Luo Ming, Chen Dafa, Li Qian, Xia Haiping
Shenzhen Grubbs Institute, Department of Chemistry, Southern University of Science and Technology, Shenzhen 518055, China.
State Key Laboratory of Physical Chemistry of Solid Surfaces, College of Chemistry and Chemical Engineering, Xiamen University, Xiamen 361005, China.
Acc Chem Res. 2023 Apr 18;56(8):924-937. doi: 10.1021/acs.accounts.2c00750. Epub 2023 Jan 30.
ConspectusAromatic compounds are important in synthetic chemistry, biomedicines, and materials science. As a special type of aromatic complex, transition-metal-based metallaaromatics contain at least one transition metal in an aromatic framework. The chemistry of metallaaromatics has seen much progress in computational studies and synthetic methods, but their properties and applications are still emerging. In recent years, we have disclosed a series of metal-centered conjugated polycyclic metallacycles in which a carbon chain is chelated to a metal center through at least three metal-carbon bonds. These are termed carbolong complexes and exhibit good stability to water, oxygen, light, and heat on account of their polydentate chelation and aromaticity, making them easy to handle. Carbolong complexes are not only special π-conjugated aromatics but also organometallics; therefore, they have the properties of both species. In this Account, we showcase the recent advances in their applications based on their different properties.First, carbolong complexes are a special kind of π-conjugated aromatic, with the ability to transmit electrons, allowing them to function as single-molecule conductors and candidates for electron transporting layer materials (ETLs) in solar cells. A series of carbolong complexes have been proved to be useful as achievable ETLs which enhance device performance in both organic solar cells and perovskite solar cells.Second, due to the involvement of d orbitals in the conjugation, carbolong complexes normally exhibit strong and broad absorption, even in some cases extending to the near-infrared region (NIR). The absorbed optical energy can be converted into light, heat, and ultrasound; consequently, carbolong compounds can be used as core moieties in smart materials. For example, 7C carbolong complexes were found to exhibit aggregation-enhanced near-infrared emission (AIEE). Some 12C carbolong complexes have been designed into the core moieties of NIR-responsive polymers, such as cylindrical NIR-responsive materials, self-healing materials, and shape memory materials. In contrast to the stereotypically toxic osmium compounds such as the highly toxic OsO, some osmium carbolong complexes exhibit low cell cytotoxicity and good biocompatibility; consequently, they also have potential applications in the biomedical area. For example, benefiting from broad absorption in the NIR, 9C and 12C carbolong complexes have been used in photoacoustic imaging and photothermal therapy, respectively. In addition, photodynamic therapeutic applications which take advantage of a carbolong peroxo complex are discussed.Third, as special transition-metal complexes chelated by carbon-based ligands, a carbolong peroxo complex has displayed catalytic activity in the dehydrogenation of alcohols and a bimetallic carbolong complex has been used to catalyze difunctionalization reactions of unactivated alkenes.Overall, aromatic carbolong complexes have been applied to photovoltaics, smart materials, phototherapy, and catalytic reactions. Moving forward, we hope that this Account will shed light on future studies and theoretical research and encourage more discoveries of the properties of other metallaaromatics.
概述
芳香族化合物在合成化学、生物医学和材料科学中都很重要。作为一种特殊类型的芳香配合物，基于过渡金属的金属芳香族化合物在其芳香骨架中至少含有一种过渡金属。金属芳香族化合物的化学在计算研究和合成方法方面取得了很大进展，但其性质和应用仍在不断涌现。近年来，我们已经披露了一系列以金属为中心的共轭多环金属环，其中碳链通过至少三个金属 - 碳键与金属中心螯合。这些被称为碳龙配合物，由于其多齿螯合和芳香性，它们对水、氧气、光和热表现出良好的稳定性，使其易于处理。碳龙配合物不仅是特殊的π共轭芳香族化合物，也是有机金属化合物；因此，它们具有这两类物质的性质。在本综述中，我们基于它们的不同性质展示了其应用的最新进展。
首先，碳龙配合物是一种特殊的π共轭芳香族化合物，具有传输电子的能力，使其能够作为单分子导体以及太阳能电池中电子传输层材料（ETL）的候选材料。一系列碳龙配合物已被证明可用作可行的ETL，可提高有机太阳能电池和钙钛矿太阳能电池的器件性能。
其次，由于d轨道参与共轭，碳龙配合物通常表现出强烈而宽泛的吸收，甚至在某些情况下延伸至近红外区域（NIR）。吸收的光能可以转化为光、热和超声波；因此，碳龙化合物可作为智能材料的核心部分。例如，发现7C碳龙配合物表现出聚集增强近红外发射（AIEE）。一些12C碳龙配合物已被设计成近红外响应聚合物的核心部分，如圆柱形近红外响应材料、自愈材料和形状记忆材料。与典型有毒的锇化合物如剧毒的OsO不同，一些锇碳龙配合物表现出低细胞毒性和良好的生物相容性；因此，它们在生物医学领域也有潜在应用。例如，受益于在近红外区域的宽泛吸收，9C和12C碳龙配合物分别已用于光声成像和光热疗法。此外，还讨论了利用碳龙过氧配合物的光动力治疗应用。
第三，作为由碳基配体螯合的特殊过渡金属配合物，碳龙过氧配合物在醇的脱氢反应中表现出催化活性，并且一种双金属碳龙配合物已被用于催化未活化烯烃的双官能化反应。
总体而言，芳香族碳龙配合物已应用于光伏、智能材料、光疗和催化反应。展望未来，我们希望本综述能为未来的研究和理论研究提供启示，并鼓励更多关于其他金属芳香族化合物性质的发现。
