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。基于这类系统固有的双发射，我们最近开发了一种底物，它根据两种不同酶的两个正交裂解位点显示多达四种发射颜色。虽然酶转化在现实条件下代表着不可逆的转换，但我们希望将这个由不同发射颜色编码的正交反应的概念转化为可逆反应，并希望将其与非正交结合位点的行为进行比较。第二个体系由光酸中心和光碱性部分组成，分别用核磁共振光谱和荧光相关光谱研究了可逆键的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上的结合的影响程度。路易斯碱与含硼取代的羟基芘类化合物的可逆结合有望成为正交结合部位。羧化的羟基芘衍生物在一个分子内结合了光酸性和-碱性。作为光碱的公认的羧酸盐被亚胺碱所补充；后者的化合物最近被描述为所谓的超光碱的一部分。由于酸的有序性预计会在激发时发生变化，因此可以探索通过氢键网络从羟基部分到碱性位置的ESPT。计划利用这一特征来研究不同溶剂组成中的氢键链。因此，这项赠款提案的一个主要目标是制备各种数量和溶解性的区域异构体，以适应各种光谱方法的需要。

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.