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首页> 外文期刊>The journal of physical chemistry, A. Molecules, spectroscopy, kinetics, environment, & general theory >Electronic properties of N(5)-ethyl flavinium ion
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Electronic properties of N(5)-ethyl flavinium ion

机译：N（5）-乙基黄酮离子的电子性质

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摘要

We investigated the electronic properties of N(5)-ethyl flavinium perchlorate (Et-Fl~+) and compared them to those of its parent compound, 3-methyllumiflavin (Fl). Absorption and fluorescence spectra of Fl and Et-Fl~+ exhibit similar spectral features, but the absorption energy of Et-Fl~+ is substantially lower than that of Fl. We calculated the absorption signatures of Fl and Et-Fl~+ using time-dependent density functional theory (TD-DFT) methods and found that the main absorption bands of Fl and Et-Fl~+ are (π,π*) transitions for the S _1 and S_3 excited states. Furthermore, calculations predict that the S_2 state has (n,π*) character. Using cyclic voltammetry and a simplistic consideration of the orbital energies, we compared the HOMO/LUMO energies of Fl and Et-Fl~+. We found that both HOMO and LUMO orbitals of Et-Fl~+ are stabilized relative to those in Fl, although the stabilization of the LUMO level was more pronounced. Visible and mid-IR pump-probe experiments demonstrate that Et-Fl~+ exhibits a shorter excited-state lifetime (590 ps) relative to that of Fl (several nanoseconds), possibly due to faster thermal deactivation in Et-Fl~+, as dictated by the energy gap law. Furthermore, we observed a fast (23-30 ps) S_2 → S_0 internal conversion in transient absorption spectra of both Fl and Et-Fl~+ in experiments that utilized pump excitations with higher energy.
机译：我们研究了N（5）-乙基高氯酸黄酮（Et-Fl +）的电子性质，并将其与其母体化合物3-甲基鲁米黄素（Fl）进行了比较。 Fl和Et-Fl〜+的吸收光谱和荧光光谱表现出相似的光谱特征，但是Et-Fl〜+的吸收能明显低于Fl。我们使用时变密度泛函理论（TD-DFT）方法计算了Fl和Et-Fl〜+的吸收特征，发现Fl和Et-Fl〜+的主要吸收带为（π，π*）跃迁S _1和S_3激发态。此外，计算预测S_2状态具有（n，π*）特征。使用循环伏安法和对轨道能量的简单考虑，我们比较了Fl和Et-Fl〜+的HOMO / LUMO能量。我们发现Et-F1 +的HOMO和LUMO轨道相对于F1中的那些都是稳定的，尽管LUMO能级的稳定更为明显。可见和中红外泵浦探针实验表明，相对于Fl（几纳秒），Et-Fl〜+具有较短的激发态寿命（590 ps），这可能是由于Et-Fl〜+的热失活更快，根据能隙定律。此外，在利用较高能量的泵浦激发的实验中，我们在Fl和Et-Fl〜+的瞬态吸收光谱中观察到了快速（23-30 ps）S_2→S_0内部转换。

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