Creation of conductive supramolecular frameworks tailored by anisotropic intermolecular interactions and development of multi-functional materials

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It is well known that the variety of crystal and electronic structures in organic conductors depends not only on the structure of an individual molecule but also on the molecular arrangement in the crystal. We have proposed the introduction of strong and directional I・・・N type intermolecular interactions ("iodine bond") to organic conductors for the sake of crystal engineering.i) The known method for the syntheses of TTF-vinylogues based on the Wittig-type reaction includes multi-step syntheses of the starting materials. We have developed a new and simple method for the synthesis of iodine-bonded TTF-vinylogues. This direct coupling reaction of thione and aldehyde proceeds smoothly regardless of the substituent. We have obtained a series of novel iodine-bonded TTF-vinylogues.ii) Thermal behavior of a unique hexagonal system based on the iodine-bonded diselenedithiafulvalene "DIPS" has been studied. The channel structure is similar to those of the inorganic "zeolite" systems and it would be promising to introduce a variety of guest molecules to obtain multi-functional materials.iii) We have prepared a novel supramoleeular organic conductor θ-(DIETS)2[Au(CN)_4] and measured the temperature dependence of the electrical resistivity under the uniaxial strain. Superconducting transition was observed around 10 kbar and the onset temperature of the superconductivity has reached 8 K. It is the highest record among the known superconductors based on unsymmetrical organic π-donors. Furthermore, the effect of the uniaxial strain showed large anisotropy as expected.iv) We have prepared iodine-bonded tetraselenafulvalene (TSeF) derivatives without the use of highly toxic reagents H_2Se and CSe_2. A new organic conductor (DIETSe)>2AuCl_2 is metallic down to 4.2 K and its room temperature conductivity is up to 700 Scm<-1>. X-ray structure analysis has revealed that the unique supramolecular structure has been developed by the I・・・CI and l・・・Au strong iodine bond.