Double Layer Conducting Salts: (CNB-EDT-TTF)<sub>4</sub>X, X = ClO<sub>4</sub><sup>−</sup>, ReO<sub>4</sub><sup>−</sup>, and SbF<sub>6</sub><sup>−</sup>; Electrical Transport and Infrared Properties
Two new members of the family of bilayer compounds (CNB-EDT-TTF)<sub>4</sub>X, (CNB-EDT-TTF = <i>5</i>-cyanobenzene-ethylenedithio-tetrathiafulvalene) with anions X = ReO<sub>4</sub><sup>−</sup> and SbF<sub>6</sub><sup>&...
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doaj-d6c50be9823f4e3c8efbae10b7ff0cfa2020-11-25T02:21:30ZengMDPI AGCrystals2073-43522019-11-0191260810.3390/cryst9120608cryst9120608Double Layer Conducting Salts: (CNB-EDT-TTF)<sub>4</sub>X, X = ClO<sub>4</sub><sup>−</sup>, ReO<sub>4</sub><sup>−</sup>, and SbF<sub>6</sub><sup>−</sup>; Electrical Transport and Infrared PropertiesSandrina Oliveira0Ana Cristina Gonçalves1Gonçalo Oliveira2Dominik Günther3Andrea Rohwer4Vasco Gama5Elsa Branco Lopes6Isabel Cordeiro Santos7Sandra Rabaça8Manuel Almeida9Martin Dressel10C2TN, Instituto Superior Técnico, Universidade de Lisboa, Estrada Nacional 10, P-2695-066 Bobadela LRS, PortugalC2TN, Instituto Superior Técnico, Universidade de Lisboa, Estrada Nacional 10, P-2695-066 Bobadela LRS, PortugalC2TN, Instituto Superior Técnico, Universidade de Lisboa, Estrada Nacional 10, P-2695-066 Bobadela LRS, PortugalPhysikalisches Institut, Universität Stuttgart, Pfaffenwaldring 57, D-70550 Stuttgart, GermanyPhysikalisches Institut, Universität Stuttgart, Pfaffenwaldring 57, D-70550 Stuttgart, GermanyC2TN, Instituto Superior Técnico, Universidade de Lisboa, Estrada Nacional 10, P-2695-066 Bobadela LRS, PortugalC2TN, Instituto Superior Técnico, Universidade de Lisboa, Estrada Nacional 10, P-2695-066 Bobadela LRS, PortugalC2TN, Instituto Superior Técnico, Universidade de Lisboa, Estrada Nacional 10, P-2695-066 Bobadela LRS, PortugalC2TN, Instituto Superior Técnico, Universidade de Lisboa, Estrada Nacional 10, P-2695-066 Bobadela LRS, PortugalC2TN, Instituto Superior Técnico, Universidade de Lisboa, Estrada Nacional 10, P-2695-066 Bobadela LRS, PortugalPhysikalisches Institut, Universität Stuttgart, Pfaffenwaldring 57, D-70550 Stuttgart, GermanyTwo new members of the family of bilayer compounds (CNB-EDT-TTF)<sub>4</sub>X, (CNB-EDT-TTF = <i>5</i>-cyanobenzene-ethylenedithio-tetrathiafulvalene) with anions X = ReO<sub>4</sub><sup>−</sup> and SbF<sub>6</sub><sup>−</sup> are reported, their electron transport and optical properties investigated, and then compared to the ClO<sub>4</sub><sup>−</sup> salt that was previously described. These compounds share the same structural type, i.e. bilayers of donors, which are packed in a β”-type pattern and then separated by layers of highly disordered anions. The absolute values of the electrical resistivity measured in single crystals within the layers were found in the range of 5 to 18 (cm)<sup>−</sup><sup>1</sup>, with a significantly sample dependence being ascribed to intrinsic disorder effects. The ClO<sub>4</sub><sup>−</sup> and SbF<sub>6</sub><sup>−</sup> salts exhibit metallic behavior with the resistivity decreasing upon cooling almost linearly with temperature until a broad minimum is reached between 15 and 80 K, depending on crystal quality; this is followed by an upturn of resistivity reaching values at T = 1.5 K that were comparable to those attained at room temperature. The electrical resistivity of the ReO<sub>4</sub><sup>−</sup> salt follows a thermally activated behavior already at T = 300 K, although with a small activation energy in the range 16−18 meV. Thermoelectric power measurements yield large positive values (75−80 µV/K) at ambient temperature with a metallic behavior that is identical for all compounds. Temperature and polarization dependent infrared reflection measurements on single crystals of (CNB-EDT-TTF)<sub>4</sub>X salts, with X = ClO<sub>4</sub><sup>−</sup>, ReO<sub>4</sub><sup>−</sup>, and SbF<sub>6</sub><sup>−</sup>, have been performed to obtain the optical conductivity and analyze the electronic and vibrational properties. For (CNB-EDT-TTF)<sub>4</sub>ClO<sub>4</sub> the molecular vibrations exhibit a significant variation below T = 23 K, which suggests a charge localization phenomena.https://www.mdpi.com/2073-4352/9/12/608two-dimensional molecular metalsbilayer structureelectrical resistivitythermoelectric poweroptical conductivityir spectra |
collection |
DOAJ |
language |
English |
format |
Article |
sources |
DOAJ |
author |
Sandrina Oliveira Ana Cristina Gonçalves Gonçalo Oliveira Dominik Günther Andrea Rohwer Vasco Gama Elsa Branco Lopes Isabel Cordeiro Santos Sandra Rabaça Manuel Almeida Martin Dressel |
spellingShingle |
Sandrina Oliveira Ana Cristina Gonçalves Gonçalo Oliveira Dominik Günther Andrea Rohwer Vasco Gama Elsa Branco Lopes Isabel Cordeiro Santos Sandra Rabaça Manuel Almeida Martin Dressel Double Layer Conducting Salts: (CNB-EDT-TTF)<sub>4</sub>X, X = ClO<sub>4</sub><sup>−</sup>, ReO<sub>4</sub><sup>−</sup>, and SbF<sub>6</sub><sup>−</sup>; Electrical Transport and Infrared Properties Crystals two-dimensional molecular metals bilayer structure electrical resistivity thermoelectric power optical conductivity ir spectra |
author_facet |
Sandrina Oliveira Ana Cristina Gonçalves Gonçalo Oliveira Dominik Günther Andrea Rohwer Vasco Gama Elsa Branco Lopes Isabel Cordeiro Santos Sandra Rabaça Manuel Almeida Martin Dressel |
author_sort |
Sandrina Oliveira |
title |
Double Layer Conducting Salts: (CNB-EDT-TTF)<sub>4</sub>X, X = ClO<sub>4</sub><sup>−</sup>, ReO<sub>4</sub><sup>−</sup>, and SbF<sub>6</sub><sup>−</sup>; Electrical Transport and Infrared Properties |
title_short |
Double Layer Conducting Salts: (CNB-EDT-TTF)<sub>4</sub>X, X = ClO<sub>4</sub><sup>−</sup>, ReO<sub>4</sub><sup>−</sup>, and SbF<sub>6</sub><sup>−</sup>; Electrical Transport and Infrared Properties |
title_full |
Double Layer Conducting Salts: (CNB-EDT-TTF)<sub>4</sub>X, X = ClO<sub>4</sub><sup>−</sup>, ReO<sub>4</sub><sup>−</sup>, and SbF<sub>6</sub><sup>−</sup>; Electrical Transport and Infrared Properties |
title_fullStr |
Double Layer Conducting Salts: (CNB-EDT-TTF)<sub>4</sub>X, X = ClO<sub>4</sub><sup>−</sup>, ReO<sub>4</sub><sup>−</sup>, and SbF<sub>6</sub><sup>−</sup>; Electrical Transport and Infrared Properties |
title_full_unstemmed |
Double Layer Conducting Salts: (CNB-EDT-TTF)<sub>4</sub>X, X = ClO<sub>4</sub><sup>−</sup>, ReO<sub>4</sub><sup>−</sup>, and SbF<sub>6</sub><sup>−</sup>; Electrical Transport and Infrared Properties |
title_sort |
double layer conducting salts: (cnb-edt-ttf)<sub>4</sub>x, x = clo<sub>4</sub><sup>−</sup>, reo<sub>4</sub><sup>−</sup>, and sbf<sub>6</sub><sup>−</sup>; electrical transport and infrared properties |
publisher |
MDPI AG |
series |
Crystals |
issn |
2073-4352 |
publishDate |
2019-11-01 |
description |
Two new members of the family of bilayer compounds (CNB-EDT-TTF)<sub>4</sub>X, (CNB-EDT-TTF = <i>5</i>-cyanobenzene-ethylenedithio-tetrathiafulvalene) with anions X = ReO<sub>4</sub><sup>−</sup> and SbF<sub>6</sub><sup>−</sup> are reported, their electron transport and optical properties investigated, and then compared to the ClO<sub>4</sub><sup>−</sup> salt that was previously described. These compounds share the same structural type, i.e. bilayers of donors, which are packed in a β”-type pattern and then separated by layers of highly disordered anions. The absolute values of the electrical resistivity measured in single crystals within the layers were found in the range of 5 to 18 (cm)<sup>−</sup><sup>1</sup>, with a significantly sample dependence being ascribed to intrinsic disorder effects. The ClO<sub>4</sub><sup>−</sup> and SbF<sub>6</sub><sup>−</sup> salts exhibit metallic behavior with the resistivity decreasing upon cooling almost linearly with temperature until a broad minimum is reached between 15 and 80 K, depending on crystal quality; this is followed by an upturn of resistivity reaching values at T = 1.5 K that were comparable to those attained at room temperature. The electrical resistivity of the ReO<sub>4</sub><sup>−</sup> salt follows a thermally activated behavior already at T = 300 K, although with a small activation energy in the range 16−18 meV. Thermoelectric power measurements yield large positive values (75−80 µV/K) at ambient temperature with a metallic behavior that is identical for all compounds. Temperature and polarization dependent infrared reflection measurements on single crystals of (CNB-EDT-TTF)<sub>4</sub>X salts, with X = ClO<sub>4</sub><sup>−</sup>, ReO<sub>4</sub><sup>−</sup>, and SbF<sub>6</sub><sup>−</sup>, have been performed to obtain the optical conductivity and analyze the electronic and vibrational properties. For (CNB-EDT-TTF)<sub>4</sub>ClO<sub>4</sub> the molecular vibrations exhibit a significant variation below T = 23 K, which suggests a charge localization phenomena. |
topic |
two-dimensional molecular metals bilayer structure electrical resistivity thermoelectric power optical conductivity ir spectra |
url |
https://www.mdpi.com/2073-4352/9/12/608 |
work_keys_str_mv |
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