Sridhar Balasubramanian
Laboratory of X-ray Crystallography, Indian Institute of Chemical Technology, Hyderabad 500 007, India.
Acta Crystallogr C. 2011 Oct;67(Pt 10):o382-6. doi: 10.1107/S0108270111036493. Epub 2011 Sep 15.
In xanthinium nitrate hydrate [systematic name: 2,6-dioxo-1,2,3,6-tetrahydro-9H-purin-7-ium nitrate monohydrate], C(5)H(5)N(4)O(2)(+)·NO(3)(-)·H(2)O, (I), and xanthinium hydrogen sulfate hydrate [systematic name: 2,6-dioxo-1,2,3,6-tetrahydro-9H-purin-7-ium hydrogen sulfate monohydrate], C(5)H(5)N(4)O(2)(+)·HSO(4)(-)·H(2)O, (II), the xanthine molecules are protonated at the imine N atom with the transfer of an H atom from the inorganic acid. The asymmetric unit of (I) contains a xanthinium cation, a nitrate anion and one water molecule, while that of (II) contains two crystallographically independent xanthinium cations, two hydrogen sulfate anions and two water molecules. A pseudo-quadruple hydrogen-bonding motif is formed between the xanthinium cations and the water molecules via N-H···O and O-H···O hydrogen bonds in both structures, and leads to the formation of one-dimensional polymeric tapes. These cation-water tapes are further connected by the respective anions and aggregate into two-dimensional hydrogen-bonded sheets in (I) and three-dimensional arrangements in (II).
在硝酸黄嘌呤水合物[系统名称：2,6 - 二氧代 - 1,2,3,6 - 四氢 - 9H - 嘌呤 - 7 - 鎓硝酸盐一水合物]，C(5)H(5)N(4)O(2)(+)·NO(3)(-)·H(2)O，(I)，以及硫酸氢黄嘌呤水合物[系统名称：2,6 - 二氧代 - 1,2,3,6 - 四氢 - 9H - 嘌呤 - 7 - 鎓硫酸氢盐一水合物]，C(5)H(5)N(4)O(2)(+)·HSO(4)(-)·H(2)O，(II)中，黄嘌呤分子在亚胺N原子处质子化，同时有一个H原子从无机酸转移过来。(I)的不对称单元包含一个黄嘌呤阳离子、一个硝酸根阴离子和一个水分子，而(II)的不对称单元包含两个晶体学独立的黄嘌呤阳离子、两个硫酸氢根阴离子和两个水分子。在这两种结构中，通过N - H···O和O - H···O氢键在黄嘌呤阳离子和水分子之间形成了一个准四重氢键基序，并导致形成一维聚合物带。这些阳离子 - 水带通过各自的阴离子进一步连接，并在(I)中聚集成二维氢键片层，在(II)中形成三维排列。
