The photoinitiated proton-coupled electron transfer (PCET) process in photoacid-based adducts is predominantly governed by the evolution of the electron–proton transfer state. However, such a process is underexplored in the case of photobases as the excited states evolve through multiple competitive channels. Here, we elucidate the excited-state dynamics of a photobase, 4-[4′-(dimethylamino)styryl]pyridine (DMASP), in the presence of hexafluoroisopropanol (HFIP) that enables PCET. Transient absorption measurements show the evolution of a protonated species in the excited state with a time constant of ∼2.5 ps. Fluorescence upconversion measurements reveal the signatures of an emissive intramolecular charge transfer state and a protonated state. The role of such states is further confirmed by time-resolved measurements in the presence of trifluoroacetic acid and computational analysis. Furthermore, the proton-abstraction dynamics of DMASP is analyzed in bulk methanol and butanol solvents. The extent of proton abstraction by DMASP is found to be higher in the presence of HFIP when compared with the normal alcohols over a time period of a few picoseconds.

中文翻译：

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光碱 4-[4'(二甲基氨基)苯乙烯基]吡啶中的激发态动力学：光引发质子耦合电子转移的作用

光酸加合物中的光引发质子耦合电子转移（PCET）过程主要受电子-质子转移态演化的控制。然而，在光碱的情况下，由于激发态通过多个竞争通道演化，这一过程尚未得到充分探索。在这里，我们阐明了光碱 4-[4'-(二甲基氨基)苯乙烯基]吡啶 (DMASP) 在六氟异丙醇 (HFIP) 存在下的激发态动力学，该光碱能够实现 PCET。瞬态吸收测量显示激发态质子化物质的演化，时间常数为~2.5 ps。荧光上转换测量揭示了发射性分子内电荷转移态和质子化态的特征。通过在三氟乙酸存在下的时间分辨测量和计算分析进一步证实了这种状态的作用。此外，还分析了 DMASP 在大量甲醇和丁醇溶剂中的质子夺取动力学。发现在几皮秒的时间内，与普通醇相比，在 HFIP 存在下，DMASP 提取质子的程度更高。