Singly occupied molecular orbital polymers

Fig. 11.10. Three-dimensional representation of the singly occupied molecular orbital (SOMO) for the quinquepyrrole. (Reprinted with permission from D. J. Fermin, M. Mostany, and B. Scharifker, Electronically Conducting Polymers Synthesis and Electrochemical Properties of Polypyrrole, Curr. Topics Electrochem. 2 132-136, 1993.)...

In principle, molecules can be either passive or active electronic components, either singly or in parallel as a one-molecule-thick monolayer array. This may lead to electronic devices with dimensions of 1-3 nm. Unimolecular electronics (UE) or molecular electronics sensu stricto, or molecular-scale electronics evolved from studies of organic crystalline metals, superconductors, and conducting polymers the idea is to exploit the electronic energy levels of a single molecule, and most importantly its HOMO (highest occupied molecular orbital) and LUMO (lowest unoccupied molecular orbital), which can be tuned, or modified by incorporation of electron-donating... 

Such polymers might be of substantial technological interest as electrically conductive molecular wires. Density functional (DFT) calculations indicated that the metal-based HOMO of 26 is delocalized across all four of the central copper(I) ions, as shown in Figure 1.6. Calculations also indicate that removal of one electron from this HOMO likewise results in a fully delocalized singly occupied orbital. This delocalization could provide a path for conductivity, allowing an electric current to flow from one end of a helicate polymer strand to the other. 

The standard theory in molecules and polymers is based on the Hartree-Fock theory. In this model, a single electron moves in the field of the nuclei and in the mean Coulomb and exchange field of all the other electrons. A set of molecular orbitals (MOs) is obtained to describe the occupied and unoccupied one-electron wave functions. In molecular quantum chemistry, the molecular orbitals are drawn as single levels, which are at most doubly occupied by a pair of electrons of opposite spin. On the other hand,... 

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