荧光染料在生命科学和医学领域发挥着重要的作用。通过合理的结构修饰，荧光染料可以被用于检测生物分子、可视化生理过程、实现荧光成像手术导航等，极大推动了该领域的发展进程，因此荧光染料的发展长期以来备受关注。传统的荧光染料发光波长大多在可见光区（400-700 nm）和近红外一区（700-900 nm），由于组织对该波段光的吸收和散射导致其穿透性不好，限制了传统荧光染料在生物成像中的应用。生物组织对近红外二区（900-1700 nm）光线的吸收和散射弱，并且无组织自荧光，因此近红外二区荧光成像具有组织穿透性好、成像信噪比高等优点。然而，由于近红外二区荧光染料的最低激发能低，极易通过振动失活，且普遍存在合成修饰困难的问题，其相比传统荧光染料数量非常少、选择范围有限。因此开发近红外二区荧光染料对于推动生物成像的发展具有非常重要的意义。

本论文针对近红外二区荧光染料数量少、发光信号弱的问题，发展了一种通过分子间电荷转移作用活化碳碳偶联的合成方法，以该方法为基础合成了一系列基于苯并双噻二唑（BBTD）的近红外二区荧光染料，并合成了基于氮杂氟硼荧（aza-BODIPY）的近红外二区荧光染料，研究了通过能量传递对其发光性能的调控。具体工作如下：

第一，发展了一种简单、高效、无需金属催化的碳碳偶联合成方法，该方法利用富电和缺电的两种化合物之间的相互作用使之形成电荷转移复合物，拉近了分子的空间距离，使分子被活化并发生偶联反应。相比常用的钯催化碳碳偶联反应，该方法不仅简化了合成过程，而且能够得到传统合成方法难以实现的全新的分子结构。以该方法为基础，合成了一系列基于BBTD的近红外二区分子，通过改变一侧给体基元的给电子强度可以实现对荧光分子发射波长的精细调控。

第二，合成了三种发光在近红外二区的aza-BODIPY，并以其作为能量受体，具有聚集诱导发光（AIE）性质的分子为能量给体，制备了三种超分子组装体系，研究了通过能量传递对受体分子发光性能的调控。初步结果表明，相比能量受体，组装体的发光强度均有不同程度的增强。其中，在能量给受体中均引入四重氢键基元的组装体系效果最为显著，当受体掺杂量为5%时，组装体的发光强度是受体分子的7.6倍，极大增强了受体分子的发光强度。

Fluorescent dyes are playing important roles in the fields of life sciences and medicine. Through reasonable structural modification, fluorescent dyes can be used to detect biomolecules, visualize physiological processes, realize fluorescence imaging guided surgery and so on, which have greatly promoted the development of these fields. Therefore, the development of fluorescent dyes has attracted much attention for a long time. Traditional fluorescent dyes mostly emit in the visible region (400-700 nm) and the first near-infrared region (700-900 nm). Due to the tissue scattering and absorption, the penetration of traditional fluorescent dyes is poor, which limits their application in biological imaging. By contrast, fluorescence imaging in the NIR-II window (900-1700 nm) displays less tissue scattering, absorption and auto-fluorescence, which contribute to deeper tissue penetration and higher signal-to background ratios. However, excited NIR-II dyes tend to fall back to lower energy states through non-radiative decays owing to lower energy gap and their synthesis and modification are difficult, which result in the lack of NIR-II dyes. Therefore, the development of NIR-II dyes is of great significance for the field of biological imaging.

Herein, in the light of the problems of NIR-II dyes, such as scarce choices and weak fluorescence signal, a carbon-carbon coupling reaction activated by charge transfer interaction has been developed, on the basis of which, a series of NIR-II dyes based on benzothiadiazole (BBTD) were synthesized. And we also synthesized NIR-II dyes based on aza-BODIPY, the property control of which by energy transfer was studied. The specific work is as follows:

1. A simple, efficient and metal-free carbon-carbon coupling reaction was developed. Charge transfer between electron-rich molecules and electron-dificient ones closes their space distance to form electon donor-acceptor (EDA) complexes, which results in the coupling reaction. Compared with Pd-catalyzed C-C coupling reactions commonly used, this method not only simplifies the synthesis process, but also can be used to obtain new molecular structures which is difficult to be synthesized by traditional methods. A series of NIR-II dyes based on benzothiadiazole (BBTD) were synthesized using this coupling reaction. The emission wavelengths of these dyes could be fine tuned by changing electron-donor unit of one side.

2. Three NIR-II dyes based on aza-BODIPY have been synthesized, which were used as energy acceptors for preparation of supermolecular assembly systems together with aggregation-induced emission luminogens (AIEgens) as energy donors. Three kinds of supermolecular assembly systems have been constructed, and the property control of acceptors by energy transfer was studied. Preliminary results show that the emission intensity of the assembly systems was enhanced in different degrees compared with that of the energy acceptors. Among them, the assembly system which introduced quadruple hydrogen-bond unit (Upy) into energy donors and acceptors showed the most significant effect. The emission intensity of this assembly system was 7.6 times than that of the acceptors, which greatly enhanced the emission intensity of the acceptors.