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Sym-bis(benzimidazole)-2,2’-ethylene cations act as a new axle template for threading cucurbit[6]uril derivatives on,forming[2]pseudorotaxane and[3]pseudorotaxane.These new complexes have been studied using ~1 H NMR,UV-vis absorption spectroscopy and X-ray analysis.Changes in the ~1 H NMR spectra indicate that the two types of pseudorotaxane can be formed by varying the host concentration. UV-vis absorption titration experiments at different pH values demonstrate that interesting pK_a shifts of the bis-benzimidazole derivatives can be induced by the host-guest complexation.The associated constants were calculated to be 2.81×10~4 L/mol and 9.06×10~6 L/mol for the[2]pseudorotaxanes and |3]pseudorotaxanes,respectively.Furthermore,X-ray diffraction studies of the solid state structures provide unequivocal proof of the host concentration dependent pseudorotaxane,which is strongly in line with the evidences in solution.
Sym-bis (benzimidazole) -2,2’-ethylene cations act as a new axle template for threading cucurbit [6] uril derivatives on, forming [2] pseudorotaxane and [3] pseudorotaxane.These new complexes have been studied using ~ 1 H NMR, UV-vis absorption spectroscopy and X-ray analysis. Change in the ~ 1 H NMR spectra indicate that the two types of pseudorotaxane can be formed by varying the host concentration. UV-vis absorption titration experiments at different pH values demonstrate that interesting pK_a shifts of the bis-benzimidazole derivatives can be induced by the host-guest complex. The associated constants were calculated to be 2.81 × 10 -4 L / mol and 9.06 × 10 -6 L / mol for the [2] pseudorotaxanes and | 3] pseudorotaxanes, respectively.Furthermore, X-ray diffraction studies of the solid state structures provide unequivocal proof of the host concentration dependent pseudorotaxane, which is strongly in line with the evidences in solution.