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Interactions between a symmetrical tetramethyl-substituted cucurbit[6]uril (host:TMeQ[6]) and 1,ω-alkylenedipyridine (ω = 2,4,6,8,10) dicationic guests were investigated using 1H NMR spectroscopy and single crystal X-ray crystallography. In these inclusion complexes,combined cavity and portal binding in TMeQ[6] were observed,and the length of the bridged alkylene was found to play an important role not only in balancing the overall hydrophilic/hydrophobic interaction between the host and the guest,but also in defining the structure of the resulting inclusion complexes. For the guest 1,2-ethylenedipyridine (Edpy),TMeQ[6] includes a positively charged pyridine ring of Edpy to form an unsymmetrical inclusion complex; for the guest 1,4-butylenedipyridine (Bdpy),TMeQ[6] includes a positively charged pyridine ring of Bdpy,but the different competitive interactions in and between the related inclusion complexes could lead to a fast exchange between the hosts and guests. For the guests with longer bridge chains,such as 1,6-hexamethylenedipyridine (Hdpy) or 1,8-octylenedipyridine (Odpy),a stable pseudorotaxane inclusion complex is formed by combining the hydrophobic cavity and the outer portal dipoleion interactions. However,for 1,10-decatylenedipyridine (Ddpy),the two TMeQ[6] host molecules include the two end pyridine rings of Ddpy and form a dumbbell inclusion complex.
Interactions between a tetramethyl-substituted cucurbit [6] uril (host: TMeQ [6]) and 1, ω- alkylenedipyridine (ω = 2,4,6,8,10) dicationic guests were using 1H NMR spectroscopy and single crystal X ray crystallography. In these inclusion complexes, combined cavity and portal binding in TMeQ [6] were observed, and the length of the bridged alkylene was found to play an important role not only in balancing the overall hydrophilic / hydrophobic interaction between the host for the guest 1,2-ethylenedipyridine (Edpy), TMeQ [6] includes a charged charge ring of Edpy to form an unsymmetrical inclusion complex; for the guest 1,4-butylenedipyridine (Bdpy), TMeQ [6] includes a charged pool of Bdpy, but the different competitive interactions in and between the related inclusion complexes could lead to a fast exchange between the hosts and guests. For the guests withlonger bridge chains, such as 1,6-hexamethylenedipyridine (Hdpy) or 1,8-octylenedipyridine (Odpy), a stable pseudorotaxane inclusion complex formed by combining the hydrophobic cavity and the outer portal dipoleion interactions. However, for 1,10- decatylenedipyridine (Ddpy), the two TMeQ [6] host molecules include the two end pyridine rings of Ddpy and form a dumbbell inclusion complex.