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  • 1
    Electronic Resource
    Electronic Resource
    Electronic and structural characterization of a charge transfer crystal with strong electronic correlations through infrared and Raman spectroscopy: TMPD–TCNQF4 (1988)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 89 (1988), S. 2704-2711 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The electronic and structural characterization of the title charge transfer (CI) complex is carried out mainly by the exploitation of the infrared powder spectrum and its temperature dependence from room temperature to 15 K as well as of the Raman powder spectrum at 15 K. The infrared spectrum shows that the complex has a fully ionic electronic ground state (ρ(approximately-equal-to)1) and the analysis of the spectroscopic effects due to the radical electron–intramolecular vibration interactions reveals a structure built up of segregated stacks of TMPD and TCNQF4. Moreover, this analysis shows that the TCNQF4 stacks are nonregular in the whole studied temperature range, whereas, by lowering temperature, the TMPD stacks undergo a phase transition from a regular to a nonregular structure with onset at about 180 K. The effective on-site electronic correlation parameter, the hopping integral, and the magnetic gap of both stacks in the nonregular phase are estimated by adopting a cluster model made up of a dimeric unit to describe the stacks and by comparison with known materials. On the same basis, the temperature dependence of the hopping integrals is also estimated. The collected information, considered in the light of the Peierls–Hubbard model, suggests that TMPD–TCNQF4 can be considered a compound with strong electronic correlations.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.455022
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  • 2
    Electronic Resource
    Electronic Resource
    Ionicity and electron molecular vibration interaction in mixed stack CT systems: M2P–TCNQ and M2P–TCNQF4 (1985)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 83 (1985), S. 3134-3145 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The powder Raman spectra and the polarized infrared absorption spectra of a polycrystalline oriented film of (1:1) CT complex of 5,10-dihydro-5,10-dimethylphenazine (M2P) with 7,7,8,8-tetracyanoquinodimethane (TCNQ) are reported together with the polarized reflectance infrared spectra of a mosaic of single crystals [(010) crystal face] and the conductivity spectra obtained from a Kramers–Krönig analysis of the reflectance data. The powder Raman and infrared spectra of M2P–TCNQF4 and their temperature dependence (300–15 K) are also presented. The M2P–TCNQ structure is known to be made up of donor–acceptor dimerized mixed stacks. The spectral features related to electron–molecular vibration (e–mv) interaction are successfully interpreted in terms of the dimer model, whose applicability is further validated after its first use in the case of the low temperature phase of tetrathiafulvalene–chloranil complex. The success is testified by the goodfit obtained between experimental and calculated vibronic features of the near and midinfrared spectra. The extracted values of the e–mv coupling constants of TCNQ moiety compare well with those obtained from other TCNQ complexes, whereas those of M2P are a first informative evaluation. The value of the degree of ionicity of M2P–TCNQ ( ρ=0.5±0.1) is obtained by completing the assignment of the spectra in terms of fundamental vibrational modes normally active under the molecular symmetry of the component molecules and by using carefully chosen diagnostic infrared frequencies. Results show that M2P–TCNQ is definitely one of the still rare cases of mixed stack CT complexes with intermediate ionicity. By using analogous criteria, the interpretation of room temperature and low temperature (15 K) spectra of M2P–TCNQF4 leads to the conclusion that for this complex ρ∼1.0. Its temperature dependent phase transition (T=120 K) between the room temperature regular mixed stack and the low temperature dimerized one is well characterized. The vibronic features appearing in the low-temperature infrared spectrum agree with predictions by the dimer model for a distorted stack. Consequently, it is likely that the phase transition is attributable to a dimerization of the stack due to a Spin–Peierls instability, in agreement with the previous indication given by magnetic susceptibility measurements.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.449829
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  • 3
    Electronic Resource
    Electronic Resource
    Charge–transfer organic crystals: Molecular vibrations and spectroscopic effects of electron–molecular vibration coupling of the strong electron acceptor TCNQF4 (1986)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 84 (1986), S. 4149-4162 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: A fundamental aspect in the study of the charge–transfer (CT) organic crystals with ionic or partially ionic ground states is the investigation of the spectroscopic effect of the electron–molecular vibration coupling. 7,7,8,8-tetracyano-2,3,5,6-tetrafluoroquinodimethane (TCNQF4), an electron acceptor much stronger than TCNQ, is an outstanding component of many interesting CT systems. A thorough vibrational analysis of the title compound and of its monomeric radical anion is reported. The analysis is based on the Raman depolarization ratio measurements and on infrared data of solutions of both neutral and ionic species as well as on polarized infrared spectra of oriented crystals of the neutral molecule. The vibrational assignment, completed by a normal coordinate analysis (NCA), brings to the identification of the ionization frequency shifts and to the choice of the fundamentals (b1uν19 and b2uν33) whose frequencies are diagnostic of the degree of charge transfer for a TCNQF4 moiety partner of a CT system. Through a combined use of a RHF-CNDO/S(CT) electronic calculation and of the eigenvectors of the radical anion given by the NCA, the numerical evaluation of the linear e–mv coupling constants is carried out. The relative values of these constants are extracted, by applying the dimer model, from the vibronic features of the infrared spectrum of the low temperature phase of Rb–TCNQF4. This compound is recognized, by comparison with the alkali salts of TCNQ, to display a phase transition at T(approximately-equal-to)130 K from a regular to a dimerized stack structure. From the analysis of all these data it is possible to characterize the spectroscopic vibronic effects related to e–mv coupling in CT systems of TCNQF4. This is successfully verified by the segregated dimerized stack system of DBTTF–TCNQF4 and applied to the not yet characterized system TSF–TCNQF4 which is recognized here as a fully ionic complex with segregated dimerized stack motif. As a consequence, through the vibrational spectra, TCNQF4 can be fruitfully used as a sensitive probe for structural and electronic characterization of its CT complexes.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.450086
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  • 4
    Electronic Resource
    Electronic Resource
    Optical Limiting Devices Based on C60 Derivatives in Sol-Gel Hybrid Organic-Inorganic Materials (2000)
    Springer
    Journal of sol gel science and technology 19 (2000), S. 263-266 
    Details
    ISSN: 1573-4846
    Keywords: hybrid materials ; 3-glycidoxypropyltrimethoxysilane ; fullerene derivatives ; optical limiting
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract A guest-host solid state device based on hybrid organic-inorganic materials and fullerene derivatives has been fabricated for optical limiting applications. Different 3-glycidoxypropyltrimethoxysilane derived hybrid matrices have been synthesized to increase the optical limiting performances. These matrices have shown high laser damage fluences, low light scattering, good transmittance in the visible range and allowed to deposit 10–100 μm thick films per single layer. The C60 derivatives have been functionalized with Si tri-alkoxide terminal groups and have reached a final concentration in the solid matrix up to 2 × 10−2 M·l−1. A multilayer system with a bottleneck structure has been developed to optimize a laser protection device.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1008704825802
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  • 5
    Electronic Resource
    Electronic Resource
    C60 derivatives embedded in sol-gel silica filmsThe authors wish to thank Ms. M. Zanetti for technical assistance. Thanks are also due to Dr. R. Seraglia for MALDI-MS data. This work was in part developed within the Progetto Finalizzato Materiali Speciali per Tecnologie Avanzate and the Progetto Strategico Materiali Innovativi of the C. N. R. (1995)
    Weinheim : Wiley-Blackwell
    Advanced Materials 7 (1995), S. 404-406 
    Details
    ISSN: 0935-9648
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/adma.19950070414
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