Crystal structure and properties of l-tryptophanium hydrogen selenite

Abstract

l-Tryptophanium hydrogen selenite was synthesised and structurally characterised at room and low temperature. The aminoacid is positively charged with the amine and carboxylic group protonated. It adopts a staggered conformation with the N1 gauche to C4 that is gauche to C1. The anion displays a pyramidal conformation with three different Se-O bond lengths, one characteristic of a double bond, another of a single bond and the third with an intermediate character. At room temperature there is a disordered hydrogen atom between the carboxylic group of the cation and the O atom of the anion with the intermediate Se-O bond length. At low temperature this hydrogen atom orders and attaches to the carboxylic group. This ordering is most likely related to the transition seen in DSC measurements occurring at -82.5 °C.