Wortmann Svenja, Kutta Roger Jan, Nuernberger Patrick
Institut für Physikalische und Theoretische Chemie, Universität Regensburg, Regensburg, Germany.
Front Chem. 2022 Sep 28;10:983342. doi: 10.3389/fchem.2022.983342. eCollection 2022.
2,3,5-triphenyltetrazolium chloride (TTC) may convert into phenyl-benzo[c]tetrazolocinnolium chloride (PTC) and 1,3,5-triphenylformazan (TPF) under irradiation with light. The latter reaction, albeit enzymatically rather than photochemically, is used in so-called TTC assays indicating cellular respiration and cell growth. In this paper, we address the photochemistry of TPF with time-resolved spectroscopy on various time scales. TPF is stabilized by an intramolecular hydrogen bond and switches photochemically an E-Z isomerization around an N=N double bond into another TPF-stereoisomer, from which further isomerizations around the C=N double bond of the phenylhydrazone group are possible. We investigate the underlying processes by time-resolved spectroscopy in dependence on excitation wavelength and solvent environment, resolving several intermediates over a temporal range spanning 15 orders of magnitude (hundreds of femtoseconds to hundreds of seconds) along the reaction path. In a quantum-chemical analysis, we identify 16 stable ground-state isomers and discuss which ones are identified in the experimental data. We derive a detailed scheme how these species are thermally and photochemically interconnected and conclude that proton transfer processes are involved.
2,3,5-三苯基氯化四氮唑（TTC）在光照下可能会转化为苯基苯并[c]四氮唑氯（PTC）和1,3,5-三苯基甲臜（TPF）。后一种反应，尽管是酶促反应而非光化学反应，但在所谓的TTC测定中用于指示细胞呼吸和细胞生长。在本文中，我们用时间分辨光谱在不同时间尺度上研究了TPF的光化学。TPF通过分子内氢键稳定，并通过光化学作用在N=N双键周围进行E-Z异构化，转化为另一种TPF立体异构体，在该异构体中，苯腙基团的C=N双键周围还可能发生进一步的异构化。我们通过时间分辨光谱研究了依赖于激发波长和溶剂环境的潜在过程，沿着反应路径在跨越15个数量级（数百飞秒到数百秒）的时间范围内解析了几种中间体。在量子化学分析中，我们确定了16种稳定的基态异构体，并讨论了在实验数据中识别出了哪些异构体。我们推导了一个详细的方案，说明这些物种是如何通过热和光化学相互连接的，并得出结论，质子转移过程参与其中。
