Electronic interactions decreased

Santos E, Schmickler W. 2008. Electronic interactions decreasing the activation harrier for the hydrogen electro-oxidation reaction. Electrochim Acta 53 6149-6156. 

Os and Ru bis(terpyridine) complexes have been covalently linked (Figure 13) and their electrochemical, absorption spectra, photochemical and photophysical properties have been studied. The strong electronic interaction decreases as the one or two phenylene spacers are added but remains large enough to allow fast electron transfer. ... 

The occurrence of energy transfer requires electronic interactions and therefore its rate decreases with increasing distance. Depending on the interaction mechanism, the distance dependence may follow a 1/r (resonance (Forster) mechanism) or e (exchange (Dexter) mechanisms) [ 1 ]. In both cases, energy transfer is favored by overlap between the emission spectrum of the donor and the absorption spectrum of the acceptor. 

H2 TDS was used as the highest H2 desorption temperature (370 K) occurs below the temperature regime of encapsulation. For the reduced sample there was a 70% decrease In H2 chemisorption and a 33 K shift to lower temperatures when the unannealed sample (first H2 TDS) was compared to the sample annealed at 370 K (second H2 TDS). No change In the AES was observed after either the first or second TDS, showing that the Pt overlayer does not Island or encapsulate. We take these low Pt coverage experiments to Indicate an electronic Interaction (preferably bond formation, which does not require significant charge transfer) between Pt and reduced Tl species that Is activated at about 370 K. 

The carrier-phonon interaction decreases with the lowering of temperature, since the emission and absorption of phonons by carriers is proportional to the number of final states available to carriers and phonons. At sufficiently low temperatures, the interaction between the two subsystems can be so weak that there is no thermal equilibrium between them, and the energy is distributed among electrons more rapidly than it is distributed to the lattice, resulting in a different temperature for electron and phonon subsystems, giving rise to the so-called electron-phonon decoupling . 

From the work reported in literature it can be thus concluded that there will be various forms of carbonaceous species, which vary in reactivity, that exist on the catalyst or support during FTS. Some forms of this carbon are active (atomic surface carbide and CHX species) and even considered as intermediate species in FTS. However, it is also clear that especially during extended runs there may be a build up/transformation to less reactive forms of carbon (e.g., polymeric carbon). The amounts of these species may be small, but depending on their location, they may be responsible for a part of deactivation observed on cobalt-based FTS catalysts. The electronic interaction of carbon with the catalyst surface may also result in decreased activity. 

The antiaromatic region is not important for the reactivity of the parent enediyne because the activation energy is determined only by the energy difference between the reactant and the TS. However, for the cyclic enediynes in Fig. 7 in which the C1-C6 distances are 3.39 and 2.92 A, respectively, antiaromaticity of the reactant should be relevant to the reaction kinetics. In addition, the role of repulsion between the in-plane filled orbitals is accentuated by a parallel decrease in the attractive two-electron interaction between the re and re orbitals which vanishes at the 3.2 A distance between the terminal carbon atoms. 

It has been known for some time that the basicities of a heteroatom decrease upon a-silyl substitution [12], For example, alkyl silyl ethers (R3Si-0-R ) are less basic than dialkly ethers. Silylamines are weak bases compared to alkylam-ines. This electron-withdrawing effect of silyl groups has been explained in terms of the interaction between low lying vacant orbitals such as 3d orbitals of silicon or a orbitals with the nonbonding p orbitals (lone pairs) of the heteroatom (Fig. 4). This interaction decreases the HOMO level which in turn lowers the basicity of the heteroatom. Such effect may also cause the increase of the oxidation potentials, but little study has been reported on the electrochemical properties of this type of compounds. 

Since the electronic interaction of the two reactants becomes more favorable with decreasing separation, the most favorable configuration for electron transfer is generally one in which the two reactants are in close proximity. Opposing this is the coulombic work required to bring similarly-charged reactants together, and ultimately the electron-electron... 

Our studies of electronic energy transfer reactions are consistent with a strong decrease in the electronic interaction matrix element in accordance with eq 2. However, these studies also indicate that at least two potentially distinguishable effects can result in constants larger than one might naively predict using eq 2 ... 

Like the Coulombic forces, the van der Waals interactions decrease less rapidly with increasing distance than the repulsive forces. They include interactions that arise from the dipole moments induced by nearby charges and permanent dipoles, as well as interactions between instantaneous dipole moments, referred to as dispersion forces (Israelachvili 1992). Instantaneous dipole moments can be thought of as arising from the motions of the electrons. Even though the electron probability distribution of a spherical atom has its center of gravity at the nuclear position, at any very short instance the electron positions will generally not be centered on the nucleus. 

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