AAA-DDD Triple Hydrogen Bond Complexes
AAA-DDD Triple Hydrogen Bond Complexes
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DOI：
10.1021/ja906061v
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发表时间：
2009-10-07
影响因子：
15
通讯作者：
Slawin, Alexandra M. Z.
中科院分区：
文献类型：
--
作者：
Blight, Barry A.;Camara-Campos, Amaya;Slawin, Alexandra M. Z.
实验和理论都表明，氢键受体（A）和供体（D）的AAA-DDD模式是三个相邻氢键中心的排列，导致两个物种之间的最强缔合。Murray和齐默尔曼制备了这种体系的第一个实施例（配合物3圆2），并通过H-1 NMR光谱法确定其在CDCl 3中的缔合常数（K-a）的下限为10（5）M-1（Murray，T. J.道：齐默尔曼，S. C. J Am. 1992，114，4010-4011）。第一个阳离子AAA-DDD对（3圈4（+））由Bell和Anslyn（Bell，D.一、Anslyn，E. A. Tetrahedron 1995，51，7161-7172），其中在CH 2Cl 2中的K-a > 5 × 10（5）M-1，如通过紫外-可见光谱测定的。我们最近能够使用化学上更稳定的AAA-DDD体系6 circle 2来量化中性AAA-DDD排列的强度，该体系在CH 2Cl 2中的缔合常数为2 × 10（7）M-1（Djurdjevic，S.;利，D。一、McNab，H.; Parsons，S.; Teobaldi，G.; Zerbetto，F. J. Am. 2007，129，476-477）。在这里，我们报告了更多的AA（A）和DDD合作伙伴，以及第一次精确测量阳离子AAA-DDD物质的缔合常数。配合物6环10（+）[B（3，5-（CF 3）（2）C6 H3）（4）（-）]在室温下在CH 2Cl 2中具有K-a = 3 × 10（10）M-1，是迄今为止测得的结合最强的三重氢键系统。具有BPh 4-抗衡阴离子的6个环10（+）的X射线晶体结构显示出三个短的（N（H）在棒中心点（N）在棒距离1.95-2.15埃下）、平行（但交错而不是严格线性; N-H中心点N角165.4-168.8度）、初级氢键的平面阵列。正如理论预测的那样，这些显然是通过每个质子和相邻初级氢键的受体原子之间的紧密静电相互作用（棒-中心点下的N（H）-棒距离2.78-3.29埃下的N）来加强的。
Experiment and theory both suggest that the AAA-DDD pattern of hydrogen bond acceptors (A) and donors (D) is the arrangement of three contiguous hydrogen bonding centers that results in the strongest association between two species. Murray and Zimmerman prepared the first example of such a system (complex 3 circle 2) and determined the lower limit of its association constant (K-a) in CDCl3 to be 10(5) M-1 by H-1 NMR spectroscopy (Murray, T. J.; Zimmerman, S. C. J Am. Chem. Soc. 1992, 114, 4010-4011). The first cationic AAA-DDD pair (3 circle 4(+)) was described by Bell and Anslyn (Bell, D. A.; Anslyn, E. A. Tetrahedron 1995, 51, 7161-7172), with a K-a > 5 x 10(5) M-1 in CH2Cl2 as determined by UV-vis spectroscopy. We were recently able to quantify the strength of a neutral AAA-DDD arrangement using a more chemically stable AAA-DDD system, 6 circle 2, which has an association constant of 2 x 10(7) M-1 in CH2Cl2 (Djurdjevic, S.; Leigh, D. A.; McNab, H.; Parsons, S.; Teobaldi, G.; Zerbetto, F. J. Am. Chem. Soc. 2007, 129, 476-477). Here we report on further AA(A) and DDD partners, together with the first precise measurement of the association constant of a cationic AAA-DDD species. Complex 6 circle 10(+)[B(3,5-(CF3)(2)C6H3)(4)(-)] has a K-a = 3 x 10(10) M-1 at RT in CH2Cl2, by far the most strongly bound triple hydrogen bonded system measured to date. The X-ray crystal structure of 6 circle 10(+) with a BPh4- counteranion shows a planar array of three short (N (H) under bar center dot center dot center dot (N) under bar distances 1.95-2.15 angstrom), parallel (but staggered rather than strictly linear; N-H center dot center dot center dot N angles 165.4-168.8 degrees), primary hydrogen bonds. These are apparently reinforced, as theory predicts, by close electrostatic interactions (N (H) under bar- center dot -(N) under bar distances 2.78-3.29 angstrom) between each proton and the acceptor atoms of the adjacent primary hydrogen bonds.