Wiesbrock Frank, Schmidbaur Hubert
Anorganisch-chemisches Institut der Technischen Universität München, Lichtenbergstrasse 4, 85747 Garching, Germany.
Inorg Chem. 2003 Nov 3;42(22):7283-9. doi: 10.1021/ic034427t.
In an attempt to probe a potential template role of the large alkali-metal cations rubidium and cesium in the organization of biorelevant ligands, salicylate and anthranilate complexes of the two elements were prepared and structurally investigated. The studies were also expected to show the marked structural differences compared to the corresponding thallium(I) compounds. Rubidium anthranilate and cesium salicylate could be crystallized as the monohydrates Rb(Anth)(H(2)O) and Cs(Sal)(H(2)O). Both have layer structures containing the cations and the polar groups of the ligands in core domains sandwiched by the aromatic rings above and below. The metal atoms have coordination numbers 7 and 8, respectively, with an irregular coordination sphere made up exclusively of oxygen atoms. Crystalline material with a 1:2 stoichiometry, Cs[H(Anth)(2)], is obtained from aqueous solutions of Cs(Anth) upon absorption of carbon dioxide with concomitant formation of cesium bicarbonate, Cs(HCO(3)). The crystal structure of Cs(HCO(3)) was redetermined to obtain precise benchmark data for cesium carbonates and carboxylates. The cesium hydrogen bisanthranilate also has a layer structure with eight-coordinate cesium atoms. The coordination sphere includes one nitrogen donor atom. The organization of all layer structures appears to be governed mainly by steric effects and electrostatic forces with very little directional influence of the cations. This result suggests that the large alkali metals have no efficient template effect for the organization of biological substrates and can explain the low toxicity of rubidium and cesium salts.
为了探究大碱金属阳离子铷和铯在生物相关配体组织中的潜在模板作用，制备了这两种元素的水杨酸盐和邻氨基苯甲酸盐配合物并进行了结构研究。这些研究还预期显示出与相应的铊（I）化合物相比显著的结构差异。铷邻氨基苯甲酸盐和铯水杨酸盐可以结晶为一水合物Rb(Anth)(H₂O)和Cs(Sal)(H₂O)。两者都具有层状结构，在核心区域包含阳离子和配体的极性基团，被上下的芳香环夹在中间。金属原子的配位数分别为7和8，其不规则的配位球仅由氧原子组成。通过吸收二氧化碳并伴随形成碳酸氢铯Cs(HCO₃)，从Cs(Anth)的水溶液中获得化学计量比为1:2的晶体材料Cs[H(Anth)₂]。重新测定了Cs(HCO₃)的晶体结构以获得碳酸铯和羧酸盐的精确基准数据。铯氢双邻氨基苯甲酸盐也具有层状结构，其中铯原子为八配位。配位球包括一个氮供体原子。所有层状结构的组织似乎主要受空间效应和静电力控制，阳离子的定向影响很小。这一结果表明，大碱金属对生物底物的组织没有有效的模板效应，并且可以解释铷盐和铯盐的低毒性。
