Polymorphism and Superconductivity in Bilayer Molecular Metals (CNB-EDT-TTF)4I3.
Inorg Chem
; 55(20): 10343-10350, 2016 Oct 17.
Article
em En
| MEDLINE
| ID: mdl-27681055
ABSTRACT
Electrocrystallization from solutions of the dissymmetrical ET derivative cyanobenzene-ethylenedithio-tetrathiafulvalene (CNB-EDT-TTF) in the presence of triiodide I3- affords two different polymorphs (ßâ³ and κ) with the composition (CNB-EDT-TTF)4I3, both with a bilayer structure of the donors. These polymorphs differ in the packing patterns (ßâ³- and κ-type) of the donor molecules in each layer, in both cases with bifurcated C-N···H interactions effectively coupling head-to-head donor molecules between layer pairs. Two ßâ³ polymorphs can be obtained with different degrees of anionic ordering. In one disordered phase, ßâ³d, with a smaller unit cell, the triiodide anions are disordered over two possible positions in a channel between the donor bilayers, while in the ordered phase, ßâ³o, the triiodide anions occupy only one of those positions in this channel, leading to the doubling of the unit cell in the layer plane. These results for ßâ³ phases contrast with the κ polymorph previously reported, for which weaker disorder of the triiodide anions, over two possible orientations with 94 and 6% occupation factors, was observed. While the ßâ³ polymorphs remains metallic down to 1.5 K with a ρ300K/ρ4K resistivity ratio of 250, the κ polymorph presents a much smaller resistivity ratio in the range of 4-10 and superconductivity with an onset temperature of 3.5 K.
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MEDLINE
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En
Ano de publicação:
2016
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Article