Harimoto Takashi, Ishigaki Yusuke
Department of Chemistry, Faculty of Science, Hokkaido University, Sapporo, 060-0810, Japan.
Present address: Institute for Molecular Science, Myodaiji, Okazaki, 444-8787, Japan.
Chemistry. 2025 Jan 14;31(3):e202403273. doi: 10.1002/chem.202403273. Epub 2024 Nov 22.
Electrochromic systems capable of switching absorption in the near-infrared (NIR) region (750-2500 nm) are attractive from the viewpoint of applications for material and life science, and thus several examples have been reported to date. In general, the development of organic-based systems is needed to reduce the environmental impact and improve biocompatibility. Although extending the switchable spectral range is crucial for the application of organic electrochromic molecules, the switching of NIR absorption based on redox interconversion is still a challenging issue regarding reversibility and durability during interconversion. To overcome this potential instability, the introduction of heteroatoms into the molecular backbone and/or π-extension could be useful strategies in terms of effective delocalization of charge and spin in the corresponding redox states. In this review, we focus on redox-active well-defined small molecules that enable ON/OFF switching of NIR absorption based on precise control of the redox states, and present recent studies on their intrinsic electrochemical and spectroscopic properties and/or structural characterization of their charged states.
能够在近红外（NIR）区域（750 - 2500 nm）切换吸收的电致变色系统，从材料和生命科学应用的角度来看具有吸引力，因此迄今为止已有若干实例报道。一般来说，需要开发基于有机的系统以减少环境影响并提高生物相容性。虽然扩展可切换光谱范围对于有机电致变色分子的应用至关重要，但基于氧化还原互变的近红外吸收切换在互变过程中的可逆性和耐久性方面仍然是一个具有挑战性的问题。为了克服这种潜在的不稳定性，在分子主链中引入杂原子和/或进行π-扩展，在相应氧化还原状态下电荷和自旋的有效离域方面可能是有用的策略。在本综述中，我们关注基于氧化还原状态的精确控制能够实现近红外吸收开/关切换的氧化还原活性明确的小分子，并介绍其固有电化学和光谱性质以及/或其带电状态的结构表征的最新研究。
