1,721,024 research outputs found
Mixed-vs-Segregated Stack Polymorphism in the N,N,N',N'-Tetramethylbenzidine-TCNQF4 Charge Transfer Complex
No full textOrganic charge transfer (CT) cocrystals are a wide class of 1-D materials based on stacks of planar π-electron donor (D) and acceptor (A) molecules overlapping their frontier orbitals due to the CT interaction. Most CT crystals have either a segregated or mixed stack motif: in segregated stacks, D and A molecules form separate columns, while in mixed stacks, D and A alternate along the same stack. Although CT crystals often display polymorphism, very few D-A pairs are known to crystallize with both stack motifs. Here, we present a new CT complex presenting both mixed and segregated stack phases, based on the strong donor N,N,N′,N′-Tetramethylbenzidine (N-TMB) and the strong acceptor TCNQF4. The combination of polarized IR and Raman spectroscopy with X-ray diffraction on single crystals found common structural and optical features between the two phases. The low temperature data also suggest that a stack distortion occurs in the segregated stack phase
Charge-sensitive vibrations in p-Chloranil: The strange case of the C=C antisymmetric stretching
No full textSpectroscopic characterization of (BEDT-TTF)<SUB>2</SUB>[Pt(S<SUB>2</SUB>C<SUB>4</SUB>O<SUB>2</SUB>)<SUB>2</SUB>] Charge Density Wave ground state
No full textTemperature-induced valence and structural instability in DMTTF-CA: Single-crystal Raman and infrared measurements
No full textA new type of neutral-ionic interface in mixed stack organic charge transfer crystals: Temperature induced ionicity change in ClMePD-DMeDCNQI
No full textComprehensive Optical Investigations of Charge Order in Organic Chain Compounds (TMTTF)2X
No full textCharge ordering in the (TMTTF)2X salts with centrosymmetric anions (X = PF‾6 , AsF‾6 , SbF‾6 ) leads to a ferroelectric state around 100 K. For the first time and in great completeness, the intra- and intermolecular vibrational modes of (TMTTF)2X have been investigated by infrared and Raman spectroscopy as a function of temperature and pressure for different polarizations. In this original paper, we explore the development and amount of charge disproportionation and the coupling of the electronic degrees of freedom to the counterions and the underlying lattice. The methyl groups undergo changes with temperature that are crucial for the anion cage formed by them. We find that the coupling of the TMTTF molecules to the hexafluorine anions changes upon cooling and especially at the charge-order transition, indicating a distortion of the anion. Additional features are identified that are caused by the anharmonic potential. The spin-Peierls transition entails additional modifications in the charge distribution. To complete the discussion, we also add the vibrational frequencies and eigenvectors based on ab-initio quantum-chemical calculations
Temperature and pressure studies of the continuous neutral-ionic borderline in ClMePD-DMeDCNQI
No full textNeutral to ionic pressure-induced phase transition in the mixed stack charge-transfer crystal ClMePD-DMeDCNQI
No full textExperimental determination of BEDT-TTF+ electron-molecular vibration constants through optical microreflectance
No full textPHYS. REV.
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