Energy Spectra and Electric and Magnetic Properties of 1D Stacks of Conjugated π-Electron Systems with Defect Surface States. I. π Systems with Tamm Surface States

Abstract

The energy spectra and the electric and magnetic properties of one-dimensional (1D) stacks consisting of conjugated π-electron systems (polycyclic aromatic hydrocarbons and polymethines) with Tamm defects are investigated theoretically by means of the many-electron band theory. The conditions for the relative arrangement of the stacks in terms of the slip parameters for yielding different magnetic and electric ground-state properties are studied.

Magnetic Properties of Langmuir–Blodgett (LB) Films: A Theoretical Study. III. LB Films Consisting of Different Types of Stable π-Monoradicals

“…Exchange integrals J eff,b have small values, and it could be expected that the LB films of C radicals consist of FM 1-D Heisenberg chains. The results obtained for LB films (with D = 1) with the same geometry parameters differs only quantitatively in comparison with these obtained for MRCs. ,− For the LB films of C radicals we obtain, according to the Ising model, the highest T c in this work of 256 K. Therefore, we further suggest a detailed experimental investigation of the L and LB films composed of galvinoxyl radicals as feasible high-temperature purely organic 2-D ferromagnets.…”

“…Because the PAHs have a pronounced hydrophobic character, only LB films of type B (see Figure ) are feasible. However, the results must be similar to the 1-D models investigated in the refs , , and .…”

“…The calculations for the components of J eff have been carried out using a standard set of parameters . Further details on the calculation of the overlap, resonance, and two-center integrals can be found in refs and − ; here we only give a short explanation for each of them. The dependence of the resonance integrals between neighboring carbon atoms within the EU on the bond lengths R has been calculated with Mulliken’s formula: β ( R , Θ ) = β 0 [ S false( R , normalΘ false) ] / S 0 nobreak0em0.25em⁡ cos nobreak0em.25em⁡ normalΘ where S are the overlap integrals between 2p–2p AOs (calculated with Z C = 3.25, Z N = 3.90, Z O = 4.55).…”

“…There are different types of defects in a PAH: − Tamm, Schottky, and chemisorption defects. The Weitz type monoradicals (see Figure ) are examples of hydrocarbons with impurity Tamm defects.…”

“…1-D stacked systems of such PAH with well-defined macroscopic architecture, crystals, and columnar discotic materials , determine the interest to these classes of hydrocarbons with corresponding defects. The magnetic properties of 1-D stacks consisting of polycyclic aromatic hydrocarbons with Tamm, Schottky, or chemisorption defects are investigated theoretically in refs , , and . In Figure is shown an example with a hydrocarbon with Tamm defect.…”