THE GEOMETRY OF CALCIUM-CARBOXYLATE INTERACTIONS IN CRYSTALLINE COMPLEXES
THE GEOMETRY OF CALCIUM-CARBOXYLATE INTERACTIONS IN CRYSTALLINE COMPLEXES
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DOI：
10.1107/s0567740881005037
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发表时间：
1981-01-01
期刊：
影响因子：
--
通讯作者：
BUGG, CE
中科院分区：
文献类型：
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作者：
EINSPAHR, H;BUGG, CE
从钙配合物的晶体结构中综述了约170例钙-羧酸盐相互作用的几何结构。钙与羧酸盐的相互作用主要分为三大类：一种不确定模式，即Ca离子只与羧酸盐O原子中的一个结合；双齿模式，其中羧酸离子使用两个O原子来螯合Ca离子；以及另一种螯合模式，即a模式，当Ca离子的合适配体附着在a位置时观察到，并且通过使用ct取代基与羧酸O原子之一实现Ca离子的螯合。这三种模式表现出不同的几何偏好，但在每一种模式中，钙离子都有靠近羧酸基平面的强烈倾向。一般来说，Ca离子与CO键共线的趋势不大。未识别的例子聚集在CO键的两侧，大多数Ca离子位于羧酸基第二个O原子的Ca- OC角约为150-170的一侧，或位于第二个O原子的110-140的一侧。以双齿模式结合的Ca离子通过与羧酸基的两个O原子相互作用而被限制在一个受限区域内；这些钙离子的Ca- OC角约为90。在ct螯合模式下，Ca离子被限制在Ca- OC角约为110-130的狭窄区域内。Ca—O距离与Ca—OC角有明显的相关关系；Ca- O距离较短的例子往往是Ca- OC角更接近线性的例子。
The geometries of some 170 examples of calcium-carboxylate interactions from crystal structures of calcium complexes are reviewed. Calcium-carboxylate interactions fall into three main categories: a unidentate mode in which the Ca ion binds to only one of the carboxylate O atoms; a bidentate mode in which the carboxylate ion uses both O atoms to chelate the Ca ion; and an additional chelation mode, the a mode, that is observed when a suitable ligand for the Ca ion is attached at the a position and in which chelation of the Ca ion is achieved by use of the ct substituent together with one of the carboxylate O atoms. The three modes show distinct geometrical preferences, but in each there is a strong tendency for the Ca ion to lie near the plane of the carboxylate group. In general, there is little tendency for a Ca ion to be collinear with the CO bond. The unidentate examples cluster on both sides of the CO bond, with most Ca ions lying at Ca--OC angles of about 150-170 on the side away from the second O atom of the carboxylate group, or 110-140 on the side toward the second O atom. The Ca ions bound in the bidentate mode are confined to a restricted region by interactions with both O atoms of the carboxylate groups; these Ca ions occur at Ca--OC angles of about 90. In the ct-chelation mode, Ca ions are restricted to a narrow region with Ca--OC angles of about 110-130. There is an apparent correlation between Ca--O distance and Ca--OC angle; exam-ples with shorter Ca--O distances tend to be those with more nearly linear Ca--OC angles.