Symmetry breaking and structural changes at the neutral-to-ionic transition in tetrathiafulvalene-<i>p</i>-chloranil

Cointe, M. Le; Lemée-Cailleau, Marie–Hélène; Cailleau, H.; Toudic, Bertrand; Toupet, Loı̈c; Heger, G.; Moussa, F.; Schweiß, P.; Kraft, K.-H.; Karl, N.

doi:10.1103/physrevb.51.3374

Cited by 213 publications

(267 citation statements)

References 40 publications

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“…the one of the I phase). No trace of this reflection was detected at -2 ns, time at which the data refinement reveals N phase strictly identical to the one at thermal equilibrium (Le Cointe et al, 1995).…”

Section: Cooperative Effects Around Neutral-ionic Phase Transitionmentioning

confidence: 98%

“…. At thermal equilibrium, this compound undergoes the so-called Neutral-Ionic (N--I) phase transition at 81 K. It couples changes of molecular electronic states (Jacobsen et al, 1983) with intra-and intermolecular rearrangements (symmetry-breaking, Le Cointe et al, 1995). The symmetry breaking and the ferroelectric order in the low temperature I phase is detected through the onset of 0k0 : k ¼ 2n þ 1 Bragg reflections (space group Pn, whereas in the high temperature N phase the group is P2 1 /n).…”

Section: Cooperative Effects Around Neutral-ionic Phase Transitionmentioning

confidence: 99%

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State of the art and opportunities in probing photoinduced phase transitions in molecular materials by conventional and picosecond X-ray diffraction

Collet¹,

Cointe²,

Lorenc³

et al. 2008

Zeitschrift Für Kristallographie - Crystalline Materials

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Abstract. The optical control of the macroscopic physical properties (magnetic, optical . . .) of a material by laser irradiation is gaining interest through the emerging field of photoinduced phase transitions. Light-induced changes of the macroscopic state of a material involves subtle coupling between the electronic and structural degrees of freedom, which are essential to stabilize the photo-excited state, different in nature from the stable state. Therefore the new experimental field of photocrystallography plays a key role. It goes far beyond simple structural analysis under laser excitation. By playing on different physical parameters and developing the techniques and analysis, one can investigate new out of equilibrium physics through light-driven cooperative dynamics and transformations in materials. This paper is reviewing different aspects of the use of photocrystallography to investigate the nature, the mechanisms and the dynamics of photoinduced phase transitions for photo-steady or long-lived states, as well as transformations driven by an ultra-short light pulse. We also give a brief overview on recent advances in time-resolved crystallography with 100 ps resolution.

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Section: Cooperative Effects Around Neutral-ionic Phase Transitionmentioning

confidence: 98%

Section: Cooperative Effects Around Neutral-ionic Phase Transitionmentioning

confidence: 99%

State of the art and opportunities in probing photoinduced phase transitions in molecular materials by conventional and picosecond X-ray diffraction

Collet¹,

Cointe²,

Lorenc³

et al. 2008

Zeitschrift Für Kristallographie - Crystalline Materials

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“…Hence, charge transfer takes place between them. Both the TTF and CA molecules are arranged parallel to their molecular plane in the unit cell with a distance of 3.70 Å [2]. Thereby, they are shifted and rotated slightly towards each other, leading to a maximum overlap of the molecular orbitals.…”

Section: Introductionmentioning

confidence: 99%

“…Thereby, they are shifted and rotated slightly towards each other, leading to a maximum overlap of the molecular orbitals. First studies on the crystal structure and the bond lengths of the C=C double bond of TTF and CA as well as the C=O bonds in CA reveal that the molecules are almost neutral at room temperature caused by a small charge transfer between TTF and CA [3] that can be attributed to the large intermolecular distance of 3.70 Å [2]. Indeed, infrared measurements show that the charge transfer is ρ = 0.2 e [4,5] at ambient conditions.…”

Section: Introductionmentioning

confidence: 99%

Infrared Investigations of the Neutral-Ionic Phase Transition in TTF-CA and Its Dynamics

Dressel

Peterseim

2017

Crystals

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Abstract:The neutral-ionic phase transition in TTF-CA was investigated by steady-state and time-resolved infrared spectroscopy. We describe the growth of high-quality single crystals and their characterization. Extended theoretical calculations were performed in order to obtain the band structure, the molecular vibrational modes and the optical spectra along all crystallographic axes. The theoretical results are compared to polarization-dependent infrared reflection experiments. The temperature-dependent optical conductivity is discussed in detail. We study the photo-induced phase transition in the vicinity of thermally-induced neutral-ionic transition. The observed temporal dynamics of the photo-induced states is attributed to the random-walk of neutral-ionic domain walls. We simulate the random-walk annihilation process of domain walls on a one-dimensional chain.

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“…During the last fifty years perhalogenosemiquinones were studied by various techniques: EPR, 4-6 UV/Vis 7 and IR/Raman spectroscopy [8][9][10][11] and computational methods. [12][13][14][15] Several charge-transfer systems involving tetrachloro-1,4-benzoquinone (Cl4Q) [16][17][18][19][20] and tetrabromo-1,4-benzoquinone (Br4Q), 21,22 where radical anions can be stabilised under appropriate conditions, have also been designed. A crystallographic study of tetrachlorosemiquinone radical anion-in its well-known potassium salt3-was attempted in a Rudjer Bo_skovi_c Institute, Bijeni_cka 54, HR-10000 Zagreb, Croatia.…”

mentioning

confidence: 99%

Stabilisation of tetrabromo- and tetrachlorosemiquinone (bromanil and chloranil) anion radicals in crystals

et al. 2011

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Crystal structures of alkali salts of tetrahaolgenosemiquinone anion radical acetone solvates and their solvent-free salts are determined. p-Semiquinone anion radical reveals enhanced aromaticity of the ring compared to the quinone. A pair of p-stacked radical anion (psemiquinone) rings occurs in crystal structures of potassium and rubidium salts of tetrachlorosemiquinone anion acetone solvates and their potassium tetrabromo analogue. The ring centroid separation distances are about 3.2 Å and carbon-carbon contacts between the contiguous rings are 0.3 Å shorter than the sum of van der Waals radii. The spin-coupling of the two unpaired electrons between the two anion radical rings (forming a stacked dimer) correlates with the diamagnetic property of the crystals. Magnetic properties of alkali salts of tetrahaolgenosemiquinone anion radical acetone solvates were examined by electron paramagnetic resonance spectroscopy. IntroductionQuinones and semiquinone radicals undergo easily reversible oxidation-reduction reactions and they are excellent electron carriers. Due to influence of the functional groups, quinones may have various values of the standard redox potential. The oxidation potential of the quinones with electron-donating groups such as -OH, is lower, and with electronwithdrawing groups such as -Cl and -NO2, the potential becomes higher. These unique electron properties of quinones are exploited for syntheses, both, in laboratory and by nature in vivo. 1,2 Substituents on the quinoid ring modify electron density affecting oxidation potential and stability of the semiquinone radical (Scheme 1). Perhalogenated benzoquinones are easily reduced and their radicals are rather stable; four electronegative substituents make electron density in the ring significantly lower. Sodium and potassium salts of tetrachlorosemiquinone anion radical were first prepared in 1912 by Torrey and Hunter 3 by reaction of alkali iodide and tetrachloroquinone in acetone. Green salts with formulae NaC 6 C l4 O 2 and KC 6 C l4 O 2 precipitated from cold acetone but quickly decomposed upon heating. During the last fifty years perhalogenosemiquinones were studied by various techniques: EPR, 4-6 UV/Vis 7 and IR/Raman spectroscopy [8][9][10][11] and computational methods. [12][13][14][15] Several charge-transfer systems involving tetrachloro-1,4-benzoquinone (Cl4Q) [16][17][18][19][20] and tetrabromo-1,4-benzoquinone (Br4Q), 21,22 where radical anions can be stabilised under appropriate conditions, have also been designed. A crystallographic study of tetrachlorosemiquinone radical anion-in its well-known potassium salt3-was attempted in a Rudjer Bo_skovi_c Institute, Bijeni_cka 54, HR-10000 Zagreb, Croatia. E-mail: kmolcano@irb.hr Molčanov, K., , "Stabilisation of tetrabromo-and tetrachlorosemiquinone (bromanil and chloranil) anion radicals in crystals", CrystEngComm, Vol.13, No.16, 1973 23 using a film method (Weissenberg camera). However, due to an extremely weak diffraction of poor crystals the authors could only determine unit cells of...

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Symmetry breaking and structural changes at the neutral-to-ionic transition in tetrathiafulvalene-p-chloranil

Cited by 213 publications

References 40 publications

State of the art and opportunities in probing photoinduced phase transitions in molecular materials by conventional and picosecond X-ray diffraction

State of the art and opportunities in probing photoinduced phase transitions in molecular materials by conventional and picosecond X-ray diffraction

Infrared Investigations of the Neutral-Ionic Phase Transition in TTF-CA and Its Dynamics

Stabilisation of tetrabromo- and tetrachlorosemiquinone (bromanil and chloranil) anion radicals in crystals

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