title: Reinvestigation of tricyclic acyclovir: characterization of a 'proton-wire' model.
abstract: 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.
authors.affiliation: Schools of Chemistry and Biochemistry, Institute of Science, Suranaree University of Technology, Nakhon Ratchasima 30000, Thailand. montha_mee@hotmail.com
authors.forename: Montha
authors.initials: M
authors.lastname: Meepripruk
authors.forename: Kenneth J
authors.initials: KJ
authors.lastname: Haller
mesh_terms: D000212:Acyclovir / Q000737:chemistry*; D018360:Crystallography, X-Ray; D006096:Gramicidin / Q000737:chemistry*; D006860:Hydrogen Bonding; D007093:Imidazoles / Q000737:chemistry*; D011687:Purines / Q000737:chemistry*; D012997:Solvents / Q000737:chemistry; D014867:Water / Q000737:chemistry
chemical_list: C434352:3-((2-hydroxyethoxy)methyl)-6-methyl-3H-imidazolo(1,2-a)purin-9(5H)-one dihydrate; D007093:Imidazoles; D011687:Purines; D012997:Solvents; D014867:Water; D006096:Gramicidin; D000212:Acyclovir
keywords: acyclovir; crystal structure; proton wires; water clusters