Properties of viologen-TCNQ (2-2) Langmuir-Blodgett films

In conducting systems based on Langmuir-Blodgett(LB) films, TCNQ derivatives have been extensively studied as electron acceptor molecules. We have investigated the optical, electrical, and magnetic properties of viologen-(TCNQ)₂ LB films. In UV/visible absorption measurements, we have observed a TCNQ peak at 381 nm and a dimer peak at 626 nm. Iodine doping affects the degree of charge transfer and increases the conductivity of the films. The UV/visible absorption spectra of the LB film doped with I₂ show a peak at 400~430 nm and there is no dimer absorption peak. Electron spin resonance (ESR) measurements suggest that the viologen-(TCNQ)₂ LB film exhibits an anisotropic property, i.e. the ESR signal shows angular dependence. The in-plane electrical conductivity of the undoped film is approximately 4.3×10^-6 S/cm at room temperature