Mixed valence radical cations and intermolecular complexes derived from indenofluorene-extended tetrathiafulvalenes

Mikkel Andreas Christensen; Christian Richard Parker; Thomas Just Sørensen; Sebastian de Graaf; Thorbjørn Juul Morsing; Theis Brock-Nannestad; Jesper Bendix; Michael M. Haley; Peter Rapta; Andrey Danilov; Sergey Kubatkin; Ole Hammerich; Mogens Brøndsted Nielsen

doi:10.1039/c4tc02178a

Mixed valence radical cations and intermolecular complexes derived from indenofluorene-extended tetrathiafulvalenes

Mikkel Andreas Christensen, Christian Richard Parker, Thomas Just Sørensen, Sebastian de Graaf, Thorbjørn Juul Morsing, Theis Brock-Nannestad, Jesper Bendix, Michael M. Haley, Peter Rapta, Andrey Danilov, Sergey Kubatkin, Ole Hammerich, Mogens Brøndsted Nielsen

Department of Chemistry

33 Citations (Scopus)

Abstract

Engineering of mixed-valence (MV) radical cations and intermolecular complexes based on π-extended tetrathiafulvalenes (TTFs) is central for the development of organic conductors. On another front, redox-controlled dimerization of radical cations has recently been recognized as an important tool in supramolecular chemistry. Here we show that π-extended TTFs based on the indenofluorene core, prepared by Horner-Wadsworth-Emmons reactions, undergo reversible and stepwise one-electron oxidations and that the detectable, intermediate radical cation forms remarkably strong intermolecular MV ([neutral·cation]) and π-dimer ([cation·cation]) complexes with near-infrared radical cation absorptions. The radical cation itself seems to be a so-called Class III MV species in the Robin-Day classification. The formation of MV dimers was corroborated by ESR spectroelectrochemical studies, revealing two slightly different ESR signals upon oxidation, one assigned to the MV dimer and the other to the cation monomer. Crystals of the radical cation with different anions (PF₆^-, BF₄^-, and TaF₆^-) were grown by electrocrystallization. Conductance studies revealed that the salts behave as semiconductors with the hexafluorotantalate salt exhibiting the highest conductance. Using a custom-built ESR spectrometer with sub-femtomole sensitivity, the magnetic properties of one crystal were investigated. While the spin-to-spin interaction between radical cations was negligible, a high cooperativity coupling to the microwave field was observed - as a result of an exceptionally narrow spin line width and high spin density. This could have great potential for applications in quantum computation where crystalline spin ensembles are exploited for their long coherence times.

Original language	English
Journal	Journal of Materials Chemistry C
Volume	2
Issue number	48
Pages (from-to)	10428-10438
Number of pages	11
ISSN	2050-7526
DOIs	https://doi.org/10.1039/c4tc02178a
Publication status	Published - 28 Dec 2014

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Christensen, M. A., Parker, C. R., Sørensen, T. J., de Graaf, S., Morsing, T. J., Brock-Nannestad, T., Bendix, J., Haley, M. M., Rapta, P., Danilov, A., Kubatkin, S., Hammerich, O., & Nielsen, M. B. (2014). Mixed valence radical cations and intermolecular complexes derived from indenofluorene-extended tetrathiafulvalenes. Journal of Materials Chemistry C, 2(48), 10428-10438. https://doi.org/10.1039/c4tc02178a

Mixed valence radical cations and intermolecular complexes derived from indenofluorene-extended tetrathiafulvalenes. / Christensen, Mikkel Andreas; Parker, Christian Richard; Sørensen, Thomas Just et al.

In: Journal of Materials Chemistry C, Vol. 2, No. 48, 28.12.2014, p. 10428-10438.

Research output: Contribution to journal › Journal article › Research › peer-review

Christensen, MA, Parker, CR, Sørensen, TJ, de Graaf, S, Morsing, TJ, Brock-Nannestad, T , Bendix, J, Haley, MM, Rapta, P, Danilov, A, Kubatkin, S, Hammerich, O & Nielsen, MB 2014, 'Mixed valence radical cations and intermolecular complexes derived from indenofluorene-extended tetrathiafulvalenes', Journal of Materials Chemistry C, vol. 2, no. 48, pp. 10428-10438. https://doi.org/10.1039/c4tc02178a

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title = "Mixed valence radical cations and intermolecular complexes derived from indenofluorene-extended tetrathiafulvalenes",

abstract = "Engineering of mixed-valence (MV) radical cations and intermolecular complexes based on π-extended tetrathiafulvalenes (TTFs) is central for the development of organic conductors. On another front, redox-controlled dimerization of radical cations has recently been recognized as an important tool in supramolecular chemistry. Here we show that π-extended TTFs based on the indenofluorene core, prepared by Horner-Wadsworth-Emmons reactions, undergo reversible and stepwise one-electron oxidations and that the detectable, intermediate radical cation forms remarkably strong intermolecular MV ([neutral·cation]) and π-dimer ([cation·cation]) complexes with near-infrared radical cation absorptions. The radical cation itself seems to be a so-called Class III MV species in the Robin-Day classification. The formation of MV dimers was corroborated by ESR spectroelectrochemical studies, revealing two slightly different ESR signals upon oxidation, one assigned to the MV dimer and the other to the cation monomer. Crystals of the radical cation with different anions (PF6-, BF4-, and TaF6-) were grown by electrocrystallization. Conductance studies revealed that the salts behave as semiconductors with the hexafluorotantalate salt exhibiting the highest conductance. Using a custom-built ESR spectrometer with sub-femtomole sensitivity, the magnetic properties of one crystal were investigated. While the spin-to-spin interaction between radical cations was negligible, a high cooperativity coupling to the microwave field was observed - as a result of an exceptionally narrow spin line width and high spin density. This could have great potential for applications in quantum computation where crystalline spin ensembles are exploited for their long coherence times.",

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doi = "10.1039/c4tc02178a",

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T1 - Mixed valence radical cations and intermolecular complexes derived from indenofluorene-extended tetrathiafulvalenes

AU - Christensen, Mikkel Andreas

AU - Parker, Christian Richard

AU - Sørensen, Thomas Just

AU - de Graaf, Sebastian

AU - Morsing, Thorbjørn Juul

AU - Brock-Nannestad, Theis

AU - Bendix, Jesper

AU - Haley, Michael M.

AU - Rapta, Peter

AU - Danilov, Andrey

AU - Kubatkin, Sergey

AU - Hammerich, Ole

AU - Nielsen, Mogens Brøndsted

PY - 2014/12/28

Y1 - 2014/12/28

N2 - Engineering of mixed-valence (MV) radical cations and intermolecular complexes based on π-extended tetrathiafulvalenes (TTFs) is central for the development of organic conductors. On another front, redox-controlled dimerization of radical cations has recently been recognized as an important tool in supramolecular chemistry. Here we show that π-extended TTFs based on the indenofluorene core, prepared by Horner-Wadsworth-Emmons reactions, undergo reversible and stepwise one-electron oxidations and that the detectable, intermediate radical cation forms remarkably strong intermolecular MV ([neutral·cation]) and π-dimer ([cation·cation]) complexes with near-infrared radical cation absorptions. The radical cation itself seems to be a so-called Class III MV species in the Robin-Day classification. The formation of MV dimers was corroborated by ESR spectroelectrochemical studies, revealing two slightly different ESR signals upon oxidation, one assigned to the MV dimer and the other to the cation monomer. Crystals of the radical cation with different anions (PF6-, BF4-, and TaF6-) were grown by electrocrystallization. Conductance studies revealed that the salts behave as semiconductors with the hexafluorotantalate salt exhibiting the highest conductance. Using a custom-built ESR spectrometer with sub-femtomole sensitivity, the magnetic properties of one crystal were investigated. While the spin-to-spin interaction between radical cations was negligible, a high cooperativity coupling to the microwave field was observed - as a result of an exceptionally narrow spin line width and high spin density. This could have great potential for applications in quantum computation where crystalline spin ensembles are exploited for their long coherence times.

AB - Engineering of mixed-valence (MV) radical cations and intermolecular complexes based on π-extended tetrathiafulvalenes (TTFs) is central for the development of organic conductors. On another front, redox-controlled dimerization of radical cations has recently been recognized as an important tool in supramolecular chemistry. Here we show that π-extended TTFs based on the indenofluorene core, prepared by Horner-Wadsworth-Emmons reactions, undergo reversible and stepwise one-electron oxidations and that the detectable, intermediate radical cation forms remarkably strong intermolecular MV ([neutral·cation]) and π-dimer ([cation·cation]) complexes with near-infrared radical cation absorptions. The radical cation itself seems to be a so-called Class III MV species in the Robin-Day classification. The formation of MV dimers was corroborated by ESR spectroelectrochemical studies, revealing two slightly different ESR signals upon oxidation, one assigned to the MV dimer and the other to the cation monomer. Crystals of the radical cation with different anions (PF6-, BF4-, and TaF6-) were grown by electrocrystallization. Conductance studies revealed that the salts behave as semiconductors with the hexafluorotantalate salt exhibiting the highest conductance. Using a custom-built ESR spectrometer with sub-femtomole sensitivity, the magnetic properties of one crystal were investigated. While the spin-to-spin interaction between radical cations was negligible, a high cooperativity coupling to the microwave field was observed - as a result of an exceptionally narrow spin line width and high spin density. This could have great potential for applications in quantum computation where crystalline spin ensembles are exploited for their long coherence times.

U2 - 10.1039/c4tc02178a

DO - 10.1039/c4tc02178a

M3 - Journal article

SN - 2050-7526

VL - 2

SP - 10428

EP - 10438

JO - Journal of Materials Chemistry C

JF - Journal of Materials Chemistry C

IS - 48

ER -

Mixed valence radical cations and intermolecular complexes derived from indenofluorene-extended tetrathiafulvalenes

Abstract

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