Smith Graham, Wermuth Urs D
Science and Engineering Faculty, Queensland University of Technology, GPO Box 2434, Brisbane, Queensland 4001, Australia.
School of Natural Sciences, Griffith University, Nathan, Queensland 4111, Australia.
Acta Crystallogr C Struct Chem. 2017 Jan 1;73(Pt 1):61-67. doi: 10.1107/S2053229616019434.
(4-Aminophenyl)arsonic acid (p-arsanilic acid) is used as an antihelminth in veterinary applications and was earlier used in the monosodium salt dihydrate form as the antisyphilitic drug atoxyl. Examples of complexes with this acid are rare. The structures of the alkaline earth metal (Mg, Ca, Sr and Ba) complexes with (4-aminophenyl)arsonic acid (p-arsanilic acid) have been determined, viz. hexaaquamagnesium bis[hydrogen (4-aminophenyl)arsonate] tetrahydrate, Mg(HO)·4HO, (I), catena-poly[[[diaquacalcium]-bis[μ-hydrogen (4-aminophenyl)arsonato-κO:O']-[diaquacalcium]-bis[μ-hydrogen (4-aminophenyl)arsonato-κO:O]] dihydrate], {[Ca(CHAsNO)(HO)]·2HO}, (II), catena-poly[[triaquastrontium]-bis[μ-hydrogen (4-aminophenyl)arsonato-κO:O']], [Sr(CHAsNO)(HO)], (III), and catena-poly[[triaquabarium]-bis[μ-hydrogen (4-aminophenyl)arsonato-κO:O']], [Ba(CHAsNO)(HO)], (IV). In the structure of magnesium salt (I), the centrosymmetric octahedral [Mg(HO)] cation, the two hydrogen p-arsanilate anions and the four water molecules of solvation form a three-dimensional network structure through inter-species O-H and N-H hydrogen-bonding interactions with water and arsonate O-atom and amine N-atom acceptors. In one-dimensional coordination polymer (II), the distorted octahedral CaO coordination polyhedron comprises two trans-related water molecules and four arsonate O-atom donors from bridging hydrogen arsanilate ligands. One bridging extension is four-membered via a single O atom and the other is eight-membered via O:O'-bridging, both across inversion centres, giving a chain coordination polymer extending along the [100] direction. Extensive hydrogen-bonding involving O-H...O, O-H...N and N-H...O interactions gives an overall three-dimensional structure. The structures of the polymeric Sr and Ba complexes (III) and (IV), respectively, are isotypic and are based on irregular MO coordination polyhedra about the M centres, which lie on twofold rotation axes along with one of the coordinated water molecules. The coordination centres are linked through inversion-related arsonate O:O'-bridges, giving eight-membered ring motifs and forming coordination polymeric chains extending along the [100] direction. Inter-chain N-H...O and O-H...O hydrogen-bonding interactions extend the structures into three dimensions and the crystal packing includes π-π ring interactions [minimum ring centroid separations = 3.4666 (17) Å for (III) and 3.4855 (8) Å for (IV)].
（4-氨基苯基）胂酸（对氨基苯胂酸）在兽医领域用作抗蠕虫药，早期曾以二水合单钠盐形式作为抗梅毒药物阿托克西尔使用。与这种酸形成的配合物的例子很少见。已确定了碱土金属（镁、钙、锶和钡）与（4-氨基苯基）胂酸（对氨基苯胂酸）形成的配合物的结构，即六水合镁双[氢（4-氨基苯基）胂酸根]四水合物，Mg(H₂O)₆₂·4H₂O，（I）；链状聚[[[二水合钙]-双[μ-氢（4-氨基苯基）胂酸根-κO:O']-[二水合钙]-双[μ-氢（4-氨基苯基）胂酸根-κO:O]]二水合物]，{[Ca(C₆H₇AsNO₃)(H₂O)₂]·2H₂O}，（II）；链状聚[[三水合锶]-双[μ-氢（4-氨基苯基）胂酸根-κO:O']]，[Sr(C₆H₇AsNO₃)(H₂O)₃]，（III）；以及链状聚[[三水合钡]-双[μ-氢（4-氨基苯基）胂酸根-κO:O']]，[Ba(C₆H₇AsNO₃)(H₂O)₃]，（IV）。在镁盐（I）的结构中，中心对称的八面体[Mg(H₂O)₆]²⁺阳离子、两个氢对氨基苯胂酸根阴离子和四个溶剂化水分子通过物种间的O-H和N-H氢键相互作用与水以及胂酸根O原子和胺N原子受体形成三维网络结构。在一维配位聚合物（II）中，扭曲的八面体CaO配位多面体包含两个反式相关的水分子和来自桥连氢胂酸根配体的四个胂酸根O原子供体。一个桥连延伸通过单个O原子形成四元环，另一个通过O:O'桥连形成八元环，两者都跨越对称中心，形成沿[100]方向延伸的链状配位聚合物。涉及O-H...O、O-H...N和N-H...O相互作用的广泛氢键形成了整体的三维结构。聚合物锶和钡配合物（III）和（IV）的结构分别是同型的，基于围绕M中心的不规则MO配位多面体，M中心与其中一个配位水分子位于二重旋转轴上。配位中心通过与对称相关的胂酸根O:O'桥连相连，形成八元环基序并形成沿[100]方向延伸的配位聚合物链。链间N-H...O和O-H...O氢键相互作用将结构扩展到三维，晶体堆积包括π-π环相互作用[（III）的最小环质心间距 = 3.4666 (17) Å，（IV）的最小环质心间距 = 3.4855 (8) Å]。
