β”-(CNB-EDT-TTF)4BF4; Anion Disorder Effects in Bilayer Molecular Metals
The preparation and characterization of new salts based on the dissymmetrical TTF derivative CNB-EDT-TTF (cyanobenzene-ethylenedithio-tetrathiafulvalene) and BF4− anions, are reported. Depending on the electrocrystallization conditions salts with different stoichiometries, (CNB-EDT-TTF)BF4 and β”-(C...
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| Format: | Article |
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MDPI AG
2018-03-01
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| Series: | Crystals |
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| Online Access: | http://www.mdpi.com/2073-4352/8/4/142 |
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| author | Sandra Rabaça Sandrina Oliveira Vasco Gama Isabel C. Santos Gonçalo Oliveira Elsa B. Lopes Enric Canadell Manuel Almeida |
| author_facet | Sandra Rabaça Sandrina Oliveira Vasco Gama Isabel C. Santos Gonçalo Oliveira Elsa B. Lopes Enric Canadell Manuel Almeida |
| author_sort | Sandra Rabaça |
| collection | DOAJ |
| description | The preparation and characterization of new salts based on the dissymmetrical TTF derivative CNB-EDT-TTF (cyanobenzene-ethylenedithio-tetrathiafulvalene) and BF4− anions, are reported. Depending on the electrocrystallization conditions salts with different stoichiometries, (CNB-EDT-TTF)BF4 and β”-(CNB-EDT-TTF)4BF4, can be obtained. The 1:1 salt is an electrical insulator isostructural to the ClO4 analogue previously described. The 4:1 salt is a new member of the family of 2D metals of this donor with different small anions X, (CNB-EDT-TTF)4X, characterized by a bilayer arrangement of the donors and it was obtained in a monoclinic polymorph with a β”-type donor packing pattern. The small anions in this compound are severely disordered between the donor bilayers, which present slightly larger lattice parameters than the isostructural ClO4 analogue. Both electrical conductivity and thermoelectric power measurements in single crystals denote metallic properties as predicted by electronic band structure calculations. As a consequence of the anion disorder the metallic regime of the electrical conductivity denotes electronic localization effects with a progressive increase of resistivity below ~25 K. Because of the larger lattice parameters the intermolecular interactions and electronic bandwidth are decreased compared to other (CNB-EDT-TTF)4X salts. The large and positive thermoelectric power S of this compound (~110 μV/K in the range 100–330 K) and its electrical conductivity σ = 20 S/cm at room temperature lead to a power factor S2σ = 24 μW/K2m, quite large among molecular conductors, placing these compounds as potential candidates for thermoelectric materials. |
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| language | English |
| last_indexed | 2024-04-12T19:30:26Z |
| publishDate | 2018-03-01 |
| publisher | MDPI AG |
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| series | Crystals |
| spelling | doaj.art-5363f4fe9a154590b06db3c7147ac3fe2022-12-22T03:19:21ZengMDPI AGCrystals2073-43522018-03-018414210.3390/cryst8040142cryst8040142β”-(CNB-EDT-TTF)4BF4; Anion Disorder Effects in Bilayer Molecular MetalsSandra Rabaça0Sandrina Oliveira1Vasco Gama2Isabel C. Santos3Gonçalo Oliveira4Elsa B. Lopes5Enric Canadell6Manuel Almeida7C2TN, Centro de Ciências e Tecnologias Nucleares, Instituto Superior Técnico, Universidade de Lisboa, E.N. 10, P-2695-066 Bobadela LRS, PortugalC2TN, Centro de Ciências e Tecnologias Nucleares, Instituto Superior Técnico, Universidade de Lisboa, E.N. 10, P-2695-066 Bobadela LRS, PortugalC2TN, Centro de Ciências e Tecnologias Nucleares, Instituto Superior Técnico, Universidade de Lisboa, E.N. 10, P-2695-066 Bobadela LRS, PortugalC2TN, Centro de Ciências e Tecnologias Nucleares, Instituto Superior Técnico, Universidade de Lisboa, E.N. 10, P-2695-066 Bobadela LRS, PortugalC2TN, Centro de Ciências e Tecnologias Nucleares, Instituto Superior Técnico, Universidade de Lisboa, E.N. 10, P-2695-066 Bobadela LRS, PortugalC2TN, Centro de Ciências e Tecnologias Nucleares, Instituto Superior Técnico, Universidade de Lisboa, E.N. 10, P-2695-066 Bobadela LRS, PortugalInstitut de Ciencia de Materials de Barcelona (ICMAB-CSIC), Campus UAB, E-08193 Bellaterra, SpainC2TN, Centro de Ciências e Tecnologias Nucleares, Instituto Superior Técnico, Universidade de Lisboa, E.N. 10, P-2695-066 Bobadela LRS, PortugalThe preparation and characterization of new salts based on the dissymmetrical TTF derivative CNB-EDT-TTF (cyanobenzene-ethylenedithio-tetrathiafulvalene) and BF4− anions, are reported. Depending on the electrocrystallization conditions salts with different stoichiometries, (CNB-EDT-TTF)BF4 and β”-(CNB-EDT-TTF)4BF4, can be obtained. The 1:1 salt is an electrical insulator isostructural to the ClO4 analogue previously described. The 4:1 salt is a new member of the family of 2D metals of this donor with different small anions X, (CNB-EDT-TTF)4X, characterized by a bilayer arrangement of the donors and it was obtained in a monoclinic polymorph with a β”-type donor packing pattern. The small anions in this compound are severely disordered between the donor bilayers, which present slightly larger lattice parameters than the isostructural ClO4 analogue. Both electrical conductivity and thermoelectric power measurements in single crystals denote metallic properties as predicted by electronic band structure calculations. As a consequence of the anion disorder the metallic regime of the electrical conductivity denotes electronic localization effects with a progressive increase of resistivity below ~25 K. Because of the larger lattice parameters the intermolecular interactions and electronic bandwidth are decreased compared to other (CNB-EDT-TTF)4X salts. The large and positive thermoelectric power S of this compound (~110 μV/K in the range 100–330 K) and its electrical conductivity σ = 20 S/cm at room temperature lead to a power factor S2σ = 24 μW/K2m, quite large among molecular conductors, placing these compounds as potential candidates for thermoelectric materials.http://www.mdpi.com/2073-4352/8/4/142molecular conductorsbilayer metalsradical cation saltsCNB-EDT-TTFthermoelectrics |
| spellingShingle | Sandra Rabaça Sandrina Oliveira Vasco Gama Isabel C. Santos Gonçalo Oliveira Elsa B. Lopes Enric Canadell Manuel Almeida β”-(CNB-EDT-TTF)4BF4; Anion Disorder Effects in Bilayer Molecular Metals Crystals molecular conductors bilayer metals radical cation salts CNB-EDT-TTF thermoelectrics |
| title | β”-(CNB-EDT-TTF)4BF4; Anion Disorder Effects in Bilayer Molecular Metals |
| title_full | β”-(CNB-EDT-TTF)4BF4; Anion Disorder Effects in Bilayer Molecular Metals |
| title_fullStr | β”-(CNB-EDT-TTF)4BF4; Anion Disorder Effects in Bilayer Molecular Metals |
| title_full_unstemmed | β”-(CNB-EDT-TTF)4BF4; Anion Disorder Effects in Bilayer Molecular Metals |
| title_short | β”-(CNB-EDT-TTF)4BF4; Anion Disorder Effects in Bilayer Molecular Metals |
| title_sort | β cnb edt ttf 4bf4 anion disorder effects in bilayer molecular metals |
| topic | molecular conductors bilayer metals radical cation salts CNB-EDT-TTF thermoelectrics |
| url | http://www.mdpi.com/2073-4352/8/4/142 |
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