Low temperature crystal and electronic band structure of the (BEDO–TTF)2Cl1.28(H3O)0.282.44H2O stable organic metal

Abstract

A bis(ethylenedioxy)tetrathiafulvalene (BEDO–TTF) chloride was synthesized by a combined diffusion-electrocrystallization method using the [(C₂H₅)₄N]₂CuCl₄ salt as supporting electrolyte. An X-ray analysis has been carried out at both room and low (160 K) temperatures: a=5.097(1), b=8.592(2), c=16.236(2) Å, α=98.13(1)^o , V=703.8 ų (293 K) and a=5.069(2), b=8.435(6), c=16.137(4) Å, α=97.82(4)^o , V=683.6 ų (160 K); space group P2₁ /b. This salt seems to be the same BEDO–TTF chloride previously reported by several groups although its composition was never firmly established. The crystal structure is characterized by the presence of Θ-type radical cation layers alternating along the c-direction with honeycomb-like polymeric networks including Cl^– anions, H₂O molecules and H₃O⁺ , hydroxonium ions. The band structure and Fermi surface for different electron transfers at both 160 and 293 K have been calculated. The combination of these results with IR spectral data and analysis of the physical properties led to the conclusion that the real composition of this salt is (BEDO–TTF)₂Cl_1.28(H₃O)_0.28 2.44H₂O.