title: Crystal structures and hydrogen bonding in the anhydrous tryptaminium salts of the isomeric (2,4-di-chloro-phen-oxy)acetic and (3,5-di-chloro-phen-oxy)acetic acids.
abstract: The anhydrous salts of 2-(1H-indol-3-yl)ethanamine (tryptamine) with isomeric (2,4-di-chloro-phen-oxy)acetic acid (2,4-D) and (3,5-di-chloro-phen-oxy)acetic (3,5-D), both C10H13N2 (+)·C8H5Cl2O3 (-) [(I) and (II), respectively], have been determined and their one-dimensional hydrogen-bonded polymeric structures are described. In the crystal of (I), the aminium H atoms are involved in three separate inter-species N-H⋯O hydrogen-bonding inter-actions, two with carboxyl-ate O-atom acceptors and the third in an asymmetric three-centre bidentate carboxyl-ate O,O' chelate [graph set R 1 (2)(4)]. The indole H atom forms an N-H⋯Ocarboxyl-ate hydrogen bond, extending the chain structure along the b-axis direction. In (II), two of the three aminium H atoms are also involved in N-H⋯Ocarboxyl-ate hydrogen bonds similar to (I) but with the third, a three-centre asymmetric inter-action with carboxyl-ate and phen-oxy O atoms is found [graph set R 1 (2)(5)]. The chain polymeric extension is also along b. There are no π-π ring inter-actions in either of the structures. The aminium side-chain conformations differ significantly between the two structures, reflecting the conformational ambivalence of the tryptaminium cation, as found also in the benzoate salts.
authors.affiliation: Science and Engineering Faculty, Queensland University of Technology, GPO Box 2434, Brisbane, Queensland 4001, Australia.
authors.forename: Graham
authors.initials: G
authors.lastname: Smith
authors.affiliation: Exilica Ltd., The Technocentre, Puma Way, Coventry CV1 2TT, England.
authors.forename: Daniel E
authors.initials: DE
authors.lastname: Lynch
keywords: 2,4-D; 3,5-D; crystal structure; herbicides; hydrogen bonding; phen­oxy­acetic acids; tryptamine salts