Host-guest complexes of a water soluble cucurbit[6]uril derivative with some dications of 1,ω-alkyldipyridines: 1H NMR and X-ray structures

Abstract

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 1 H 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 dipole-ion 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.symmetrical tetramethyl-substituted cucurbit[6]uril, 1,ω-alkylenedipyridine (ω = 2, 4, 6, 8, 10) dicationic guests, host-guest complex, 1 H NMR spectroscopy, single crystal X-ray crystallography

A new cryptand/paraquat [2]pseudorotaxane

“…Crown ethers [7][8][9][10][11][12][13], cryptands [14][15][16][17][18], cyclodextrins [19][20][21][22], cucurbit[n]urils [23][24][25], and calix[n]arenes [26,27] have been universally used as hosts to fabricate various supramolecular assemblies, which have great potential in molecular devices, chemosensors, and nano materials. Paraquat ( Figure 1) and its derivatives (N,N′-dialkyl-4,4′-bipyridinium salts) are common guests in the field of pseudorotaxanes and rotaxanes [28][29][30][31].…”

Tripod molecules build molecular networks and open-dimer capsules by weak interactions

“…Crystal engineering has the ability to control molecular organization in the solid state, leading to materials with novel structures and functions [1][2][3][4][5]. A current concern is to use molecules with geometrically well-defined cores and multiple peripheral sites that interact intermolecularly to engineer molecular crystals [6].…”