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Abstract: This contribution addresses standing questions about the nature and consequences of the ion self-assembly and magnetic structures, as well as the molecular motion of the crystalline structure as a function of the temperature, in halometalate materials based on imidazolium cation. We present the magnetic structure and magnetostructural correlations of 1-ethyl-2,3-dimethylimidazolium tetrachloridoferrate, (Edimim)[FeCl4], resolved by neutron diffraction studies. Single-crystal, synchrotron powder X-ray diffraction and powder neutron diffraction techniques have been combined to follow the temperature evolution on its crystallographic structure from 2 K close to its melting point (340 K). In this sense, slightly above room temperature (307 K) (Edimim)[FeCl4] presents a single-crystal to single-crystal transition (SCSC), from phase I (space group P21/n) to phase II (P21/m), accompanied by a notable increase in the disorder of the imidazolium cation, as well as in the metal complex anion. The temperature evolution and solid-phase transitions of the presented compound were followed in detail by synchrotron X-ray powder diffraction (SXPD), which confirms the occurrence of another phase transition at 330 K, phase III (P21/m), the crystal structure of which was elucidated from the SXPD pattern. Moreover, this material presents an anisotropic thermal expansion with a switch from axial positive to negative thermal expansion coefficients as the temperature is raised above the first phase transition, which has been correlated with the molecular motion of the imidazolium-based molecules, producing not only a shortening of the counterion···counterion distances but also the occurrence of different quasi-isoenergetic crystal structures as a function of the temperature.
Fuente: Inorganic Chemistry 2018 57 (4), 1787-1795
Editorial: American Chemical Society
Fecha de publicación: 02/02/2018
Nº de páginas: 9
Tipo de publicación: Artículo de Revista
Proyecto español: MAT2014-55049-C2-R : MAT2016-75883-C2-1-P
Url de la publicación: https://doi.org/10.1021/acs.inorgchem.7b02632
PALMERINA GONZALEZ IZQUIERDO
JESUS MARIA RODRIGUEZ FERNANDEZ
FERNÁNDEZ DÍAZ, MARÍA TERESA
MANUEL DE PEDRO DEL VALLE