The Mechanism And Application Of The Cooperativity Of Intermolecular Forces Between Cucurbit[n]uril And Guest Molecules

The relationship of intermolecular forces, including their additivity, cooperativityand directivity, is one of the key scientific problems in supramolecular chemistry.Cucurbit[n]uril (CB[n]) is a kind of cyclic host with two multi-carbonyl ports and ahydrophobic cavity. CB[n] can strongly attract molecules with positively chargedgroups and hydrophobic groups though charge-dipole interaction, hydrogen bond, andhydrophobic interactions. The characteristics of CB[n] afford its important applicationvalue in chemistry relating tomaterial science,environmental science, and life science.Thus, research of molecular recognition mechanisms and relationship of theintermolecular forces in CB[n]-guest systems is valuable and helpful for furtherunderstanding the self-assembly systems, and also for designing new functionalself-assembly systems, developing new assemble methods and expanding theapplications of CB[n]. In this thesis,1H NMR spectroscopy,calorimetry,quantumchemicalcomputingand molecular dynamic simulation have been employed toinvestigate the cooperativity of intermolecular forces between CB[n] and selected guestmolecules, and to study the impact of the cooperativity on the binding thermodynamicsand the exchange model (fast or slow exchange) between bound and free guestmolecules based on the time scale of NMR.We investigated the cooperativity of charge-dipole interaction, hydrogen bondingand hydrophobic interaction in the systems of CB[7] and cyclohexyl guests, andclarified the mechanism of slow and fast exchange for the first time based on thecooperativity and mismatch between intermolecular forces. We pointed out that it is thecooperativity or mismatch of the three intermolecular interactions that determines theenergy barrier of bound guest molecules getting out of the cavity of CB[7], which inturn determines the exchange rate between the bound and free guest molecules, andaffects the binding constant though changing the binding enthalpy and entropy. Thehydrogen bonds between the carbonyls of CB[7] and hydrogens of pyridyl andimidazolyl cations were investigated though NMR and quantum chemicalcomputing.We found the cooperativity or mismatch of hydrogen bonds and hydrophobic interaction in imidazolyl cations or in pyridyl cations systems and explained theireffects on the binding thermodynamics.Based on the mechanism study on the cooperativity of intermolecular forces, wedesigned the high selective recognition system of CB[7] and hexadecyl dimethyl benzylammonium chloride (HDBAC) with cooperative charge-dipole and hydrophobicinteractions. Various self-assembly structures were observed. Transformationfrommicelles to nanorods and then to nanosheets in this system was achieved by carefultuning the HDBAC/CB[7] molar ratio. Areasonable transformation mechanism was alsoproposed. Furthermore, by taking advantage of the cooperativity of multi-hydrogenbonds, we designed and successfully grew a multi-channel crystal based on CB[6] andhexacyclen.