Crystal structure and properties of l-tryptophanium hydrogen selenite

• Author(s): Paixão, José António ; Silva, Manuela Ramos ; Beja, Ana Matos ; Eusébio, Ermelinda
• Date: 2006
• Persistent ID: http://hdl.handle.net/10316/4402
• Origin: Estudo Geral - Universidade de Coimbra
• Subject(s): Phase transition; Hydrogen bonds; DSC measurements; Optical properties
• Document Type: Article
• Language: English

Description

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. http://www.sciencedirect.com/science/article/B6TH8-4JCBPGR-2/1/c662b0efb725c1398debc306ae4eb8f9