Abstract
The X-ray structures of three new 1:1 pharmaceutical cocrystals of 11-azaartemisinin (11-Aza; systematic name: 1,5,9-trimethyl-14,15,16-trioxa-11-azatetracyclo[10.3.1.04,13.08,13]hexadecan-10-one, C15H23NO4) with bromo-substituted salicylic acids [namely, 5-bromo- (5-BrSalA, C7H5BrO3), 4-bromo- (4-BrSalA, C7H5BrO3) and 3,5-dibromosalicylic acid (3,5-Br2SalA, C7H4Br2O3)] are reported. All the structures are related to the parent 11-Aza:SalA cocrystal (monoclinic P21) reported previously. The 5-BrSalA analogue is isostructural with the parent, with lattice expansion along the c axis. The 4-BrSalA and 3,5-Br2SalA cocrystals retain the highly preserved 21 stacks of the molecular pairs, but these pack with a varying degree of slippage with respect to neighbouring stacks, altering the close contacts between them, and represent two potential alternative homostructural arrangements for the parent compound. Structure redeterminations of the bromosalicylic acids 5-BrSalA, 4-BrSalA and 3,5-Br2SalA at 100 K show that the packing efficiency of the cocrystals need not be higher than the parent coformers, based on specific-volume calculations, attributable to the strong O—H...O=C hydrogen bonds of 2.54 Å in the cocrystals.
Funder
Research Grants Council of Hong Kong
Hong Kong Branch of the Southern Marine Science and Engineering Guangdong Laboratory
Publisher
International Union of Crystallography (IUCr)
Subject
Materials Chemistry,Inorganic Chemistry,Physical and Theoretical Chemistry,Condensed Matter Physics