Molecular conductors containing photoreactive species

Abstract

In order to examine the possibility of (persistent) carrier doping to molecular crystals by light exposure, some different types of molecular crystals containing photoreactive species are synthesized and characterized. The [Ru(bpy) 3 ] 2+ cation (bpy = 2,2'-bipyridyl) yielded two different new complexes with [Ni(dmit) 2 ]radical species, both of which were structurally characterized and turned out to be band insulators. Methy viologen (MV) has been found to yield a new phase of the complex with [Ni(dmit) 2 ]-, MV[Ni(dmit) 2 ] 2. The temperature dependences of electrical resistivity (decreasing with lowering temperature down to 1.0 K) and magnetic susceptibility (Pauli paramagnetism from 300 K to 1.8 K with a hysteresis below ~ 100 K) clearly indicate that this phase is metallic. The thermoelectric power exhibited ~0 µVK-1 from 300 K-4.2 K. This phase turned out to be metastable, and the crystals gradually turned into insulating ones. The effects of UV-VIS light exposure to the conducting and magnetic properties of Ag(DMe-DCNQI) 2 have been studied, and clear differences between the exposed and the pristine crystals were observed. The ESR signal at 3.7 K suggested that the exposed sample should include the Ag(0) species.

Direct Formation of Micro-/Nanocrystalline 2,5-Dimethyl-N,N‘-dicyanoquinonediimine Complexes on SiO2/Si Substrates and Multiprobe Measurement of Conduction Properties

“…In addition to this apparent transition at 100 K, a slight and gradual increase in resistance at 260−290 K dependent on the duration of exposure to light in the ultraviolet−visible regime has also been reported . This feature was also observed in the present experiments, as indicated by arrows in Figure .…”

Development of a Control Method for Conduction and Magnetism in Molecular Crystals

“…Thus a single crystal can be modified to have a junction structure ( Figure 4). 81,92,93 Junction structures are comprised of qualitatively different conduction parts, being a basic and necessary structure for all kinds of semiconductor devices. This treatment may correspond to the mixing of an insulator into the metal at a molecular level.…”

“…Next, in order to distinguish artifacts from intrinsic and reproducible phenomena, the irradiation conditions were widely varied ( Figures 6 and 7), 98 and all the resultant changes and products were examined and characterized one by one. 80,81,92,93,98107 If we call the starting material α, the irradiated products from various conditions were classified into four different compounds called β, γ, δ and ε. The products are summarized in Figure 6 with their chemical formulae and typical irradiation conditions for production from α (Table 1).…”