Institut für Organische Chemie, RWTH Aachen University , Landoltweg 1, Aachen 52074, Germany.
Institut für Chemie und Biochemie-Organische Chemie, Freie Universität Berlin , Takustrasse 3, Berlin 14195, Germany.
J Am Chem Soc. 2017 Nov 22;139(46):16959-16966. doi: 10.1021/jacs.7b10098. Epub 2017 Nov 8.
London dispersion forces are the weakest interactions between molecules. Because of this, their influence on chemical processes is often low, but can definitely not be ignored, and even becomes important in cases of molecules with large contact surfaces. Hierarchically assembled dinuclear titanium(IV) helicates represent a rare example in which the direct observation of London dispersion forces is possible in solution even in the presence of strong cohesive solvent effects. Hereby, the dispersion forces do not unlimitedly support the formation of the dimeric complexes. Although they have some favorable enthalpic contribution to the dimerization of the monomeric complex units, large flexible substituents become conformationally restricted by the interactions leading to an entropic disadvantage. The dimeric helicates are entropically destabilized.
伦敦色散力是分子之间最微弱的相互作用力。由于这一点，它们对化学过程的影响通常较低，但绝不能忽视，甚至在分子具有较大接触表面的情况下变得重要。分级组装的双核钛（IV）螺旋体代表了一个罕见的例子，即使在存在强凝聚溶剂效应的情况下，也可以在溶液中直接观察到伦敦色散力。在此，色散力不会无限地支持二聚体复合物的形成。尽管它们对单体配合物单元的二聚化有一些有利的焓贡献，但大的柔性取代基会受到相互作用的限制，导致熵不利。二聚螺旋体的熵是不稳定的。
