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Licensed Unlicensed Requires Authentication Published by Oldenbourg Wissenschaftsverlag August 4, 2010

X-ray powder diffraction, solid-state NMR and dispersion-corrected DFT calculations to investigate the solid state structure of 2-ammonio-5-chloro-4-methylbenzenesulfonate

Sandor L. Bekö, Silke D. Thoms, Jürgen Brüning, Edith Alig, Jacco van de Streek, Andrea Lakatos, Clemens Glaubitz and Martin U. Schmidt
From the journal


The title compound, also called CLT acid, is an industrial intermediate in the synthesis of laked red azo pigments for newspaper printing. Solid-state NMR and IR experiments revealed the compound to exist as the zwitterionic tautomer in the solid state.

The crystal structure was solved from X-ray powder diffraction data by means of real-space methods using the program DASH 3.1. Subsequently the structure was refined by the Rietveld method with TOPAS 4.1. The zwitterionic tautomer gave better confidence values than the non-zwitterionic tautomer. Finally the structure was confirmed by dispersion-corrected density-functional calculations.

The compound crystallises in the monoclinic space group Ia, Z = 4 with a = 5.49809(7) Å, b = 32.8051(5) Å, c = 4.92423(7) Å, β = 93.5011(7)° and V = 886.50(2) Å3. The molecules form a herringbone pattern with a double layer structure consisting of alternating polar and non-polar layers. Within the polar layers hydrogen bonds and ionic interactions are dominant, whereas the fragments in the non-polar layers are connected by van der Waals interactions.

* Correspondence address: Goethe University, Institute of Inorganic and Analytical Chemistry, Max-von-Laue-Str. 7, 60438 Frankfurt am Main, Deutschland,

Published Online: 2010-08-04
Published in Print: 2010-09

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