Coordination polymers with pyridine-2,4,6-tricarboxylic acid and alkaline-earth/lanthanide/transition metals: synthesis and X-ray structures
作者:Madhab C. Das、Sujit K. Ghosh、E. Carolina Sañudo、Parimal K. Bharadwaj
DOI:10.1039/b814066a
日期:——
Pyridine-2,4,6-tricarboxylic acid (ptcH3) reacts with Cd(II), Mn(II), Ni(II), Mg(II), Ca(II), Sr(II), Ba(II), Dy(III) salts forming different products depending on the reaction conditions. In the presence of pyridine at room temperature the acetate, chloride or nitrate salt of Cd(II) breaks the ligand to form an open framework structure with the empirical formula, [Cd(Ox)(H2O)2]H2O}n (Ox = oxalate), 1. In the absence of pyridine, no crystalline compound could be isolated at room temperature (RT). However, under hydrothermal conditions and in the absence of pyridine, a discrete tetrameric complex with the formula, [Cd2(cda)2(H2O)4](H2O)3}2 (cdaH2 = 4-hydroxypyridine-2,6-dicarboxylic acid), 2, is formed where the carboxylate group at the 4-position of the ligand is reduced to a hydroxyl group. When Ni(II), Mn(II), Mg(II), Ca(II), Sr(II), Ba(II), Dy(III) salts are used in place of Cd(II), no crystalline product could be isolated at RT. But under hydrothermal conditions, coordination polymers ([Ni1.5(ptc)(pip)0.5(H2O)4]·H2O}n, (pip = piperazine), 3; Mn1.5(ptc)·2H2O}n, 4; Mg3(ptc)2·8H2O}n, 5; [Mg(ptc)(H2O)2]·1/2[Mg(H2O)6]·H2O}n, 6; Ca1.5(ptc)·2H2O}n, 7; Sr1.5(ptc)·5H2O}n, 8; [Ba(ptc)(H2O)][Ba(ptcH2)H2O]}n, 9; [Dy(ptc)·3H2O]·H2O}n, 10) are formed. The structures exhibit different dimensionality depending on the nature of the metal ions. In 1 a discrete acyclic water hexamer is also identified. All the compounds are characterized in the solid state by X-ray crystallography, IR and elemental analysis.
吡啶-2,4,6-三甲酸 (ptcH3) 与 Cd(II)、Mn(II)、Ni(II)、Mg(II)、Ca(II)、Sr(II)、Ba(II)、 Dy(III) 盐根据反应条件形成不同的产物。在室温下,在吡啶存在下,Cd(II) 的乙酸盐、氯化物或硝酸盐会破坏配体,形成开放式框架结构,其经验式为 [Cd(Ox)(H2O)2]H2O}n (Ox = 草酸盐),1. 在没有吡啶的情况下,在室温 (RT) 下无法分离出结晶化合物。然而,在水热条件下且不存在吡啶的情况下,会形成离散的四聚体复合物,其结构式为:[Cd2(cda)2(H2O)4](H2O)3}2 (cdaH2 = 4-羟基吡啶-2,6-二羧基)酸)2,是在配体4位上的羧酸根被还原为羟基时形成的。当使用 Ni(II)、Mn(II)、Mg(II)、Ca(II)、Sr(II)、Ba(II)、Dy(III) 盐代替 Cd(II) 时,不会产生结晶产物在 RT 处隔离。但在水热条件下,配位聚合物([Ni1.5(ptc)(pip)0.5(H2O)4]·H2O}n, (pip = 哌嗪), 3; Mn1.5(ptc)·2H2O}n, 4; Mg3(ptc)2·8H2O}n, 5; [Mg(ptc)(H2O)2]·1/2[Mg(H2O)6]·H2O}n, 6; )·2H2O}n, 7; Sr1.5(ptc)·5H2O}n, 8; [Ba(ptc)(H2O)][Ba(ptcH2)H2O]}n, 9;形成·3H2O]·H2O}n,10)。根据金属离子的性质,结构表现出不同的维度。在1中还鉴定出离散的无环水六聚体。所有化合物都通过 X 射线晶体学、红外和元素分析进行了固态表征。