Crystal water as the mol­ecular glue for obtaining different co-crystal ratios: the case of gallic acid tris-caffeine hexa­hydrate

Acta Crystallographica Section E: Crystallographic Communications

Vella-Zarb, L.¹ 

[1] University of Malta, Msida, MSD 2080, Malta

关键词: CRYSTAL STRUCTURE;    ORGANIC CO-CRYSTAL;    HYDRATE;    GALLIC ACID;    CAFFEINE;   

DOI  :  10.1107/S2056989018004528

学科分类：数学（综合）

来源: International Union of Crystallography

【 摘 要 】

The crystal structure of the hexa­hydrate co-crystal of gallic acid and caffeine, C7H6O5·3C8H10N4O2·6H2O or GAL3CAF·6H2O, is a remarkable example of the importance of hydrate water acting as structural glue to facilitate the crystallization of two components of different stoichiometries and thus to compensate an imbalance of hydrogen-bond donors and acceptors. The water mol­ecules provide the additional hydrogen bonds required to form a crystalline solid. Whereas the majority of hydrogen bonds forming the inter­molecular network between gallic acid and caffeine are formed by crystal water, only one direct classical hydrogen bond between two mol­ecules is formed between the carb­oxy­lic oxygen of gallic acid and the carbonyl oxygen of caffeine with d(D⋯A) = 2.672 (2) Å. All other hydrogen bonds either involve crystal water or utilize protonated carbon atoms as donors.

【 授权许可】

CC BY