Polymorphism and solid solutions of trimethylammonium monocarboranes

Jakob Grinderslev, Lasse Najbjerg Skov, Daniel Risskov Sørensen, Innokenty Kantor, Mads Ry Vogel Jørgensen, Torben René Jensen*

*Corresponding author for this work

Research output: Contribution to journal/Conference contribution in journal/Contribution to newspaperJournal articleResearchpeer-review


Metal closo-boranes have recently received significant attention as solid-state electrolytes due to their high thermal and electrochemical stability, and the weak interaction between the cat- and anion, facilitating fast ionic conductivity. Here we report a synthesis method for obtaining a novel mixed closo-carborane compound, [NH(CH 3) 3][(CB 8H 9) 0.26(CB 9H 10) 0.66(CB 11H 12) 0.08]. The crystal structures are investigated for [NH(CH 3) 3][CB 9H 10] and [NH(CH 3) 3][(CB 8H 9) 0.26(CB 9H 10) 0.66(CB 11H 12) 0.08], revealing that the latter forms a solid solution isostructural to [NH(CH 3) 3][CB 9H 10]. The compounds exhibit polymorphism as a function of temperature, and we report the discovery of four polymorphs of [NH(CH 3) 3][CB 9H 10] and four isostructural solid solution [NH(CH 3) 3][(CB 8H 9) 0.26(CB 9H 10) 0.66(CB 11H 12) 0.08], along with a high-temperature decomposition intermediate of the latter. The α-polymorph is an ordered structure, with increasing amounts of disorder for the β- and γ-polymorphs, while the high temperature δ- and ϵ-polymorphs at T > 476 K are fully disordered on both the cation and anion site. These new compounds may be used as precursors for new types of solid-state ionic conductors.

Original languageEnglish
JournalDalton Transactions
Pages (from-to)15806-15815
Number of pages10
Publication statusPublished - Sept 2022


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