Molecular charge transfer systems

The last system investigated by the deformation-potential method is a member of the large family of charge-transfer molecular crystals containing as anion the tetracyanoquinodimethane (TCNQ) molecule. The K TCNQ" salt as well as the other TCNQ crystals consist of columns of stacked TCNQ molecules coordinated by similar columns of the cations. The energy band structures of the stack have been calculated earlier with the help of Pariser-Parr-Pople parametrization of the unrestricted Hartree-Fock crystal-orbital method The last two columns of Table 9.10 show that this material behaves again as a normal... 

Aloisi, G., Cauzzo, G. and Mazzucato, U. (1967) Charge transfer complexes between iodine and aromatic aza compounds. III. Pyridine and derivatives. Trans. Faraday Soc., 1858-1862. Masaguer, J.R., Sousa-Alonso, A., Garcia-Vazquez, J. A. and Blanco, A. (1977) Charge-transfer molecular complexes. Interaction of iodine with dimethyl pyridines. Afinidad, 34,186-190. Bhaskar, K.R. and Singh, S. (1967) Spectroscopic studies of n-donor-n-acceptor systems pyridines. Spectrochim. Acta, Part A, 33A, 1155-1159. 

The ultimate approach to simulate non-adiabatic effects is tln-ough the use of a fiill Scln-ddinger wavefunction for both the nuclei and the electrons, using the adiabatic-diabatic transfomiation methods discussed above. The whole machinery of approaches to solving the Scln-ddinger wavefiinction for adiabatic problems can be used, except that the size of the wavefiinction is now essentially doubled (for problems involving two-electronic states, to account for both states). The first application of these methods for molecular dynamical problems was for the charge-transfer system... 

First of all, the reaction pathways shown in Scheme 1 involve the formation of charge transfer complexes (CTC) between olefin and Br2- The formation of molecular complexes during olefin bromination had been hypothesized often (ref. 2), but until 1985, when we published a work on this subject (ref. 3), complexes of this type had been observed only in a very limited number of circumstances, all of which have in common a highly reduced reactivity of the olefm-halogen system, i.e. strongly deactivated olefins (ref. 4), or completely apolar solvents (ref. 5) or very low temperatures (ref 6). 

Carrier generators in molecular conductors have been associated for a long time to a partial charge transfer between the HOMO (or LUMO) electronic band and other chemical species. These systems are known as two-component molecular conductors. Tetrathiofulvalene derivatives are versatile systems for the formation of molecular organic conductors due to their electron donor capacity by transferring one u-electron from the HOMO orbital, and to their planar shape that promotes their stacking as a consequence of the n-n orbital overlap. The electronic properties of these salts are essentially determined by the packing pattern of the donor molecules which, in turn, depends on the counter-ion. 

Adsorption of Reaction Components In many cases, adsorption of a reactant is one of the hrst steps in the electrochemical reaction, and precedes charge transfer and/or other steps of the reaction. In many cases, intermediate reaction products are also adsorbed on the electrode s snrface. Equally, the adsorption of reaction products is possible. The example of the adsorption of molecular hydrogen on platinum had been given earlier. Hydrogen adsorption is possible on the platinum electrode in aqueons solntions even when there is no molecular hydrogen in the initial system at potentials more negative than 0.3 V (RHE), the electrochemical reaction... 

The first example of a donor-acceptor molecular complex was noted in 1949 by Bensei and Hildebrand [137] in their studies involving charge transfer complexes between benzene and molecular iodine. Subsequently such complexes were studied by Mulliken [138] and now more recently have been used by Stoddart et al. [16,139] in designing novel self-assembling systems. 

May V, Kuhn O (2004) Charge and energy transfer dynamics in molecular systems. Wiley-VCH, Weinheim, New York... 

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