The steric hindrance controlled [2]pseudorotaxanes constructed by V-type stilbene dyes⊂CB[7]

In this paper, five V-type stilbene dyes (VD, 1a-1e) that had unchanged dimethylamino phenylethenyl (DMPE) arm as inclusive location with CB[7] and another arm with different steric hindrance aryloxyethyl (AE) group were designed and synthesized. Their inclusive characteristics and stability to CB[7] were studied. Fluorescence spectroscopy and ¹H NMR method were used respectively to study the inclusive characteristics of 1a⊂CB[7], 1b⊂CB[7], 1c⊂CB [7], 1d⊂CB[7] and 1e⊂CB[7]. Fitting curves results of fluorescent titration indicated that 1:1 complexes between CB[7] and VD were constructed, and their inclusive constants were calculated respectively. The order of inclusive constants K_1a⊂CB[7]> K_1b⊂CB[7]> K_1c⊂CB[7] > K_1d⊂CB[7] was consistent with the magnitude of the steric hindrance, however, 1e did not include with CB[7]. Therefore, a series of steric hindrance controlled [2]pseudorotaxanes were constructed.