First crystal structure of a Pigment Red 52 compound: DMSO solvate hydrate of the monosodium salt.

Pigment Red 52, Na2[C18H11ClN2O6S], is an industrially produced hydrazone-laked pigment. It serves as an inter-mediate in the synthesis of the corresponding Ca2+ and Mn2+ salts, which are used commercially for printing inks and lacquers. Hitherto, no crystal structure of any salt of Pigment Red 52 is known. Now, single crystals have been obtained of a dimethyl sulfoxide solvate hydrate of the monosodium salt of Pigment Red 52, namely, monosodium 2-[2-(3-carb-oxy-2-oxo-1,2-di-hydro-naphthalen-1-yl-idene)hydrazin-1-yl]-5-chloro-4-methyl-benz-ene-sulfonate dimethyl sulfoxide monosolvate monohydrate, Na+·C18H12ClN2O6S-·H2O·C2H6OS, obtained from in-house synthesized Pigment Red 52. The crystal structure was determined by single-crystal X-ray diffraction at 173 K. In this monosodium salt, the SO3 - group is deprotonated, whereas the COOH group is protonated. The residues form chains via ionic inter-actions and hydrogen bonds. The chains are arranged in polar/non-polar double layers. © Tapmeyer et al. 2021.