Bifunctional Photoacids with Multicolour Emission

在激发态质子转移（ESPT）反应中发现了荧光光谱和光化学的独特结合。基于这类体系的固有双发射特性，我们最近开发了一种底物，它在两种不同酶的两个正交切割位点的依赖下显示多达四种发射颜色。虽然酶转化在现实条件下代表不可逆转化，但我们希望将这种有前途的正交反应性概念（由不同的发射颜色编码）转移到可逆反应中，并将其与非正交结合位点的行为进行比较。后一体系由光酸性位点与光碱性部分结合而成。用核磁共振光谱和荧光相关光谱分别探讨了可逆键形成和解离的热力学和动力学。这些测量可以量化一个位点上的结合对另一个位点的结合的影响程度。lewis碱与硼取代羟基芘衍生物的可逆结合有望作为正交结合位点。羧基化的羟基芘衍生物在一个分子内结合了光酸性和-碱性。已建立的羧酸盐作为光碱由亚胺碱补充；后一种化合物最近被描述为所谓的超级光碱的一部分。由于预期酸的顺序在激发后会发生变化，因此可以通过氢键网络探测从羟基部分到碱性位点的ESPT。计划利用这一特性来研究各种溶剂组成中的氢键链。因此，这项拨款提案的一个主要目标是制备数量和溶解度适合各种光谱方法需要的各种区域异构体。

The unique combination of fluorescence spectroscopy and photochemistry is found in the excited-state proton transfer (ESPT) reaction. Based on the intrinsic dual emission of suchlike systems, we recently developed a substrate which shows up to four emission colors in dependence of two orthogonal cleavage sites for two different enzymes. While the enzymatic conversions represent irreversible transformations under realistic conditions, we would like to transfer this promising concept of orthogonal reactivities, encoded by different emission colors, to reversible reactions and would like to compare it to the behavior of non-orthogonal binding sites. The latter system is represented by the photoacidic site, combined with a photobasic moiety.Thermodynamics and kinetics of reversible bond formation and dissociation are probed by NMR-spectroscopy and fluorescence correlation spectroscopy, respectively. These measurements allow for quantifying the extent by which binding on one site influence the binding at the other site. The reversible binding of Lewis-bases to Boron-substituted hydroxypyrene derivatives is expected to act as the orthogonal binding sites. The carboxylated hydroxypyrene derivatives combine photoacidity and -basicity within one molecule. The well-established carboxylate as photobase is complemented by an imine base; this latter compound was recently described as part of a so-called super-photobase. As the ordering of acidities is expected to change upon excitation, ESPT from the hydroxyl-moiety to the basic site via a hydrogen-bonding network can be probed. It is planned to exploit this feature in studying hydrogen-bonding chains in various solvent compositions. Therefore, one major objective of this grant proposal is the preparation of various regioisomers in amounts and solubility which fit to the needs of the various spectroscopy methods.