Ambient-pressure organic superconductors κ-(DMEDOTSeF) 2[Au(CN)4](Solv.): Tc tuning by modification of the solvent of crystallization

Abstract

The unsymmetrical π donor dimethyl(ethylenedioxy)tetraselenafulvalene (DMEDO-TSeF) has provided six new organic superconductors with a monovalent square-planar [Au(CN)4] ion and cyclic ethers as solvent of crystallization. The six new organic superconductors κ-(DMEDOTSeF) 2[Au(CN)4](Solv.) [solv. = 1,3-dioxolane (DOL), 2,5-dihydrofuran (DHF), tetrahydropyran (THP), 1,3-dioxane (1,3-DOX), 3,4-dihydro-2Hpyran (DHP), or 1,4-dioxane (1,4DOX)] are classified into two subphases κL and κ′ according to the differen ces in their space group symmetry. κL(DMEDO-TSeF) 2[Au(CN)4](Solv.) (solv. = DOL, DHF, THP, 1,3-DOX or DHP) crystallizes in the orthorhombic space group Prima, and Tc of the κL phase varies by 1.7-5.3 K according to the size and shape of the solvent of crystallization. On the other hand, κ′ (DMEDO-TSeF)2[Au(CN)4](Solv.) (solv. = DOL or 1,4-DOX) crystallizes in the noncentrosymmetric monoclinic space group Cc. The κ′-phase containing 1,4-DOX shows superconductivity at 4.2 K, but the κ′-phase containing DOL does not show superconductivity down to 1.4 K. Systematic investigation of the six new organic superconductors, together with the two previously reported superconductors κH- and κL(DMEDO-TSeF)2[Au(CN)4](THF), revealed that the Tc of the present system is finely tunable by utilizing the effect of the solvent of crystallization. © 2007 Wiley-VCH Verlag GmbH & Co. KGaA.