Analytical Applications of Excited-state proton transfer (ESPT) in Pyrene-Based Photoacids

质子转移作为最基本的反应之一，已经被深入研究了60多年。我们最近在著名的光酸pyranine（8-羟基芘-1,3,6-三磺酸盐）的基础上发表了一系列的光酸，它们在激发态下的pka值低至-4。然而，除了用于研究反应动力学之外，还可以预见这些光酸的更多应用。质子按需，即通过可见超短激光脉冲激发，可以触发反应级联，如酮-烯醇重排，然后可以通过时间分辨红外光谱进行研究。当分子停留在激发态数纳秒时，观察到双发射。在质子转移之前，光酸的激发态寿命仅持续皮秒，允许通过Förster-resonance超灵敏度能量转移在较低纳米范围内进行距离测量。当更多（照片）化学活性的侧基附着在芘核上时，可以产生更多的发射态。预期的应用是经受住了过去实现的想法，因为所有三个磺酸侧基同时转化为更强的吸电子基团。我们提出了两种方法来克服目前的限制：一方面，作为起始材料的芘将被氮杂芘取代，并从中提取出更强的光酸。这些衍生品将引起两个合作伙伴的极大兴趣。另一方面，我们引入了辅助取代，通过x射线晶体学验证，这使我们能够选择性地修饰芘核心区域。拨款提案的核心是致力于这些化合物的合成，我们希望从这些化合物中保持我们以前羟基芘衍生物的有益特性，即高荧光量子产率，高光稳定性和电磁波谱可见范围内的电子跃迁。

Proton-transfer as one of the most fundamental reactions is intensively studied for more than 60 years. We recently published a series of photoacids on the basis of the well-known photoacid pyranine (8-Hydroxypyrene-1,3,6-trisulfonate) which exhibit pKA-values in the excited-state down to -4. However, more applications of these photoacids can be foreseen beyond their use for studying reaction dynamics. Protons-on-demand, i.e. by excitation with visible ultrashort laser-pulses, can trigger reaction cascades like keto-enol rearrangements which can then be studied e.g. by time-resolved IR spectroscopy. As the molecules stay in the excited-state for several nanoseconds, dual emission is observed. The lifetime in the excited-state of the photoacid before the proton-transfer, only lasting for picoseconds, allows for distance measurement in the lower nanometer range by Förster-resonance energy transfer with ultrasensitivity. More emissive states can be created when more (photo)chemically active side groups are attached to the pyrene core.The anticipated applications are yet ideas which withstood realization in the past as all three sulfonate side groups were simultaneously transformed to stronger electron-withdrawing moieties. We propose two approaches to overcome the current limitations: on the one hand, pyrene as starting material will be replaced by aza-pyrene from which even stronger photoacids are figured out. These derivatives would be of great interest for two collaboration partners. On the other hand, we introduced helper substitution, verified by x-ray crystallography, which enables us to modify the pyrene core regioselectively. The marrow of the grant proposal is dedicated to the synthesis of these compounds from which we expect maintenance of the beneficial properties of our previous hydroxy-pyrene derivatives, i.e. high fluorescence quantum yields, high photostabilities and electronic transitions in the visible range of the electromagnetic spectrum.