| Abstrakt: |
1-Aminopyrene and 1-naphthylamine-5-sulfonic acid were converted to the putrescine (1,4-diaminobutane)-substituted derivatives (dyes 1and 2). The diaminobutyl anchor serves as a common binding motive for cation-receptor macrocycles such as cucurbit[n]urils (n= 6–8) and p-sulfonatocalix[4]arene. When protonated, they are prone to undergo a rapid deprotonation in their excited state to result in fluorescence from the unprotonated form (Förster cycle). The deprotonation can be suppressed by complexation with cation-receptor macrocycles, which allows the fluorescence of the locally excited (protonated) state to be dramatically enhanced (factor 12 for dye 1and 83 for dye 2). This host-retarded excited-dye deprotonation is a direct consequence of the previously established complexation-induced pKashifts that dyes undergo upon binding to a macrocyclic host. The data set also allows a systematic comparison of complexation-induced pKashifts in the ground and excited state of a dye. The trends are comparable, which suggests that structural factors, that is, the geometry of the host–guest complexes, determine the magnitude of the shifts. In regard to the magnitude of the absolute pKashifts on the size of the macrocycles, we observe for dye 2that the complexation-induced pKashifts decrease as the portals become larger along the cucurbit[n]uril series. |
