Electronic structure of conjugated

Both theoretical and experimental evidence suggest that the precise nature of the charge carriers in conjugated polymer systems varies from material to material, and it is still a subject of debate in many cases. A discussion of the various theoretical models for the electronic structure of conjugated polymers is given below, using polyacetylene and poly(paraphenylene) as examples. More detailed information on these materials and the applicability of these theoretical models is given in subsequent sections. 

Bredas J-L, Comil J, Beljonne D, Santos DAD, Shuai Z (1999) Excited-state electronic structure of conjugated oligomers and polymers a quantum-chemical approach to optical phenomena. Acc Chem Res 32 267-276... 

Dobrosavljevic V, Stratt R (1987) Role of conformational disorder in the electronic-structure of conjugated polymers substituted polydiacetylenes. Phys Rev B 35 2781-2794... 

RECURRENT VARIATIONAL APPROACH APPLIED TO THE ELECTRONIC STRUCTURE OF CONJUGATED POLYMERS... 

To conclude, we have presented in this note the Recurrent Variational Approach and, more specifically, its first application to the electronic structure of conjugated polymers. The ansatz built here (26), shows some nice similarities with the trial state (3) made for the two-leg ladder. 

Recurrent variational approach applied to the electronic structure of conjugated polymers 169... 

Coulson, C.A. and Longuett-Higgins, H.C., The electronic structure of conjugated systems. I. General theory, Proc. R. Soc. (London) A, 191, 39-60, 1947. 

In this section the electronic structure of conjugated polymers is discussed. They form a special class of materials with particular types of excitations (such as the solitons) and properties, introduced briefly in Chapter 11. These problems are discussed here essentially in relation to the spectroscopic properties. The related but distinct subject of electrical conductivity is treated in Section IV. To set the scene, we first present some typical results visible absorption and emission spectra and resonance Raman spectra. We consider the theoretical issues in Section III.B, then return to the meaning of the experimental results in Section III.C. The interesting nonlinear optical properties of CPs will be considered in Section III.D. These sections are concerned with electronic states within the gap or near the band edges the structure (i.e., the dispersion relations) of valence and conduction bands is also of theoretical interest and is considered in Section III.E. 

A 7i-conjugated systems is a molecule along the backbone of which occurs a continuous path of carbon atoms or heteroatoms, each carrying a p atomic orbital. The determination of the electronic structure of conjugated systems and their properties in terms of energy, electron and hole transport is very difficult. Electron correlation effects must be taken into account and the strong connection between, and mutual influence of, the electronic and geometric structures should be evaluated [91]. 

The Coulson Rushbrooke theorems have many important consequences that will lead us a long way towards a qualitative understanding of the electronic structure of conjugated molecules, particularly of their excited states. Dewar developed a simple perturbation method PMO theory) to evaluate the HOMO LUMO gap and the associated excitation energy for 7t-systems with an even number of conjugated atoms.284,285,288 Because the NBMO of odd AHs can be determined so easily, the system of interest is dissected into two odd AHs. Some examples are shown in Scheme 4.1. 

The electronic structure of conjugated polymer semiconductors reflects the complex interplay between intrinsic rr-electron delocalization along the polymer backbone and strong electron-phonon coupling, and the existence of energetic and positional disorder in solution-processed thin films. In a hypothetical, infinitely straight polymer chain, the highest occupied molecular orbital (HOMO) and lowest unoccupied... 

In the development and fabrication of molecular-based electronics, it is essential to have a good understanding of the chemistry and electronic struemre of the electroactive polymer interface with other polymers, semi-conductors and metals. A better understanding of the CT interactions at the polymer/metal interface will also facilitate the application of conductive polymer coatings for metal passivation and corrosion prevention [268]. An overview of measurement methods and quantum chemical calculation techniques for smdying the chemical and electronic structure of conjugated... 

Li, L. Collard, D.M. Tuning the electronic structure of conjugated polymers with fluoroalkyl substitution alternating alkyl/perfluoroalkyl-substituted polythiophene. Macromolecules 2005, 38, 372-378. 

W. R. Salaneck, R. H. Friend, J. L. Br das, Electronic Structure of Conjugated Polymers Consequences of Electron-Lattice Coupling. Phys. Rep. 1999,319, 231-251. 

Coulson, C. A., Longuet-Higgins, H. C. (1947). The Electronic Structure of Conjugated Systems. II. Unsaturated Hydrocarbons and their Hetero-Derivatives. Proceedings of the Royal Society of London A Mathematical, Physical and Engineering Sciences, 792(1028), 16-32. 

FIGURE 1.6 Schematic representation of the electronic structure of conjugated polymers according to (a) hand theory and (b) a molecular picture. 

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