Phase transition sequences in tetramethylammonium tetrachlorometallates by X-ray diffraction and spectroscopic measurements

Acta Crystallographica Section B: Structural Science, Crystal Engineering and Materials

5 years ago

Phase transition sequences in tetramethylammonium tetrachlorometallates by X-ray diffraction and spectroscopic measurements

$Phase transition sequences in tetramethylammonium tetrachlorometallates by X-ray diffraction and spectroscopic measurements$

Fernando Rodríguez, José A. Barreda-Argüeso, Garry J McIntyre, Jack Binns, Rafael Valiente, Fernando Aguado, Simon Parsons, Jesús González

The phase transition sequences of two members of the tetramethylammonium tetrachlorometallate(III) family of hybrid organic–inorganic salts have been determined and structurally characterized as a function of temperature for the first time. Unusually, a reduction in point-group symmetry with increasing temperature until reaching a cubic prototype phase is observed. Two additional intermediate phases are observed for Fe3+. First-principles calculations and the presence of short Cl…Cl contacts for Ga3+ suggest the [GaCl4]− anion to be conformationally hindered due to stronger lone-pair–σ-hole interactions. The conformationally more flexible Fe3+ structures show sublattice melting with the onset of rotational disorder in the [NMe4]+ cations occurring 40 K below the corresponding onset of rotational disorder in the [FeCl4]− sublattice.Structures and phase sequences for two tetramethylammonium tetrachlorometallate compounds have been determined as a function of temperature. Crystal-packing analysis and first-principles calculations were used to rationalize the experimentally determined sequence.

Publisher URL: http://onlinelibrary.wiley.com/resolve/doi

DOI: 10.1107/S2052520617006412