Formation and Reaction Kinetics of Biradicals and Triplet States in a Series of Carboxylated 1,4,5,8-Naphthalene Diimides
Formation and Reaction Kinetics of Biradicals and Triplet States in a Series of Carboxylated 1,4,5,8-Naphthalene Diimides
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一系列羧基化 1,4,5,8-萘二酰亚胺中双自由基和三重态的形成和反应动力学
DOI：
10.1021/acs.jpca.0c06639
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发表时间：
2020
期刊：
影响因子：
--
通讯作者：
Kelly, Lisa A.
中科院分区：
文献类型：
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作者：
Sova, Stacey;Kelly, Lisa A.
采用荧光光谱、磷光光谱和纳秒激光闪光光解技术对一系列羧酸烷基取代的1,4,5,8-萘二亚胺（NDI）化合物的单重态失活产物进行了表征。反应中间体被量化为烷基连接体中亚甲基数量的函数。光致电子转移（PET）到单重态激发态的速率常数从1.2 × 1010s-1变化到4.9 × 1010s-1。在含有4 ~ 1个亚甲基的化合物中，长寿命的氨基酮基自由基的产率在15% ~ 60%之间。在具有最慢PET的化合物的直接激发下观察到主要的三重态。该t11态被DABCO电子给体还原猝灭。氨基酮基自由基对电子给体无反应，但与氢原子给体β-巯基乙醇反应。该化合物包括一类新型的长波长和强吸收紫外线激活的发色团，在没有共敏剂的情况下，通过直接355nm激发产生碳中心双自由基。
The singlet-state deactivation products in a series of alkyl carboxylate substituted 1,4,5,8-naphthalene diimide (NDI) compounds were characterized using fluorescence and phosphorescence spectroscopies, as well as nanosecond laser flash photolysis. The reactive intermediates were quantified as a function of the number of methylenes in the alkyl linker. Rate constants for photoinduced electron transfer (PET) to the singlet excited state of theNDIsvaried from 1.2 × 1010to 4.9 × 1010s–1. The yield of the long-lived amino ketyl radical ranged from 15% to 60% in compounds having 4 to 1 intervening methylenes between theNDIchromophore and the covalently attached carboxylic acid. A predominantly triplet state was observed upon direct excitation of the compound having the slowest PET. This T1state of theNDIswas reductively quenched by DABCO electron donor. The amino ketyl radical was unreactive toward electron donors but was found to react with the hydrogen atom donor β-mercaptoethanol. The compounds comprise a novel class of long-wavelength and strongly absorbing UV-activated chromophores that generate carbon-centered biradicals via direct 355 nm excitation in the absence of a cosensitizer.