Excited States versus Reaction Intermediates as Active Species in Photoinduced Redox Reactions of Cyrhetrenyl and Ferrocenyl Chalcones: A 351 nm Flash Photolysis Study,The Journal of Physical Chemistry A

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Excited States versus Reaction Intermediates as Active Species in Photoinduced Redox Reactions of Cyrhetrenyl and Ferrocenyl Chalcones: A 351 nm Flash Photolysis Study
The Journal of Physical Chemistry A ( IF 2.7 ) Pub Date : 2019-10-17 , DOI: 10.1021/acs.jpca.9b06603
Tamara Maldonado ₁ , Guillermo Ferraudi , A. Graham Lappin , Fernando Godoy ₁

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The photoinduced redox reactions of two organometallic chalcones: trans, E, (η⁵-C₅H₄C(O)CH═CH-4-benzo-15-crown-5)Re(CO)₃, 1, and trans, E, (η⁵-C₅H₄C(O)CH═CH-4-benzo-15-crown-5)Fe(η⁵-C₅H₄C(O)CH═CH-4-benzo-15-crown-5), 2, were investigated in fluid solution using the flash photolysis technique. For a better understanding of the photoinduced redox processes of these organometallic chalcones, an electron donor, triethylamine (TEA), and an electron acceptor, methylviologen dichloride (MVCl₂), were chosen. Two parallel reaction paths for the decay of the intermediate 1-I, that is, the anion radical of 1, were observed in the presence of TEA. One generates a radical anion, while the other reaction path produces the Z isomer. Instead, the photoinduced reaction of 2 with TEA in MeOH generates an intense absorption band at λ_max = 660 nm, which is attributed to a 2-I·MeOH adduct. The oxidative process between 1-I and MV²⁺ in CH₃CN generates transient spectra consistent with the formation of the radical cation MV^•+. In contrast, the photoinduced reaction between 2 and MV²⁺ showed that the generation of MV^•+ occurs through a complex mechanism. MV^•+ is formed in two steps where the first one is the formation of an adduct between the long-lived metal-to-ligand charge transfer (MLCT)_{Fe→Chalcone} excited state and MV²⁺. These results have shown that intermediates 1-I and 2-I can function as photo-oxidants and photoreductants better than the chalcone short-lived excited states.

中文翻译：

激发态对反应中间体作为环丙二烯和二茂铁基查尔酮的光致氧化还原反应中的活性物种：351 nm闪光光解研究

2种有机金属查耳酮的光致氧化还原反应：反式，ê，（η ⁵ -C ₅ H ^ ₄ C（O）CH = CH-4-苯并-15-冠-5）的Re（CO）₃，1，和反式，ë，（η ⁵ -C ₅ H ^ ₄ C（O）CH = CH-4-苯并-15-冠-5）的Fe（η ⁵ -C ₅ H ^ ₄ C（O）CH = CH-4-苯并-15- -cro-5），2使用快速光解技术在液体溶液中进行了研究。为了更好地理解这些有机金属查耳酮的光诱导氧化还原过程，选择了一个电子给体三乙胺（TEA）和一个电子受体甲基紫罗兰二氯化物（MVCl ₂）。在存在TEA的情况下，观察到了两条平行的反应路线，用于降解中间体1-I（即1的阴离子自由基）。一个产生自由基阴离子，而另一个反应路径产生Z异构体。相反，2与TEA在MeOH中的光诱导反应在_λmax = 660 nm处产生强烈的吸收带，这归因于2-I·MeOH加合物。CH ₃ CN中1-I与MV ²⁺之间的氧化过程产生与自由基阳离子MV ^•+形成一致的瞬态光谱。相反，2和MV ²⁺之间的光诱导反应表明MV ^•+的产生是通过复杂的机制发生的。MV ^•+分两步形成，第一步是在长寿命的金属到配体电荷转移（MLCT）_{Fe→查耳酮}激发态与MV ²⁺之间形成加合物。这些结果表明，中间体1 - I和2-我可以作为查尔酮短寿命激发态的光氧化剂和光还原剂。

更新日期：2019-10-17

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