Lazar Alexandra I, Rohacova Jana, Nau Werner M
Department of Life Sciences and Chemistry, Jacobs University Bremen , Campus Ring 1, 28759 Bremen, Germany.
J Phys Chem B. 2017 Dec 21;121(50):11390-11398. doi: 10.1021/acs.jpcb.7b10651. Epub 2017 Dec 11.
1-Aminopyrene and 1-naphthylamine-5-sulfonic acid were converted to the putrescine (1,4-diaminobutane)-substituted derivatives (dyes 1 and 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 1 and 83 for dye 2). This host-retarded excited-dye deprotonation is a direct consequence of the previously established complexation-induced pK shifts that dyes undergo upon binding to a macrocyclic host. The data set also allows a systematic comparison of complexation-induced pK shifts 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 pK shifts on the size of the macrocycles, we observe for dye 2 that the complexation-induced pK shifts decrease as the portals become larger along the cucurbit[n]uril series.
1-氨基芘和1-萘胺-5-磺酸被转化为腐胺（1,4-二氨基丁烷）取代的衍生物（染料1和染料2）。二氨基丁基锚定基团作为阳离子受体大环化合物（如葫芦[n]脲，n = 6 - 8）和对磺基杯[4]芳烃等的常见结合基团。质子化后，它们在激发态容易发生快速去质子化，从而产生来自未质子化形式的荧光（Förster循环）。通过与阳离子受体大环化合物络合可以抑制去质子化，这使得局部激发（质子化）态的荧光显著增强（染料1增强12倍，染料2增强83倍）。这种主体延迟的激发态染料去质子化是先前确定的染料与大环主体结合时发生的络合诱导的pK位移的直接结果。该数据集还允许对染料基态和激发态中络合诱导的pK位移进行系统比较。趋势具有可比性，这表明结构因素，即主客体络合物的几何形状，决定了位移的大小。关于大环尺寸对绝对pK位移大小的影响，对于染料2，我们观察到随着沿着葫芦[n]脲系列孔口变大，络合诱导的pK位移减小。
