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首页> 外文期刊>The journal of physical chemistry, A. Molecules, spectroscopy, kinetics, environment, & general theory >Electron Transfer from Triethylamine to the Triplet State of Dinitronaphthalenes, 4,4'-Dinitrobiphenyl and 2,7-Dinitrofluorenone: Time Resolved UV-Vis Spectroscopic and Conductometric Study in Polar Solvents
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Electron Transfer from Triethylamine to the Triplet State of Dinitronaphthalenes, 4,4'-Dinitrobiphenyl and 2,7-Dinitrofluorenone: Time Resolved UV-Vis Spectroscopic and Conductometric Study in Polar Solvents

机译：电子从三乙胺转移到二硝基萘，4,4'-二硝基联苯和2,7-二硝基芴酮的三重态：极性溶剂中的时间分辨紫外可见光谱和电导率研究

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摘要

The photoreduction of 1,3-, 1,4-, 1,5-, 1,8-, and 2,3-dinitronaphthalene (DNN) as well as of 4,4'-dinitrobiphenyl and 2,7-dinitrofluorenone by 1,4-diazabicyclo[2.2.2]octane (DABCO), triethylamine (TEA), and diethylamine (DEA) in argon-saturated acetonitrile and mixtures with water was studied by spectroscopic and conductometric means after nanosecond 354 nm pulses. The rate constant for quenching of the triplet state of the dinitroarenes by TEA is k_q ≈ 1.6 * 10~(10) M~(-1) s~(-1) in acetonitrile and markedly smaller on an addition of water. The secondary transients with maxima at 380-550 nm in the presence of TEA or DEA at concentrations of <1 mM and of DABCO are ascribed to radical anions of the dinitroarenes, formed via photoinduced electron transfer to the triplet state. With TEA at higher concentrations, in addition a delayed radical formation, involving the α-aminoethyl radical as precursor, was observed throughout. The radicals subsequently undergo a termination reaction yielding the corresponding nitroso compounds as major primary products; the process is substantially slowed in the presence of water (≤5 M). For 1,4-DNN a longer lived intermediate is formed. It is attributed to the dianion, which is also observable in alkaline 2-propanol. The two photoinduced reduction reactions of the dinitroarenes by TEA and the subsequent radical disproportionation are supported by time-resolved conductometric measurements. The conductivity signals have generally a much longer half-life than the absorbing intermediates. The mechanism and the effects of substitution and concentrations of TEA, oxygen, and water are discussed.
机译：1、3-，1,4-，1,5-，1,8-和2,3-二硝基萘（DNN）以及4,4'-二硝基联苯和2,7-二硝基芴酮的光还原在纳秒354 nm脉冲后，通过光谱和电导方法研究了在氩气饱和的乙腈中与水形成的混合物中的1,4-二氮杂双环[2.2.2]辛烷（DABCO），三乙胺（TEA）和二乙胺（DEA）。 TEA淬灭二硝基芳烃三重态的速率常数为k_q≈1.6 * 10〜（10）M〜（-1）s〜（-1），加入水后明显减小。在浓度小于1 mM的TEA或DEA和DABCO存在下，在380-550 nm处具有最大值的次级瞬变归因于二硝基芳烃的自由基阴离子，该自由基是通过光诱导电子转移到三重态形成的。整个过程中，使用较高浓度的TEA，还观察到了延迟的自由基形成，其中涉及α-氨基乙基自由基作为前体。自由基随后进行终止反应，生成相应的亚硝基化合物作为主要主要产物;在水（≤5M）存在的情况下，该过程会大大减慢速度。对于1,4-DNN，形成了寿命更长的中间体。它归因于二价阴离子，在碱性2-丙醇中也可观察到。时间分辨电导率测量支持了TEA引起的二硝基芳烃的两次光诱导还原反应和随后的自由基歧化。电导率信号通常具有比吸收中间体更长的半衰期。讨论了机理以及TEA，氧气和水的取代和浓度的影响。

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