A high mobility (∼1.0cm2∕Vs) n-type organic field-effect transistor is devised in terms of the combination of semiconducting and metallic charge-transfer (CT) compounds, namely, DBTTF-TCNQ crystals as channels and TTF-TCNQ thin films as electrodes for carrier injections on top of the crystals. Comparison of the field-effect properties for devices with conventional electrode materials indicates the successful demonstration of the interface band engineering with use of the CT materials.

Reaction between cytosine, a nucleobase, in methanol and several 7,7,8,8-tetracyanoquinodimethane derivatives (R-TCNQ) in acetonitrile yielded three kinds of ionic solids; (I) insulators composed of methoxy-substituted R-TCNQ anions, (II) semiconducting fully ionic R-TCNQ radical anion salts, and (III) conductive partially ionic or mixed-valent R-TCNQ radical anion salts. Electronic and chemical structures of these products were characterized by optical and magnetic measurements, and structural and elemental analyses. Cation units in all products were found to be protonated cytosine species. Crystal structures were determined for methoxy-substituted anion salts (R = F 4 and H) in Group I and R-TCNQ radical anion salts (R = H and Et 2 ) in Group II with hemiprotonated cytosine pairs formed by triple self-complementary hydrogen bonds. They established one-dimensional hemiprotonated cytosine ribbons by double complementary hydrogen bonds. Hydrogen bonds between cytosine and R-TCNQ anions exhibited high potential to regulate molecular arrangements producing a segregated layered structure and uniform arrangement of R-TCNQ radical anion columns stable down to low temperature. The partially ionic salt of MeTCNQ in Group III exhibited metallic behavior and the highest conductivity of 10 þ1 S cm À1 so far observed for charge-transfer complexes based on biological molecules.Biological molecules such as proteins, enzymes, DNA, etc., establish well-defined and complicated self-assembling structures which are important factors in the exhibition of their biological functions. This feature of biological molecules has attracted much attention from the viewpoint of supramolecular chemistry and crystal engineering in recent study of molecule-based materials.2 In research for organic conductors, several attempts to investigate charge-transfer (CT) complexes based on a variety of biological molecules have been also undertaken.

Although neral [(Z)-3,7-dimethyl-2,6-octadienal] has been known as the alarm pheromone of Schwiebea elongata, reinvestigation of the pheromone resulted in recognition of another function as an attractant. The alarm pheromone activity was confirmed at a dose of one female equivalent of the hexane extract, whereas the attractant pheromone activity was observed at 0.1 female equivalent. Although no attractant activity was recovered in fractions of the silica gel (SiO 2) column eluate, the synthetic neral manifested both activities; the attractant activity at 3 ng and 1 ng with a convex dose-response relationship, and the alarm pheromone activity at 30 ng. A female contained 30.4 ng of neral on average and a male 0.7 ng on average. This is the first example among astigmatid mites demonstrating that a single mite compound emitted from the opisthonotal gland exhibits two pheromonal functions, alarm pheromone and also attractant, at different doses.

BEDT-TTF (ET) and cyananilic acid (H 2 CNAL) afforded charge transfer crystals by a diffusion method. The chemical formula of the complex was deduced based on all the information concerning the elemental, structural, electric, magnetic and optical analyses. The ET molecules form one-dimensional columnar stacks composed of twisted dimers with a face-to-face overlap (a'-type stack). The acid works as an oxidant and is deprotonated to form the monoanion, HCNAL 12 , which forms ribbon-like aggregation by means of hydrogenbonds. The ribbons form anion layers that sandwich the ET layer. The crystal is semiconductive with a room temperature conductivity of 0.20-0.83 Scm 21 and activation energy of 0.15 eV along the stacking direction, though the band calculation by the extended Hu ¨ckel method suggests a metallic nature, indicating strong electron-correlation in this system. The complex is a Mott insulator and its magnetic susceptibility is described by the one-dimensional S~1 2 antiferromagnetic Heisenberg chain model with J/k B ~252¡3 K.

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