Pre-organization of 2,2′-diaminodiethylether, 2,2′-(ethylenedioxy)diethylamine and 1,4-diaminobutane in the solid state

Abstract

X-ray diffraction analysis of 10 crystal structures of co-crystals of acyclic diamines (with or without ether functions) and several dicarboxylic acids (maleic, fumaric, succinic and adipic) shows preferred types of intermolecular interactions. These include the formation by a doubly protonated amine molecule of a pattern of six, strong intermolecular hydrogen bonds with carboxy groups from acid molecules surrounding the amine. The folded conformation of the amine molecule is preferred for 2,2′-diaminodiethylether ( 1) and 2,2′-(ethylenedioxy)diethylamine ( 2). For 1,4-diaminobutane ( 3), the folded conformation was only found in the co-crystal with two molecules of adipic acid.