A survey of supramolecular association involving the oxide-O atom in the crystals of triorganoamine N-oxide derivatives, RR′R″N(+)O(−)

Trimethylamine N-oxide, Me3N(+)O(−), is an important molecule in biology and medicine. Herein, a survey of the interactions involving the oxide-O atom in crystals containing derivatives of Me3N(+)O(−), namely RR′R″N(+)O(−), is presented; R,R′, R″ = alkyl and/or aryl. A total of 119 RR′R″N(+)O(−) molecules were analysed for the supramolecular interactions involving the oxide-O atom. Hydrates form the largest class of crystals, comprising over 40 % of the 91 crystals investigated, a value slightly higher than expectation. Over 80 % of molecules had at least one O–H⋯O(−)(oxide) hydrogen bond: 3, 45 and 33 % of all molecules had three, two or one O–H⋯O(−)(oxide) hydrogen bonds, respectively. Further, nearly 15 % of molecules formed at least one N–H⋯O(−)(oxide) hydrogen bond, sometimes operating in concert with O–H⋯O(−)(oxide) hydrogen bonds. The overwhelming majority of molecules featured inter- and/or intra-molecular supporting C–H⋯O(−)(oxide) contacts so that a diverse range of supramolecular interaction patterns is apparent, a situation made more complicated by the appearance of different supramolecular association patterns often observed for independent molecules in crystals with more than one molecule in the crystallographic asymmetric-unit. Of the 6 % of molecules devoid of conventional A–H⋯O(−)(oxide) hydrogen bonds, all formed three or four inter-/intra-molecular C–H⋯O(−)(oxide) contacts usually characterised by at least one short H⋯O(−)(oxide) distance.