Radiochromism of spiropyran via the radical ions studied by pulsed electron radiolysis and DFT calculation

IF 2.8 3区物理与天体物理 Q3 CHEMISTRY, PHYSICAL

Radiation Physics and Chemistry Pub Date : 2024-11-13 DOI:10.1016/j.radphyschem.2024.112393

Minoru Yamaji , Yasuko Osakada , Sachiko Tojo , Mamoru Fujitsuka

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Abstract

Spiropyrans and spirooxazines (SP) are known to undergo photochromism to form merocyanines (MC). In this study, upon pulsed electron radiolysis of SP in organic solvents, we observed the transient absorption spectra of SP radical ions in the visible wavelength region. Based on first-order kinetics in the microsecond time domain, the absorption spectra changed to different ones, which were plausibly due to the radical ions of the corresponding MC. The reaction rates from SP radical ions to MC ones were determined. Using heats of formation for the radical ions of SP and MC evaluated with DFT calculations, the differences in heats of formation between the radical ions of SP and MC were determined to be exothermic. The reaction rate correlated with the difference in heat of formation, which depended on the parity of the radical ions. Time-dependent DFT calculations provided the SOMO surfaces of the radical ions of SP and MC. Comparing the SOMO with the LUMO, HOMO, and HOMO-1 surfaces of the neutral SP, we found that the attached electron locates on the LUMO upon one-electron reduction in SP, whereas the HOMO-1 of SP is involved in one-electron oxidation of SP rather than the HOMO.

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通过脉冲电子辐射分解和 DFT 计算研究螺吡喃通过自由基离子产生的放射性变色作用

众所周知，螺吡喃和螺恶嗪（SP）可通过光致变色作用形成美拉德嗪（MC）。在本研究中，我们在有机溶剂中对 SP 进行脉冲电子辐射分解时，观察到了 SP 自由基离子在可见光波段的瞬态吸收光谱。根据微秒时域的一阶动力学，吸收光谱发生了变化，可能是由于相应 MC 的自由基离子引起的。测定了从 SP 自由基离子到 MC 自由基离子的反应速率。利用 DFT 计算评估了 SP 和 MC 自由基离子的形成热，确定 SP 和 MC 自由基离子之间的形成热差异为放热反应。反应速率与形成热的差异相关，而形成热的差异取决于自由基离子的奇偶性。随时间变化的 DFT 计算提供了 SP 和 MC 自由基离子的 SOMO 表面。将 SOMO 与中性 SP 的 LUMO、HOMO 和 HOMO-1 表面进行比较，我们发现在 SP 的单电子还原反应中，附着电子位于 LUMO，而在 SP 的单电子氧化反应中，SP 的 HOMO-1 而不是 HOMO 参与了反应。

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来源期刊

Radiation Physics and Chemistry 化学-核科学技术

CiteScore

5.60

自引率

17.20%

发文量

574

审稿时长

12 weeks

期刊介绍： Radiation Physics and Chemistry is a multidisciplinary journal that provides a medium for publication of substantial and original papers, reviews, and short communications which focus on research and developments involving ionizing radiation in radiation physics, radiation chemistry and radiation processing. The journal aims to publish papers with significance to an international audience, containing substantial novelty and scientific impact. The Editors reserve the rights to reject, with or without external review, papers that do not meet these criteria. This could include papers that are very similar to previous publications, only with changed target substrates, employed materials, analyzed sites and experimental methods, report results without presenting new insights and/or hypothesis testing, or do not focus on the radiation effects.