Romanov Ivan, Boeije Yorrick, Toldo Josene M, Do Casal Marianna T, Barbatti Mario, Buma Wybren Jan
Van't Hoff Institute for Molecular Sciences, University of Amsterdam, Science Park 904, Amsterdam 1098 XH, the Netherlands.
Department of Chemical Engineering and Biotechnology, University of Cambridge, Philippa Fawcett Drive, Cambridge CB3 0AS, U.K.
J Phys Chem A. 2025 Jan 9;129(1):36-49. doi: 10.1021/acs.jpca.4c05792. Epub 2024 Dec 17.
The spectroscopic and dynamic properties of methyl ferulate─a naturally occurring ultraviolet-protecting filter─and microsolvated methyl ferulate have been studied under molecular beam conditions using resonance-enhanced multiphoton ionization spectroscopy in combination with quantum chemical calculations. We demonstrate and rationalize how the phenyl substitution pattern affects the state ordering of the lower excited singlet state manifold and what the underlying reason is for the conformation-dependent Franck-Condon (FC) activity in the UV-excitation spectra. Studies on microsolvated methyl ferulate reveal potential coordination sites and the influence of such coordination on the spectroscopic properties. Our quantum chemical studies also enable us to obtain a quantitative understanding of the dominant excited-state decay routes of the photoexcited ππ* state involving a ∼3 ns intersystem crossing pathway to the triplet manifold─which is much slower than found for coumarates─and a relatively fast intersystem crossing back to the ground state (∼30 ns). We show that a common / crossing can very well explain the observation that lifetimes are quasi-independent of the phenyl substitution pattern.
在分子束条件下，结合量子化学计算，利用共振增强多光子电离光谱研究了阿魏酸甲酯（一种天然存在的紫外线防护滤光剂）和微溶剂化阿魏酸甲酯的光谱和动力学性质。我们证明并解释了苯基取代模式如何影响较低激发单重态流形的态序，以及紫外激发光谱中构象依赖性弗兰克 - 康登（FC）活性的潜在原因。对微溶剂化阿魏酸甲酯的研究揭示了潜在的配位位点以及这种配位对光谱性质的影响。我们的量子化学研究还使我们能够定量理解光激发ππ*态的主要激发态衰变途径，包括一条约3 ns的系间窜越途径至三重态流形（这比香豆酸盐的情况慢得多）以及一条相对较快的系间窜越回到基态（约30 ns）。我们表明，一个共同的/交叉的情况能够很好地解释寿命与苯基取代模式几乎无关这一观察结果。
