Factors influencing the formation of polybromide monoanions in solutions of ionic liquid bromide salts

Abstract

Six different bromide salts – tetraethylammonium bromide ([N_2,2,2,2]Br, 1Br), 1-ethyl-1-methylpiperidinium bromide ([C₂MPip]Br, 2Br), 1-ethyl-1-methylpyrrolidinium bromide ([C₂MPyrr]Br, 3Br), 1-ethyl-3-methylimidazolium bromide ([C₂MIm]Br, 4Br), 1-ethylpyridinium bromide ([C₂Py]Br, 5Br), and 1-(2-hydroxyethyl)pyridinium bromide ([C₂OHPy]Br, 6Br) – were studied in regards to their capacity to form polybromide monoanion products on addition of molecular bromine in acetonitrile solutions. Using complementary spectroscopic and computational methods for the examination of tribromide and pentabromide anion formation, key factors influencing polybromide sequestration were identified. Here, we present criteria for the targeted synthesis of highly efficient bromine sequestration agents.