Studies of Highly Reactive Biradical and Cation Radicals

高反应性双自由基和阳离子自由基的研究

• 批准号: 06044014
• 负责人: MIYASHI Tsutomu
• 金额: $ 3.39万
• 依托单位: Tohoku University
• 依托单位国家: 日本
• 项目类别: Grant-in-Aid for international Scientific Research
• 财政年份: 1994
• 资助国家: 日本
• 起止时间: 1994 至 1995
• 项目状态: 已结题
• 来源: https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-06044014/
• 关键词: Biradical; Cation Radical; Back Electron Transfer; Organic Photochemistry; Photoinduced Electron Transfer; Reaction Mechanism; Laser Flash Photolysis; Photoacousic Calorimetry; Solid State; 光音響法

We have studied the relationship between biradical (BR) and cation radical(CR)intermediates in the photoinduced electron-tranfer(PET)skeletal rearrangement of organic compounds. In general, a nondistonic CR of a donor substrate generated by PET from the excited state of sensitizer (A)can undergo the bond formation or bond cleavage to give a more stable distonic CR intermediates (I^<・+>). Although free distonic CRs have been often observed spectroscopically and/or captured by a trapping reagent such as molecular oxygen or alcohol, reactions of a distonic CR in an ion pair [I^<・+>/A^<・->] have not been well understood yet. There are two possibilities for the decay of a distonic CR intermediate. One is back electron transfer (BET) from A^<・-> to give a singlet or triplet BR intermediate, which give final product (s) by the bond cleavage or formation. The other one is an alternative possible sequence, i.e., bond cleavage or formation in a CR stage followed by BET.In order to know which pro … More cess is operative, we use two complementary laser techniques, time-resolved absorption spectroscopy for the direct observation of CR and BR intermediates and time-resolved photoacoustic calorimetry for the determination of energy of [I^<・+>/A^<・->]. As result, we found three PET reactions that proceed through both CR and BR intermediates. The first is the PET degenerate Cope rearrangement of 2,5-diaryl-1,5-hexadiene, which proceeds in a CR cyclization-BR cleavage mechanism through 1,4-diarylcyclohexa-1,4-diyl CR and 1,4-diarylcyclohexa-1,4-diyl BR.The second example is the degenerate methylenecyclopropane rearrangement of 2,2-diarylmethylenecyclopropane induced by PET,which involves a trimethlenemethane CR (TMM^<・+>) and corresponding BR (TMM). The last case is the generation of singlet and triplet tetramethyleneethane BRs by cyclization of 5,5-dimethy1-2,3-bis (1-phenylvinyl) cyclopentadiene CR.Those three PET reactions provided an intriguing conclusion that BET in an ion pair is an important key process which connects CR chemistry with BR chemistry. This conclusion is quite noteworthy since, up to the present, BET was usually considered as an energy wasting process. Less

我们研究了有机化合物光致电子转移（PET）骨架重排中双自由基（BR）和阳离子自由基（CR）中间体之间的关系。一般来说，由PET从敏化剂(A)的激发态产生的供体底物的非二等式CR可以经历成键或键断裂，从而得到更稳定的二等式CR中间体(I^<·+>)。尽管游离的双张 CR 经常通过光谱观察和/或通过捕获试剂（例如分子氧或酒精）捕获，但离子对 [I^<·+>/A^<·->] 中双张 CR 的反应尚未得到很好的理解。等渗 CR 中间体的衰变有两种可能性。一种是从A^<·->进行反电子转移（BET）以得到单线态或三线态BR中间体，其通过键断裂或形成而得到最终产物。另一种是另一种可能的顺序，即在 CR 阶段中键断裂或形成，然后进行 BET。为了了解哪个过程是有效的，我们使用两种互补的激光技术，即用于直接观察 CR 和 BR 中间体的时间分辨吸收光谱和用于测定 CR 和 BR 中间体能量的时间分辨光声量热法。 [I^<·+>/A^<·->]。结果，我们发现了三个 PET 反应同时通过 CR 和 BR 中间体进行。第一个是2,5-二芳基-1,5-己二烯的PET简并Cope重排，通过1,4-二芳基环六-1,4-二基CR和1,4-二芳基环六-1,4-二基BR以CR环化-BR裂解机制进行。第二个例子是简并亚甲基环丙烷重排 由PET诱导的2,2-二芳基亚甲基环丙烷，涉及三亚甲基CR(TMM^<·+>)和相应的BR(TMM)。最后一个案例是通过 5,5-二甲基 1-2,3-双（1-苯基乙烯基）环戊二烯 CR 环化生成单线态和三线态四亚甲基乙烷 BR。这三个 PET 反应提供了一个有趣的结论：离子对中的 BET 是将 CR 化学与 BR 化学联系起来的重要关键过程。这个结论非常值得注意，因为到目前为止，BET 通常被认为是一个能源浪费过程。较少的

项目成果

Yasutake Takahashi: "Cycloreversion of arene endoperoxides induced by electron transfer." J.Chem.Soc.,Chem.Commun.---. 13-14 (1994)

Yasutake Takahashi：“电子转移诱导芳烃内过氧化物环化。”

Takanori Suzuki: "An absolute asymmetric synthesis of the [2+2] cycloadduct via single crystal-to-single crystal transformation by charge-transfer excitation of solid-state molecular complexes composed of arylolefins and bis [1,2,5] thiadiazolotetracyanoq

Takanori Suzuki：“通过由芳基烯烃和双[1,2,5]噻二唑四氰基组成的固态分子复合物的电荷转移激发，通过单晶到单晶的转变，绝对不对称合成[2 2]环加合物”

Seock Kyu Khim: "A novel method for synthesis of functionalized piperidines." Tetrahedron Lett.35. 999-1002 (1994)

Seock Kyu Khim：“一种合成功能化哌啶的新方法。”

Lev R.Ryzhkov: "Low-Temperature Reactions in Single Crystals of Two Polymorphs of the Polycyclic Nitramine 15N-HNIW." J.Phys.Chem.100. 163-169 (1996)

Lev R.Ryzhkov：“多环硝胺 15N-HNIW 两种多晶型物的单晶中的低温反应”。

Kimio Akiyama: "Spin Polarization Conservation during Intramolecular Triplet-Triplet Energy Transfer Studied by Time-Resolved EPR Spectroscopy." J.Am. Chem. Soc.116. 5324-5327 (1994)

Kimio Akiyama：“通过时间分辨 EPR 光谱研究分子内三重态-三重态能量转移过程中的自旋极化守恒。”