Differing Patterns in the Self-Assembly of Radially Anchored Imidazoles, 1,3,5-Tris(1H-imidazol-2-yl)benzene and 1,3-Bis(1H-imidazol-2-yl)benzene
作者:Y. B. R. D. Rajesh、Subramania Ranganathan、Richard D. Gilardi、Isabella L. Karle
DOI:10.1007/s10870-007-9286-6
日期:2008.1
The novel 3-fold symmetric 1,3,5-tris(1H-imidazol-2-yl)benzene, having a propensity for a 3-fold salt formation by hydrogen bonding at the periphery, was prepared from oxidation of the hexahydro imidazole precursor. The transformation proved difficult and, of the many reagents tried, only barium manganate and o-iodoxy benzoic acid were successful. The oxidation to the aromatic 1,3,5-tris imidazolyl benzene produces dramatic changes, particularly when the X-ray structures of their tris-TFA (trifluoroacetic acid) salts are compared. While the hexahydro precursor exhibited a herringbone type arrangement in the crystal, the oxidation resulted in almost co-planar molecules that formed parallel stacks separated by 3.57 Å between the atoms in separate planes. 1,3-Bis(1H-imidazole-2-yl)benzene is an attractive core unit for assembly using a variety of auxiliaries. Several attempts to complex the bis-imidazole with organic acids failed. These efforts lead to the serendipitous discovery of a novel tetrameric assembly, mediated by water molecules, which was confirmed by crystallization of the bis imidazole from water. Differing Patterns in the Self-Assembly of Radially Anchored Imidazoles, 1,3,5-Tris(1 H -imidazol-2-yl)benzene and 1,3-Bis(1 H -imidazol-2-yl)benzene A. Infinite stacks of the TFA salt from 1,3,5-tris(1H-imidazol-2-yl)benzene with a separation of 3.57 Å between atoms in separate planes (The TFA moiety has been omitted for clarity). B. Tetrameric assembly of 1,3-bis(1H-imidazol-2-yl)benzene, mediated by water molecules. Differing Patterns in the Self-Assembly of Radially Anchored Imidazoles, 1,3,5-Tris(1 H -imidazol-2-yl)benzene and 1,3-Bis(1 H -imidazol-2-yl)benzene Y.B.R.D. Rajesh, (2) Subramania Ranganathan, (2)* Richard D. Gilardi (1,3) and Isabella L. Karle, (1)* (1) Laboratory for the Structure of Matter, Naval Research Laboratory, Washington, D.C. 20375-5341 (2) Discovery Laboratory, Organic III, Indian Institute of Chemical Technology, Hyderabad 500 007, India (3) Retired
新型 3 倍对称 1,3,5-三(1H-咪唑-2-基)苯是通过氧化六氢咪唑前体制备的,这种苯具有通过外围氢键形成 3 倍盐的倾向。这一转化过程十分困难,在尝试的多种试剂中,只有锰酸钡和邻碘氧基苯甲酸取得了成功。氧化成芳香族的 1,3,5-三咪唑苯会产生巨大的变化,尤其是在比较它们的三-TFA(三氟乙酸)盐的 X 射线结构时。六氢前体在晶体中呈现出人字形排列,而氧化则导致几乎共平面的分子形成平行堆叠,不同平面的原子之间相隔 3.57 Å 。1,3-双(1H-咪唑-2-基)苯是一种极具吸引力的核心单元,可使用多种辅助剂进行组装。曾多次尝试用有机酸络合双咪唑,但都以失败告终。这些努力导致偶然发现了一种由水分子介导的新型四聚体组装,并通过双咪唑从水中结晶得到证实。径向锚定咪唑、1,3,5-三(1H-咪唑-2-基)苯和 1,3-双(1H-咪唑-2-基)苯自组装的不同模式 A. 1,3,5-三(1H-咪唑-2-基)苯的反式脂肪酸盐的无限堆叠,不同平面上的原子间距为 3.57 埃(为清晰起见,省略了反式脂肪酸分子)。B. 1,3-双(1H-咪唑-2-基)苯在水分子介导下的四聚体组装。径向锚定咪唑、1,3,5-三(1 H-咪唑-2-基)苯和 1,3-双(1 H-咪唑-2-基)苯的自组装中的不同模式 Y.B.R.D. Rajesh, (2) Subramania Ranganathan, (2)* Richard D. Gilardi (1,3) 和 Isabella L.(1)* (1) 海军研究实验室物质结构实验室,华盛顿特区,20375-5341 (2)Discovery Laboratory, Organic III, Indian Institute of Chemical Technology, Hyderabad 500 007, India (3)Retired