C60 Solvate with (1,1,2)-Trichloroethane: Dynamic Statistical Disorder and Mixed Conformation

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• 作者：Efstratia Mitsari ; Michela Romanini ; Navid Qureshi ; Josep Lluís Tamarit ; Maria Barrio ; Roberto Macovez
• 刊名：Journal of Physical Chemistry C
• 出版年：2016
• 出版时间：June 16, 2016
• 年：2016
• 卷：120
• 期：23
• 页码：12831-12839
• 全文大小：459K
• 年卷期：0
• ISSN：1932-7455

文摘

We present a full characterization of the orientationally disordered cocrystal of C<sub>60sub> with (1,1,2)-trichloroethane (C<sub>2sub>H<sub>3sub>Cl<sub>3sub>), by means of X-ray diffraction, Raman spectroscopy, and broadband dielectric spectroscopy. Our results include the determination of molecular conformations, lattice structure, positional disorder, and molecular reorientational dynamics down to the microsecond time scale. We find that, while in the disordered solid phase of pure C<sub>2sub>H<sub>3sub>Cl<sub>3sub> the molecules exist only in the gauche conformation, both gauche and transoid conformers are present in the solvate, where they occupy the largest interstitial cavities between the fullerene species. The two C<sub>2sub>H<sub>3sub>Cl<sub>3sub> conformers exhibit separate, independent relaxations, exhibiting simply activated behavior in the measured temperature range. The relaxation of the transoid conformer, which has twice the dipole moment of the gauche isomer, is significantly slower than that of the latter, due to the high polarizability of C<sub>60sub> resulting in an electrostatic drag against the reorientations of the dipolar C<sub>2sub>H<sub>3sub>Cl<sub>3sub> species. The observation of two distinct, simply activated relaxations freezing at distinct temperatures indicates that they are not truly many-body relaxations, which may be rationalized considering that the C<sub>2sub>H<sub>3sub>Cl<sub>3sub> molecules are separated by the relatively bulky C<sub>60sub> spacers.