Polásek Miloslav, Sedinová Miroslava, Kotek Jan, Vander Elst Luce, Muller Robert N, Hermann Petr, Lukes Ivan
Department of Inorganic Chemistry, Charles University, Hlavova 2030, 128 40 Prague 2, Czech Republic.
Inorg Chem. 2009 Jan 19;48(2):455-65. doi: 10.1021/ic801596v.
Two macrocyclic ligands derived from H4dota containing three acetate pendant arms and one 2-methylpyridine-N-oxide coordinating unit were synthesized. The ligand H3do3apy(NO) (H3L1, 10-[(1-oxidopyridin-2-yl)methyl]-1,4,7,10-tetraazacyclododecane-1,4,7-triacetic acid) contains an unsubstituted pyridine-N-oxide ring; the ligand H4do3apy(NO-C) (H4L2, 10-[(4-carboxy-1-oxidopyridin-2-yl)methyl]-1,4,7,10-tetraazacyclododecane-1,4,7-triacetic acid) is functionalized with a carboxylic group in the 4 position of the pyridine ring to allow attachment to other molecules. The ligands form octadentate (N4O4 environment) Ln(III) complexes, with one water molecule completing the coordination sphere in a capping position. The complexes are present in solution exclusively as square-antiprismatic isomers over the whole lanthanide series. The introduction of the carboxylic group to the pyridine-N-oxide unit in H4L2 has no significant effect on the hydration number (q = 1) and the water exchange rate of the [Gd(H2O)(L2)]- complex compared to the parent [Gd(H2O)(L1)] complex (water residence times: tauM = 39 ns for [Gd(H2O)(L1)] and tauM = 34 ns for [Gd(H2O)(L2)]- at 298 K).
合成了两种源自H4dota的大环配体，它们含有三个乙酸酯侧链臂和一个2-甲基吡啶-N-氧化物配位单元。配体H3do3apy(NO)（H3L1，10-[(1-氧化吡啶-2-基)甲基]-1,4,7,10-四氮杂环十二烷-1,4,7-三乙酸）含有一个未取代的吡啶-N-氧化物环；配体H4do3apy(NO-C)（H4L2，10-[(4-羧基-1-氧化吡啶-2-基)甲基]-1,4,7,10-四氮杂环十二烷-1,4,7-三乙酸）在吡啶环的4位用羧基官能化，以便与其他分子连接。这些配体形成八齿（N4O4环境）Ln(III)配合物，一个水分子在封端位置完成配位球。在整个镧系元素系列中，这些配合物在溶液中仅以方形反棱柱异构体形式存在。与母体[Gd(H2O)(L1)]配合物相比，在H4L2的吡啶-N-氧化物单元中引入羧基对[Gd(H2O)(L2)]-配合物的水合数（q = 1）和水交换速率没有显著影响（水停留时间：在298 K时，[Gd(H2O)(L1)]的τM = 39 ns，[Gd(H2O)(L2)]-的τM = 34 ns）。
