A zwitterion of 1,5-bis(2-hydroxybenzamido)-3-azapentane: a two-dimensional hydrogen-bonding network involving dimers.

The title compound, 2-{N-[2-(2-hydroxybenzamido)ethylammonioethyl]aminocarbonyl}phenolate, C18H21N3O4, crystallizes in a zwitterionic form as a result of intermolecular proton transfer and possesses a negatively charged phenolate group and a protonated amino group. The 2-hydroxybenzamide and 2-(aminocarbonyl)phenolate moieties attached to the two ends of the C-C-N-C-C backbone adopt a cis conformation in relation to this backbone. All N- and O-bound H atoms are involved in hydrogen-bond formation; the zwitterions are first linked into head-to-tail dimers, which are further organized into a two-dimensional network parallel to the crystallographic bc plane.