Bulk and molecular compressibilities of organic-inorganic hybrids [(CH3)4N]2MnX4 (X = Cl, Br); Role of intermolecular interactions

Jose Antonio Barreda-Argüeso, Lucie Nataf, Yamilet Rodríguez-Lazcano, Fernando Aguado, Jesús González, Rafael Valiente, Fernando Rodríguez, Heribert Wilhelm, Andrew P. Jephcoat

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Abstract

This work reports an X-ray diffraction, X-ray absorption, and Raman spectroscopy study of [(CH3)4N]2MnX4 (X = Cl, Br) under pressure. We show that both compounds share a similar phase diagram with pressure. A P21/c monoclinic structure describes precisely the [(CH3)4N]2MnCl4 crystal in the 0.1-6 GPa range, prior to crystal decomposition and amorphization, while [(CH3)4N]2MnBr4 can be described by a Pmcn orthorhombic structure in its stability pressure range of 0-3 GPa. These materials are attractive systems for pressure studies since they are readily compressible through the weak interaction between organic/inorganic [(CH3)4N+/MnX42-] tetrahedra through hydrogen bonds and contrast with the small compressibility of both tetrahedra. Here we determine the equation-of-state (EOS) of each crystal and compare it with the corresponding local EOS of the MnX42- and (CH3)4N+ tetrahedra, the compressibility of which is an order and 2 orders of magnitude smaller than the crystal compressibility, respectively, in both chloride and bromide. The variations of the Mn-Cl bond distance obtained by extended X-ray absorption fine structure and the frequency of the totally symmetric ν1(A1) Raman mode of MnCl42- with pressure in [(CH3)4N]2MnCl4 allowed us to determine the associated Grüneisen parameter (γloc = 1.15) and hence an accurate local EOS. On the basis of a local compressibility model, we obtained the Grüneisen parameters and corresponding variations of the intramolecular Mn-Br and C-N bond distances of MnBr42-loc = 1.45) and (CH3)4N+loc = 3.0) in [(CH3)4N]2MnBr4.

Original languageEnglish
Pages (from-to)10708-10715
Number of pages8
JournalInorganic Chemistry
Volume53
Issue number19
DOIs
Publication statusPublished - Oct 6 2014

ASJC Scopus subject areas

  • Physical and Theoretical Chemistry
  • Inorganic Chemistry

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    Barreda-Argüeso, J. A., Nataf, L., Rodríguez-Lazcano, Y., Aguado, F., González, J., Valiente, R., Rodríguez, F., Wilhelm, H., & Jephcoat, A. P. (2014). Bulk and molecular compressibilities of organic-inorganic hybrids [(CH3)4N]2MnX4 (X = Cl, Br); Role of intermolecular interactions. Inorganic Chemistry, 53(19), 10708-10715. https://doi.org/10.1021/ic501854g