Kong Xiang-Jian, Long La-Sheng, Zheng Lan-Sun, Wang Ruiyao, Zheng Zhiping
State Key Laboratory of Physical Chemistry of Solid Surface and Department of Chemistry, College of Chemistry and Chemical Engineering, Xiamen University, Xiamen 361005, China.
Inorg Chem. 2009 Apr 6;48(7):3268-73. doi: 10.1021/ic802357m.
Polynuclear lanthanide hydroxide complexes featuring the cubane-like Ln(4)(mu(3)-OH)(4) [Ln = Eu(III), Gd(III)] cluster core have been synthesized by controlled hydrolysis of the lanthanide ions using nicotinic acid as the ancillary ligand. The synthetic procedure has been found to significantly influence the nature of the resulting cluster species. In a one-pot synthesis, adjusting the pH of the reaction mixture containing Ln(ClO(4))(3) and nicotinic acid afforded tetranuclear complexes of the general formula Ln(4)(mu(3)-OH)(4)(Hnic)(5)(H(2)O)(12)(8) with the Ln(4)(mu(3)-OH)(4) (Ln = Eu, Gd) cluster core encapsulated by zwitterionic nicotinate ligands. In stark contrast, mixing aqueous solutions of Ln(ClO(4))(3) and nicotinic acid whose pH had been preadjusted produced assemblies composed of two of the cubane-like cluster cores that are related by a crystallographic inversion center and are doubly bridged by nicotinate ligands using both the carboxylate group and pyridyl N atom for coordination. The influences of pH conditions and synthetic procedures on the identity of the resulting cluster species are discussed, so is the structural relevance of the low-pH complexes to their cluster analogues obtained under higher-pH conditions.
以烟酸作为辅助配体，通过镧系离子的控制水解合成了具有类立方烷型Ln(4)(μ(3)-OH)(4) [Ln = Eu(III)，Gd(III)]簇核的多核氢氧化镧系配合物。已发现合成过程会显著影响所得簇物种的性质。在一锅法合成中，调节含有Ln(ClO(4))(3)和烟酸的反应混合物的pH值，得到通式为Ln(4)(μ(3)-OH)(4)(Hnic)(5)(H(2)O)(12)(8)的四核配合物，其Ln(4)(μ(3)-OH)(4)（Ln = Eu，Gd）簇核被两性离子烟酸酯配体包裹。与之形成鲜明对比的是，将预先调节好pH值的Ln(ClO(4))(3)和烟酸的水溶液混合，得到了由两个类立方烷簇核组成的组装体，这两个簇核通过一个晶体学反演中心相关联，并由烟酸酯配体利用羧酸根基团和吡啶基N原子进行配位而双重桥连。讨论了pH条件和合成过程对所得簇物种身份的影响，以及低pH配合物与其在较高pH条件下获得的簇类似物的结构相关性。
