Izumi Motoyama

Preparation, characterization and electric conductivity of CT adducts of crystalline poly(1,1′-ferrocenylene) with electron acceptors

Abstract Crystalline poly(1,1′-ferrocenylene) forms adducts with various electron acceptors such as iodine, 2,2′-(2,5-cyclohexadiene-1,4-diylidene)bis-propanedinitrile (TCNQ), and tetracyanoethylene (TCNE). Magnetic susceptibilities, color, and Mossbauer spectra of the adducts indicate partial oxidation of Fe(II) in poly(1,1′-ferrocenylene) to Fe(III). The adducts of crystalline poly(1,1′-ferrocenylene) with the electron acceptors show much higher electric conductivities (by a factor of 102–106) than the previously reported adducts of amorphous poly(1,1′-ferrocenylene). Among the adducts studied, a TCNQ adducts shows the highest electric conductivity; σ = 4.1 X 10−2 S cm−1 for a 1:0.64 adduct of the polymer with TCNQ at 295 K. An X-ray diffraction pattern of the crystalline poly(1,1′-ferrocenylene) shows peaks at 11.8°, 19.2°, 23.5°, and 25.2°, whereas the TCNQ adducts gives rise to new sharp peaks at quite different positions. In contrast to a high crystallinity of the TCNQ adduct, the adducts of other electron acceptors are amorphous as revealed by their X-ray diffraction patterns which show no peaks. Both the peaks assigned to Fe(II) and Fe(III) found in the Mossbauer spectrum of the TCNQ adduct become broad on raising the temperature from 78 K to 310 K, suggesting the occurrence of a rapid intervalence electron exchange between Fe(II) and Fe(III) on the Mossbauer time scale at higher temperatures.