冷叶绿素色素去质子化阴离子的光谱学：一种研究其光合性质的方法

中文摘要 AI 辅助

我们在此介绍一种通过电子光谱研究孤立叶绿素色素的新方法，该方法在9K的冷环境中测量其去质子化阴离子的电子光谱。这些阴离子与相应的中性分子是等电子的，因此它们的电子性质具有可比性。本文通过对比来探讨这一点。通过共振双光子电子脱附光谱，在振动分辨下记录了去质子化脱镁叶绿酸和甲基脱镁叶绿酸Q带的电子光谱，光谱显示出清晰分辨的谱带，延伸至整个可见光谱区，其方式与溶液中相应的中性分子非常相似。结果与通过荧光线窄化光谱（4K）和共振拉曼光谱获得的中性脱镁叶绿素数据进行了比较，发现非常相似。理论分析通过密度泛函（基态DFT WB97XD、杂化交换相关泛函和6-311++G(d,p)基组）和含时密度泛函（TDDFT）计算完成。Q跃迁中活性轨道的比较显示，中性形式和阴离子形式之间具有很大的相似性，同时存在一些轨道及相关能级反转。振动光谱通过Franck-Condon计算进行模拟，以指认电子光谱中的主要跃迁。总体而言，这为叶绿素色素的电子光谱学开辟了一个新的视角。

英文摘要

We introduce here a new approach to the study of isolated chlorophyll pigments with the electronic spectroscopy of their deprotonated anions in a cold environment at 9K. These anions are isoelectronic to the corresponding neutral molecules, therefore their electronic properties are comparable. This comparison is pursued through this article. The electronic spectrum of the Q bands of deprotonated pheophorbide and methyl pheophorbide are recorded by resonant two photon electron detachment with vibrational resolution and show well-resolved bands extending through the visible spectrum in a very similar fashion to their neutral counterparts in solution. The results are compared with data of neutral pheophytin obtained by fluorescence line narrowing spectroscopy at 4K and resonance Raman spectroscopy and found very similar. The theoretical analysis is achieved by density functional (ground state DFT WB97XD, hybrid exchange-correlation functionals and 6-311++G(d,p) basis sets) and time dependent density functional (TDDFT) calculations. The comparison of the active orbitals in the Q transitions shows a great similarity between neutral and anionic forms together with some orbital and related level inversions. The vibronic spectra are simulated by Franck-Condon calculations to assign the dominant transitions of the electronic spectrum. Globally, this is a new perspective in the electronic spectroscopy of chlorophyll pigments that has been opened.

发表机构

• Université Paris-Saclay, CNRS, Institut des Sciences Moléculaires d'Orsay (ISMO)（巴黎萨克雷大学，法国国家科学研究中心，奥赛分子科学研究所）
• Université Paris-Saclay, CEA, CNRS, Institute for Integrative Biology of the Cell (I2BC)（巴黎萨克雷大学，法国原子能和替代能源委员会，法国国家科学研究中心，细胞整合生物学研究所）

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