Development of Stable Neutral Radicals Having an Unconventional Spin-Delocalized Nature

有机开壳层分子作为一种短寿命的活性中间体，近年来由于各种稳定化技术的发展，已成为新型分子基功能材料的重要组成部分。为了加强这一研究领域的基础，关键是建立新的设计标准和合成方法的开壳层分子系统的结构和电子显着的特点。在这项研究中，我们已经合成和表征了新的有机开壳层系统具有拓扑控制和极端离域自旋密度分布的性质，展示了异国情调的电子功能源自这些电子自旋结构。(1)基于动态电子自旋行为的新型热致变色的实现：我们已经实验确定了低温下在溶液状态下形成的Ti-二聚体的化学结构，揭示了具有12-中心-2-电子性质的新的C-C键。此外，自由基聚集体的芳香性在我们的研究中首次提出。(2)纯有机开壳层体系自旋中心转移开关体系的实现：我们制备了TTF连接的6-oxophenalenoxyl中性自由基体系，并建立了基于分子内电子转移的溶剂和温度控制的完全自旋开关体系。(3)首次合成、分离和表征了离域单重态双自由基烃，其表现出最高的室温电导率作为单组分烃，并且对于没有电子给体或受体取代基的纯烃具有异常大的双光子吸收截面。

Organic open-shell molecules, widely recognized as short-lived reactive intermediates, have recently drawn attention as building blocks for new molecule-based functional materials, since various stabilization techniques have been developed. In order to strengthen the basis of this research field, it is crucial to establish novel design criteria and synthetic methodologies of open-shell molecular systems with structurally and electronically salient features. In this study, we have synthesized and characterized new organic open-shell systems having topologically-controlled and extremely delocalized spin-density distribution natures, demonstrating exotic electronic features originating from these electronic spin structures. (1) realization of novel thermochromism based on dynamic electron-spin behavior : We have experimentally determined chemical structure of Ti-dimer formed in a solution state at low temperature, revealing a new C-C bond with 12-center-2-electron nature. Furthermore, aromaticity of a radical aggregate was first proposed in our study. (2) realization of the switching system in terms of spin-center transfer of purely organic open-shell system : We have prepared TTF-linked 6-oxophenalenoxyl neutral radical system, and created solvent-and temperature-controlled complete spin-switching system based on intramolecular electron transfer. (3) The delocalized singlet biradical hydrocarbons were first synthesized, isolated, and characterized, showing the highest room-temperature electric conductivity as single-component hydrocarbon, and exceptionally large two-photon absorption cross sections for pure hydrocarbon with no electron-donor or-acceptor substituents.