Crystal polymorphism in 1-butyl-3-methylimidazolium halides: supporting ionic liquid formation by inhibition of crystallizationElectronic supplementary information (ESI) available: packing diagrams for I and II; table of closest contacts for I, I-Br and II. See http://www.rsc.org/suppdata/cc/b3/b304

Crystallization of 1-butyl-3-methylimidazolium chloride from mixed ionic liquid or ionic liquid–aromatic solution, and from the melt yields different crystalline polymorphs, the first direct evidence for inhibition of crystallization in ionic liquids by polymorphism.