Department of Chemistry, Indian Institute of Technology Bombay, Powai, Mumbai 400076, India.
Chemistry. 2010 Jan 18;16(3):994-1009. doi: 10.1002/chem.200901994.
In contrast to the well-known reaction of phosphonic acids RP(O)(OH)(2) with divalent transition-metal ions that yields layered metal phosphonates RPO(3)M(H(2)O), the 2,6-diisopropylphenyl ester of phosphoric acid, dippH(2), reacts with zinc acetate in methanol under ambient conditions to afford tetrameric zinc phosphate (ArO)PO(3)Zn(MeOH) (1). The coordinated methanol in 1 can be readily exchanged by stronger Lewis basic ligands at room temperature. This strategy opens up a new avenue for building double-four-ring (D4R) cubane-based supramolecular assemblies through strong intercubane hydrogen-bonding interactions. Seventeen pyridinic ligands have been used to synthesize as many D4R cubanes (ArO)PO(3)Zn(L) (2-18) from 1. The ligands have been chosen in such a way that the majority of them contain an additional functional group that could be used for noncovalent synthesis of extended structures. When the ligand does not contain any other hydrogen-bonding donor-acceptor sites (e.g., 2,4,6-trimethylpyridine (collidine)), zero-dimensional D4R cubanes have been obtained. The use of pyridine, lutidine, 2-aminopyridine, and 2,6-diaminopyridine, however, results in the formation of linear or zigzag one-dimensional assemblies of D4R cubanes through strong intermolecular C-H...O or N-H...O interactions. Construction of two-dimensional assemblies of zinc phosphates has been achieved by employing 2-hydroxypyridine or 2-methylimidazole as the exo-cubane ligand on zinc centers. The introduction of an alcohol side chain on the pyridinic ligand in such a way that the -CH(2)OH group cannot participate in intracubane hydrogen bonding (e.g., pyridine-3-methanol, pyridine-4-methanol, and 3,5-dimethylpyrazole-N-ethanol) leads to the facile noncovalent synthesis of three-dimensional framework structures. Apart from being useful as building blocks for noncovalent synthesis of zeolite-like materials, compounds 1-18 can also be thermolyzed at approximately 500 degrees C to yield high-purity zinc pyrophosphate (Zn(2)P(2)O(7)) ceramic material.
与众所周知的二价过渡金属离子与膦酸 RP(O)(OH)(2) 的反应形成层状金属膦酸盐 RPO(3)M(H(2)O) 相反，磷酸的 2,6-二异丙基苯酯，二异丙基苯磷酸酯，在甲醇中与醋酸锌在环境条件下反应，得到四聚锌磷酸盐 (ArO)PO(3)Zn(MeOH) (1)。1 中配位的甲醇可以在室温下通过更强的路易斯碱性配体容易地交换。该策略为通过强的间-金属间氢键相互作用构建双四环（D4R）立方烷基超分子组装体开辟了新途径。十七个吡啶配体已被用于从 1 合成多达 17 个 D4R 立方烷 (ArO)PO(3)Zn(L) (2-18)。配体的选择方式是，它们中的大多数都包含可以用于非共价合成扩展结构的附加官能团。当配体不包含任何其他氢键给体-受体位点（例如 2,4,6-三甲基吡啶（吡啶））时，得到零维 D4R 立方烷。然而，使用吡啶、六氢吡啶、2-氨基吡啶和 2,6-二氨基吡啶，会导致通过强的分子间 C-H...O 或 N-H...O 相互作用形成 D4R 立方烷的线性或锯齿形一维组装体。通过使用 2-羟基吡啶或 2-甲基咪唑作为锌中心的外立方烷配体，实现了锌磷酸盐的二维组装体的构建。以使得-CH(2)OH 基团不能参与立方烷内氢键的方式在吡啶配体上引入醇侧链（例如吡啶-3-甲醇、吡啶-4-甲醇和 3,5-二甲基吡唑-N-乙醇），导致易于非共价合成三维骨架结构。除了作为沸石样材料的非共价合成的有用构建块外，化合物 1-18 还可以在约 500°C 下热解，得到高纯锌焦磷酸盐 (Zn(2)P(2)O(7)) 陶瓷材料。
