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.
Zeitschrift für Kristallographie – Crystalline Materials offers a place for researchers to present results of their crystallographic studies. The journal includes theoretical as well as experimental research. It publishes Original Papers, Letters and Review Articles in manifold areas of crystallography.