Reinvestigation of tricyclic acyclovir: characterization of a `proton-wire' model

• Published in: Acta crystallographica. Section C, Crystal structure communications Vol. 69; no. 9; pp. 1077 - 1080
• Main Authors: Meepripruk, Montha, Haller, Kenneth J.
• Format: Journal Article
• Language: English
• Published: 5 Abbey Square, Chester, Cheshire CH1 2HU, England International Union of Crystallography 01.09.2013; Wiley Subscription Services, Inc
• Subjects: acyclovir; Acyclovir - chemistry; Asymmetry; Chemical compounds; Crystal structure; Crystallography; Crystallography, X-Ray; Disorders; Gramicidin - chemistry; Hydrogen Bonding; Hydrogen bonds; Imidazoles - chemistry; Inversions; Mathematical models; Molecules; proton wires; Purines - chemistry; Solvents - chemistry; Three dimensional; Water - chemistry; water clusters; Wire; crystal structure; acyclovir; water clusters; proton wires
• ISSN: 0108-2701; 1600-5759
• DOI: 10.1107/S0108270113021082

The crystal structure of a dihydrate of the title compound, 3‐[(2‐hydroxyethoxy)methyl]‐6‐methyl‐3H‐imidazolo[1,2‐a]‐purin‐9(5H)‐one, C11H13N5O3·2H2O, has been reinvestigated. The asymmetric unit contains two molecules of tricyclic acyclovir and four molecules of water. The structure consists of a three‐dimensional network of strong hydrogen bonds that integrates all of the components. While the crystal structure and the formation of an (H2O)8 solvent water molecule cluster through a disordered strong hydrogen bond [O...O = 2.807 (3) Å] between two water molecules across an inversion centre has been described previously [Suwińska, Golankiewicz & Zielenkiewicz (2001). Acta Cryst. C57, 767–769], the disorder was incompletely modelled. In this work, the disorder model is extended and includes disorder of one tricyclic acyclovir hydroxy group across another inversion centre [O...O = 2.644 (4) Å]. The resulting infinite O—H...O hydrogen‐bonded water–hydroxy chains, analogous to the `proton wires' found in the membrane protein gramicidin A, are discussed and an unusual disorder model involving infinite concerted chains of O—H...O hydrogen bonds is provided.