Nitronyl Nitroxide Bifunctionalized Electron-Poor Chromophores: Synthesis of Stable Dye Biradicals by Lewis Acid Promoted Desilylation.
Nitronyl Nitroxide Bifunctionalized Electron-Poor Chromophores: Synthesis of Stable Dye Biradicals by Lewis Acid Promoted Desilylation.
复制标题
硝基硝基氧双功能化贫电子发色团：通过路易斯酸促进脱甲硅烷基化合成稳定的染料双自由基
DOI：
10.1021/acs.joc.0c02613
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发表时间：
2021
期刊：
影响因子：
--
通讯作者：
F. Würthner
中科院分区：
文献类型：
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作者：
R. Rausch;A.-M. Krause;I. Krummenacher;H. Braunschweig;F. Würthner
带π核的开壳有机分子在光学、电子和磁性领域有着广泛的应用，但往往存在快速分解或缺乏合成可及性的问题。在这方面，硝基氮氧化物由于其沿O-N-C-N-O五元的高度自旋离域而成为稳定（双）自由基的有希望的候选者。不幸的是，到目前为止，它们仅限于富电子系统。为了克服这一限制，我们开发了一种合成方法，通过氟化硼对各自的硅化前体进行选择性脱保护/氧化，然后用正硅酸四乙酯进行猝灭，用硝基氮氧化物自由基基团对电子贫发色团（Ered= - 1158 mV）进行双自旋修饰。以苝酰亚胺（PBI）、异靛蓝（IIn）和二酮吡罗（DPP）为着色剂，经高碘酸盐氧化，最终得到了台架稳定化合物PBI - nn、IIn - nn、PhDPP-NN、ThDPP-NN和FuDPP-NN。发色团的吸收光谱特征保持在开壳状态，并与原始母体化合物的吸收光谱特征相匹配，这使得对其光学性质的优先预测成为可能。因此，我们实现了双自旋标记，同时保持了缺电子发色团的固有性质完整。
Open shell organic molecules bearing π-cores are of great interest for optical, electronic, and magnetic applications but frequently suffer fast decomposition or lack synthetic accessibility. In this regard, nitronyl nitroxides are promising candidates for stable (bi-)radicals due to their high degree of spin delocalization along the O–N–C–N–O pentad unit. Unfortunately, they are limited to electron-rich systems so far. To overcome this limitation, we developed a synthetic procedure for the twofold spin decoration of electron-poor chromophores (Ered= −1158 mV) with nitronyl nitroxide radical moieties via selective deprotection/oxidation of the respective silylated precursors with boron fluoride and subsequent quenching with tetraethyl orthosilicate. Nitronyl nitroxide biradicals PBI–NN, IIn–NN, PhDPP–NN, ThDPP–NN, and FuDPP–NN bridged by perylene bisimide (PBI), isoindigo (IIn), and diketopyrrolopyrrole (DPP) pigment colorants were finally obtained as bench stable compounds after periodate oxidation with yields of 60–81%. The absorption spectral signatures of the chromophores remain preserved in the open shell state and match the ones of the pristine parent compounds, which allowed ana prioriprediction of their optical properties. Consequently, we achieved twofold spin labeling while keeping the intrinsic properties of the electron deficient chromophores intact.