Acceptors molecules electron affinity

Acceptor molecule Electron affinity/eV A6/ppm Electron transfer /%... 

Photoelectron transfer is usually described by the so-called Foerster s cycle On transformation of a molecule into the excited state, the donor s IP is reduced by the value of the donor s excitation energy, and the acceptor s electron affinity increases by the value of the acceptor s excitation energy. 

Thus such a mild electron-acceptor molecules as p-benzoquinone (electron affinity 0.9 ev) and anthraquinone can, like the strong electron acceptor chloranil (electron affinity = 1.35 ev), abstract an electron from the ZnO, a semiconductor of the n-type. The abstracted electrons come from the local levels below and close to the conduction band, so that at room temperature they can migrate to the electron traps formed on the surface by the adsorbed electron acceptor. The accepting of an electron by the neutral quinone molecule, immediately leads to a redistribution of the valency bonds into the configuration of the anion radical (c). 

Fig. 10 Aviram-Ratner rectification via HOMO and LUMO. (a) A D-o-A molecule is sandwiched between two metal electrodes. MD is the electrode proximal to the donor, MA is the electrode proximal to the acceptor, is the electrode metal work function, IPD is the ionization potential of the donor, EAa is the electron affinity of the acceptor, (b) No pathway for current exists when a voltage is applied in the reverse bias direction, (c) Under a comparable voltage to (b) but in the forward bias direction, rectification results from electrons flowing from MA to LUMO to HOMO to MD...

It is now well established that when a surface presents electron donor or electron acceptor sites, it is possible to ionize molecules of relatively high electron affinity (> 2 eV) or low ionization potential values, resulting in paramagnetic radical ions. For instance anthracene and perylene are easily positively ionized on alumina (7 ) (IP = 7.2 and 6.8 eV respectively). The adsorption at room temperature of benzenic solution of perylene, anthracene and napthalene on H-ZSM-5 and H-ZSM-11 samples heated up to 800°C prior to adsorption did not give rise to the formation of the corresponding radical cation. For samples outgassed at high... 

Generally, it is the interaction of a donor (D) and an acceptor (A) involving the transfer of one electron. The probability of one-electron transfer is determined by thermodynamics namely, by the positive difference between the acceptor electron affinity and donor IP. The electron transfer is accompanied by a change in the solvate surroundings—charged particles are formed, and the solvent molecules (the solvent is usually polar) create a sphere around the particles thereby promoting their formation. Elevated temperatures destroy the solvate shell and hinder the conversion. Besides, electron transfer is often preceded by the formation of charge-transfer complexes by the sequence D A D A (D +, A -) (D+, A ) D+ A . ... 

For reproducing as closely as possible diabatic conditions, we have fixed the Cl—Cl bondlength at its neutral equilibrium value. This way, the system depends on two parameters as shown in Figure 1. Previous experimental and theoretical studies on similar systems, [1,18] have shown that electron jump from Li to the acceptor molecule CI2, which has, once relaxed, a positive vertical electron affinity (see Table 1), is likely to take place at a distance d, (see the definition of this parameter in Figure 1) which is superior to the LiCl equilibrium distance (MP2 value 2.0425 A). The description of this phenomenon in terms of MO and states will be briefly recalled in the next section. 

Structures. - A very comprehensive review of the literature on atomic and molecular electron affinities has been published142. The possibilities of per-fluoroaroinatic molecules as electron acceptors has been examined using a DFT... 

The electron transfer in the excited state is reversed when the molecule returns to the ground state, the leuco dye being oxidized back by ferric ion. A similar system includes mixed inorganic solutions such as (I2/I ) + (Fes+/Fe2+). In such electron transfer reactions, the acceptor has a much lower electron affinity in the ground state than the donor. Thus, the... 

When the quencher contains heavy atoms nonradialive relaxation of the exciple occurs via the triplet state (heavy atom perturbation). A second mode of exciplex dissociation is through electron transfer between the excited molecule and the quencher. Ionization potential of the donor, electron affinity of the acceptor and solvent dielectric constant are important parameters in such cases. 

The simplest method for calculating the ionization potentials and the electron affinities is the 7T-HMO method. Such an evaluation is particularly suitable for the determination of the relative electron donor-acceptor properties of the molecules. The appropriate indices are the energies of the highest occupied molecular orbitals (HOMO) for the electron donor capacity and the energies of the lowest empty molecular orbitals (LEMO) for the electron acceptor abilities. These simple theoretical predictions gave an excellent interpretation1,256 of the... 

The ability of molecules to form donor-acceptor complexes depends not only on their ionization potential, electron affinity and polarizability, but also on the requirements and properties of partners. 

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