Hybrid Organic/Inorganic Supramolecular Conductors D₂[Au(CN)₄] [D = Diiodo(ethylenedichalcogeno)tetrachalcogenofulvalene], Including a New Ambient Pressure Superconductor

Abstract

Abstract Five diiodo(ethylenedichalcogeno)tetrachalcogenofulvalenes, DIEDSS {2‐(5,6‐dihydro[1,3]diselenolo[4,5‐ b ][1,4]diselenin‐2‐ylidene)‐4,5‐diiodo‐1,3‐dithiole}, DIET‐STF {2‐(4,5‐diiodo‐1,3‐diselenol‐2‐ylidene)‐5,6‐dihydro[1,3]dithiolo[4,5‐ b ][1,4]dithiine}, DIEDS‐STF {2‐(4,5‐diiodo‐1,3‐diselenol‐2‐ylidene)‐5,6‐dihydro[1,4]diselenino[2,3‐ d ][1,3]dithiole}, DIETSe {2‐(4,5‐diiodo‐1,3‐diselenol‐2‐ylidene)‐5,6‐dihydro[1,3]diselenolo[4,5‐ b ][1,4]dithiine}, and DIEDSSe {2‐(4,5‐diiodo‐1,3‐diselenol‐2‐ylidene)‐5,6‐dihydro[1,3]diselenolo[4,5‐ b ][1,4]diselenine},have been synthesized without the use of the highly toxic reagent CSe 2 , and their Au(CN) 4 salts have been prepared by electrochemical oxidation. Characteristic I ··· N iodine bonds are constructed in all crystals, and their packing motifs are classified into two groups by the difference in the space group symmetry. The salt of DIEDSS crystallizes in the monoclinic C 2/ c space group and a novel helical supramolecular architecture is constructed by the strong and directional I ··· N iodine bond. On the other hand, the rest of the four salts crystallize in the triclinic P $\bar {1}$ space group and their donor packing motifs belong to the so‐called β‐type. Conducting properties of the β‐type salts strongly depend on the number and positions of the selenium atoms on the donor molecule. The salts based on the diselenadithiafulvalene (DSDTF) derivatives, DIET‐STF and DIEDS‐STF, show metal–semiconductor transition and the salt of fully selenated π‐donor DIEDSSe shows stable metallic behavior down to 1.6 K. On the other hand, (DIETSe) 2 [Au(CN) 4 ] is semimetallic down to low temperature and the superconducting transition occurs at around 2 K (onset).(© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007)