) complexes have been recently performed with hope for developing more efficient electrochemiluminescent materials. Centrally or peripherally functionalized dendrimers with active RuL32 + chelate units can produce higher (up to four to five times) ECL intensities as compared to their monomeric RuL32 + precursors alone. It was also found that the ECL intensities of metallodendrimers become larger as the multiplicity of the involved Ru(II) units increases. Similar observations have been reported for binuclear Ru(II) complexes with weak interaction between both metallic centers.84-88 These results indicate that further studies in such direction may result in design of still more efficient ECL systems based on Ru(II) luminophores. 

Metal Ion Catalysis Metals, whether tightly bound to the enzyme or taken up from solution along with the substrate, can participate in catalysis in several ways. Ionic interactions between an enzyme-bound metal and a substrate can help orient the substrate for reaction or stabilize charged reaction transition states. This use of weak bonding interactions between metal and substrate is similar to some of the uses of enzyme-substrate binding energy described earlier. Metals can also mediate oxidation-reduction reactions by reversible changes in the metal ion s oxidation state. Nearly a third of all known enzymes require one or more metal ions for catalytic activity. 

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