Charge-Transfer Salts Derived from the New Electron-Donor Molecule BEDO-TTF: ESR, Superconductivity and Electrical Properties, and Crystal and Band Electronic Structure

Abstract

Abstract Charge transfer salts of bis(ethylenedioxy)tetrathiafulvalene, BEDO-TTF, namely (BEDO-TTF)2AuBr2, and charge transfer salts (BEDO-TTF)mXn where X− is I3, AuI2 −, Au(CN)2−, ClO4 −, BrO4 −, BF4 −, PF6 −, AsF6 −, NO3 −, C(CN)3 −, and HgBr3− have been synthesized. The AuBr2− salt is the first BEDO-TTF salt to be structurally characterized. Crystallographic investigations of several of the other (BEDO-TTF)mXn salts have shown that (with the exception of the I3− salt) these new synmetals are structurally very similar to (BEDO- TTF)2AuBr2. Therefore, a 2:1 stoichometry is expected for BEDO-TTF salts. The observation of similar ESR linewidths for all the BEDO-TTF salts reinforces this conclusion. While (BEDO-TTF)2PF6 is semiconducting and the AuBr2−, Au(CN)2−, and ClO4− salts are metallic only near room temperature and semiconducting at low temperatures, (BEDO-TTF)2AuI2 shows metallic conductivity to low temperatures. RF penetration depth measurements on crystals derived from BEDO-TTF/KSCN/CuSCN show the occurence of superconductivity near 1 K. Band electronic structure calculations on (BEDO-TTF)2AuBr2 and (BEDO-TTF)2ClO4 indicate that they are one-dimensional metals.