摘要
在生理及更高pH下以α-氨基酸或EDTA作为配体,抑制Ln(Ⅲ)水解得到了一类镧系元素-羟基自组装多核配合物.该类多核配合物以具有类立方烷结构的[Ln_4(μ_3-OH)_4]^(8+)为基本结构单元,可以单体{[Ln_4(μ_3-OH)_4]^(8+)},共顶点的“环状四聚体”{[Ln_(12)(μ_N-OH)_(16)~](20+)}或“环状五聚体{[Ln_(15)(μ_3-OH)_(20)]^(25+)}的形式稳定存在.本文报道了该类配合物的合成、结构及性质,探讨了卤素离子对“环状四聚体”及“环状五聚体’形成的模板效应,并初步证明了类立方烷结构单体,“环状四聚体”及“环状五聚体”乃是生理及更高pH下镧系元素的稳定存在形式.同时还证明了直接水解镧系元素硝酸盐或高氯酸盐能得到一类以正八面体结构的[Ln_6(μ_6-O)(μ_3-OH)_8」^(8+)为骨架的多核配合物.磁性测定表明,室温下各配合物的类立方烷结构中的镧系离子间无明显磁交换.
High - nuclearity lanthanide - hydroxo complexes were prepared via limited hydrolysis of lan-thanides using α - amino acids or EDTA as supporting ligands. These novel substances, synthesized under physiological or even higher- pH conditions, exist as tetranuclear cuboid [Ln4(μ3 - OH)4]8+ core - containing clusters. With appropriate halide templates, 'wheel - like' supramolecular structures composed of four or five vertex - sharing [Ln4(μ3 - OH)4]8+ units are formed. The face - capped octahedral [Ln6(μ6 -O) (μ3 -OH)8]8 + cluster centering on an interstitial μ6 -O ligand is another stable form of lanthanide - hydroxo complexes and can be self - assembled via direct hydrolysis of lanthanide nitrates and perchlorates. The significant influence of pH conditions on lanthanide coordination chemistry is further illustrated by a new paradigmatic lanthanide- EDTA chemistry, wherein unprecedented multinuclear Ln - EDTA cluster complexes are realized.
出处
《化学学报》
SCIE
CAS
CSCD
北大核心
2000年第12期1481-1492,共12页
Acta Chimica Sinica
基金
美国亚利桑那大学
Research Corporation
美国化学会PRF以及中国国家攀登计划资助
关键词
镧系元素
氨基酸
羟基
多核配合物
类立方烷结构
lanthanide complexes, amino acid complexes, hydroxo complexes, cuboid structure, hydrolysis, template effects
