Solvates of Zwitterionic Rifampicin: Recurring Packing Motifs via Nonspecific Interactions

Abstract

Antibiotic rifampicin was recrystallized from solutions containing aliphatic alcohols, ketones or DMSO. Thirteen new solvates were obtained that were studied by X-ray crystallography. In these solvates rifampicin exists in a zwitterionic form. The reported solvates are classified into eight different structural types. Whereas rifampicin molecules in the solvates form diverse assemblies via hydrogen bonds, the recurring structural motif in these crystals is generated by nonspecific intermolecular interactions. This motif has the form of a periodic 1D rod and similar 1D motifs were found in the structures of other zwitterionic or ionic rifamycins. In rifampicin solvates, these rods form a basis for the construction of two types of 2D periodic modules: monolayers found in six structural types of rifampicin solvates and bilayers observed in two types of solvates. Diverse mutual arrangements of these 2D modules lead to the formation of channels with accommodated solvent molecules that consist 10-40% of the cry...