Trevisan Lucia, Bond Andrew D, Hunter Christopher A
Yusuf Hamied Department of Chemistry, University of Cambridge, Lensfield Road, Cambridge CB2 1 EW, U.K.
J Am Chem Soc. 2025 Jan 8;147(1):1319-1326. doi: 10.1021/jacs.4c15767. Epub 2024 Dec 18.
Cooperativity between H-bonding interactions in networks is a fundamental aspect of solvation and self-assembly in molecular systems. The interaction of a series of bisphenols, which make an intramolecular H-bond between the two hydroxyl groups, and quinuclidine was used to quantify cooperativity in three-component networks. The presence of the intramolecular H-bond in the bisphenols was established by using H NMR spectroscopy in solution and X-ray crystallography in the solid state. The interactions with quinuclidine were investigated using UV-vis and H NMR titrations, which show that the intramolecular hydrogen bonds persist in the 1:1 complexes. By varying substituents on one of the phenol groups, it was possible to measure the effect of changing the strength of the intramolecular H-bond between the hydroxyl groups on the strength of the intermolecular H-bond with quinuclidine. Strong positive cooperativity was observed between the two interactions, with increases in binding free energy of up to 16 kJ mol. By varying substituents on the other phenol group, which makes both an intramolecular H-bond and an intermolecular H-bond in the complex, it was possible to measure how the properties of this central hydroxyl group modulate cooperativity between the interactions with the other two functional groups. Changing the polarity of this phenol had no effect on the measured cooperativity. The results indicate that cooperativity in H-bond networks can be understood as a polar interaction between two remote functional groups that is damped by a central functional group. The extent of damping is quantified by cooperativity parameter κ, which is 0.33 for the hydroxyl group and appears to be an intrinsic property of the geometry or polarizability of the functional group rather than polarity.
网络中氢键相互作用之间的协同性是分子系统中溶剂化和自组装的一个基本方面。一系列在两个羟基之间形成分子内氢键的双酚与奎宁环的相互作用被用于量化三元网络中的协同性。通过溶液中的核磁共振氢谱和固态的X射线晶体学确定了双酚中分子内氢键的存在。使用紫外可见光谱和核磁共振氢谱滴定研究了与奎宁环的相互作用，结果表明分子内氢键在1:1配合物中持续存在。通过改变其中一个酚羟基上的取代基，可以测量改变羟基之间分子内氢键强度对与奎宁环分子间氢键强度的影响。观察到两种相互作用之间存在强正协同性，结合自由能增加高达16 kJ/mol。通过改变另一个在配合物中既形成分子内氢键又形成分子间氢键的酚羟基上的取代基，可以测量这个中心羟基的性质如何调节与其他两个官能团相互作用之间的协同性。改变这个酚羟基的极性对测量的协同性没有影响。结果表明，氢键网络中的协同性可以理解为两个远程官能团之间的极性相互作用，该相互作用被一个中心官能团减弱。减弱程度由协同性参数κ量化，对于羟基，κ为0.33，它似乎是官能团几何形状或极化率的固有属性，而非极性。
