The ESR Study on Langmuir-Blodgett Films Layered with Ammontum-TCNQ Anion Radical Salts

Abstract

Ammonium TCNQ anion radicals are formed with a TCNQ anion radical and an ammonium halide. Octadecylviologen-(TCNQ)₂ shows a very interesting UV-visible spectrum in chloroform-acetonitrile mixture and in Langmuir-Blodgett films. The ESR characteristics of the N-docosylquinolinium-TCNQ films and octadecylviologen-(TCNQ)₂ powder and films were studied to understand conducting mechanism and structure of LB films. The ESR spectra infer that the N-docosylquinolinium-TCNQ LB films exhibit anisotropic property. In other words, the LB films show angular dependence. Rotating the LB films around magnetic field results in a minimum band width at an angle close to the magic angle 54°. This results was due to the dipole-dipole interaction. The ESR spectra of octadecylviologen-(TCNQ)₂ powders exhibit a narrow line at g=2 together with symmetrical structure of a triplet state arising from a dimeric species, genetic species. The LB films and powder do not show angular dependence. In the course of temperature increase from 350 to 450K, the ESR signal of LB films becomes sharp. But powder octadecylviologen-(TCNQ⁻)₂ does not have angular dependence.