HOST-GUEST COMPLEXATION .62. SOLVOPHOBIC AND ENTROPIC DRIVING FORCES FOR FORMING VELCRAPLEXES, WHICH ARE 4-FOLD, LOCK-KEY DIMERS IN ORGANIC MEDIA
HOST-GUEST COMPLEXATION .62. SOLVOPHOBIC AND ENTROPIC DRIVING FORCES FOR FORMING VELCRAPLEXES, WHICH ARE 4-FOLD, LOCK-KEY DIMERS IN ORGANIC MEDIA
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DOI：
10.1021/ja00046a022
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发表时间：
1992-09-23
影响因子：
15
通讯作者：
KNOBLER, CB
中科院分区：
文献类型：
--
作者：
CRAM, DJ;CHOI, HJ;KNOBLER, CB
已经制备了由芳族基团组成的系统，所述芳族基团刚性排列以形成约15乘约20埃的矩形表面，所述矩形表面包含在3点钟和9点钟处的两个规则间隔的突出甲基和在12点钟和6点钟处的两个甲基大小的孔（例如，1）。这些分子形成具有大的公共表面的二聚体，其中四个甲基插入到四个孔中。所得复合物在货车德瓦耳斯距离+0.2埃处具有82至132个分子间原子间接触（五种晶体结构）。乙基或氢取代中心芳基甲基消除络合。八个取代基连接在外围的单体延伸的表面和深刻影响的结合自由能（-Δ G度值）的复合物，其范围从9千卡摩尔-1在CDCl 3在温度-30至25 ℃。具有旋转自由度的外围取代基抑制同二聚化。rive二聚化的活化自由能（Δ G双刃剑）范围为8至10 kcal mol-1，5个解离为10至15 kcal mol-1（在CDCl 3中），表明它们的过渡态是非常差的溶剂化。的-DELTA-G-度的值与显着的例外，二聚溶剂的极性和极化率显着增加。焓（Δ H值）范围为+6至-8 kcal mol-1，熵（Δ S值）范围为-6至+40 cal mol-1 K-1。一些二聚反应是熵驱动的，焓相反，指向有机介质中的大疏溶剂效应。
Systems have been prepared composed of aromatic groups rigidly arranged to form approximately 15 by approximately 20 angstrom rectangular surfaces containing two regularly spaced protruding methyls at 3 and 9 o'clock and two methyl-sized holes at 12 and 6 o'clock (e.g., 1). These molecules form dimers with large common surfaces in which the four methyl groups insert into the four holes. The resulting complexes have 82 to 132 intermolecular atom-to-atom contacts at van der Waals distances +0.2 angstrom (five crystal structures). Substitution of ethyls or hydrogens for the central aryl methyls eliminates complexation. Eight substituents attached at the periphery of the monomers extend the surfaces and profoundly affect the binding free energies (-DELTA-G-degrees values) of the complexes, which range from 9 kcal mol-1 in CDCl3 at temperatures -30 to 25-degrees-C. Peripheral substituents with rotational degrees of freedom inhibit homodimerization. Activation free energies (DELTA-G double dagger) for rive dimerizations ranged from 8 to 10 kcal mol-1 and for five dissociations from 10 to 15 kcal mol-1 (in CDCl3), suggesting their transition states to be very poorly solvated. The-DELTA-G-degrees values for dimerization with notable exceptions increased dramatically with solvent polarity and polarizability. Enthalpies (DELTA-H values) ranged from +6 to -8 kcal mol-1 and entropies (DELTA-S values) from -6 to +40 cal mol-1 K-1. Some dimerizations were entropy driven and enthalpy opposed, pointing to large solvophobic effects in organic media.