具有强双光子吸收和高双光子荧光活性的全芳香DPP基共轭分子及其构建单/双光子荧光化学传感器研究

Two-photon absorption (2PA) and two-photon excitation fluorescence (2PEF) have many advantages over commonly UV-vis one-photon ones, including exclusive confinement of the excitation to the focal volume with high 3D resolution and reduced photobleaching and phototoxicity by virtue of the low-energy NIR excitation with greater depths of penetration. Organic conjugated molecules (small and polymeric compounds) with large 2PA cross sections have attracted considerable interests because of their significant applications in the areas of nonlinear optical materials, such as two-photon excited fluorescence microscopy, optical limiting, optical data storage, 3D-microfabrication, up-conversion lasing, photodynamic cancer therapy, and two-photon fluorescent probes. It is very desirable that 2PA materials not only have large 2PA cross sections but also exhibite good photo- and thermal-stability and so on, moreover, the functional units that can act with analytes to induce the significant changes of emission intensity or fluorescence color are also hoped earnestly if TPA materials are used as two-photon fluorescent probes such as for anion/metal ions. It is well known that conjugated polymers can offer a significant advantage over small chromophores for sensor applications, that is "singal amplification effect" and higher sensitivity due to their conjugated backbone allowing efficient electron delocalization and exciton migration over long distance. However,to the best of our knowledge, there have been a few fully aromatic conjugated polymers with very large 2PA cross-sections as well as conjugated polymer-based two-photon ion sensors reported in the literature.In this project, a series of fully aromatic 1,4-diketo-3,6-diarylpyrrolo[3,4-c]pyrrole (DPP)- containing copolymers were designed and synthesized by Suzuki cross-coupling between mono-/bis-substituted DPP and various aromatic or heteroaromatic monomers, and their one- and two-photon absorption and emission properties, sensing performance for fluoride, zinc and hydroxide ions, optical power limiting were investigated in order to develop novel high-performance and multifunctional two-photon active dyes. To the best of our knowlege, many attempts have been made to use DPP-based copolymers as highly luminescent, electroactive and photoactive materials, but there are few reports on the 2PA properties and applications of DPP-based conjugated molecules. These polymers studied here posess D-π-A-π-D-type repeating units, and some of them have specific functional units selectively for fluoride ion or zinc ion or Pt ion, etc. to endow them with very large 2PA cross-sections and strong two-photon excited fluorescence and exhibit promising optical limiting and sensing-ion properties which based on intramolecular charge transfer effect or complexation. Pre-experiments have been carried out and advanced the feasibility of the design ideas and the realization of the research objects.

尽管人们已经设计合成了大量双光子活性的共轭有机分子，但具有大双光子吸收截面（δ）的几乎都是以碳-碳双键或叁键为共轭桥，存在光、热及化学稳定性等问题，而且鲜见高δ共轭有机分子用作离子和/或分子双光子荧光化学传感器的成功报道。本项目通过3,6-二芳基吡咯并吡咯二酮（DPP）与某些芳基化合物的交叉Suzuki偶合,设计合成一系列包括带有功能活性单元的高光热稳定性全芳香DPP基共轭小分子和高分子，首次测定研究它们的强双光子吸收性质和高双光子激发荧光活性，首次构筑能够对某些阴/阳离子进行双光子荧光化学传感的全芳香大δ共轭有机荧光分子，建立全芳香DPP基双光子荧光共轭分子的化学组成、结构与性能及功能关系。本项目不仅拓展了DPP基共轭分子的种类和应用范围，而且为双光子科学和技术发展提供了新的高性能和多功能共轭有机高双光子活性材料体系，具有重要的理论意义和实际意义。

吡咯并吡咯二酮（DPP）衍生物是商品可获得或易于合成的一类高性能有机颜料，其杂环结构和强吸电子性已被用作构筑有机场效应晶体管和有机太阳能电池材料的构筑单元，我们认为其结构和电子特性也可用于构筑新型刺激响应荧光材料。本项目以DPP为受体中心，通过不同的芳环作为共轭桥连接各种电子给体，并通过变化N-烷基链长等方式，设计合成了一系列含电子给体和受体的D-A型分子，研究了它们的双光子吸收和双光子荧光性质、对氟离子的单/双光子荧光传感性质、聚集强化荧光发射和力刺激荧光变色行为，首次提出并确证DPP是构筑全芳香光热稳定性的双光子荧光材料有效π中心，它们具有大的双光子吸收截面，发射红和近红外双光子激发荧光，可成为荧光影像和光限幅等方面应用的高性能材料体系。 本项目不仅实现了含单内酰胺氢DPP衍生物对氟离子的单/双光子荧光传感，而且揭示了含双内酰胺氢聚合物能在固态下传感和富集氟离子，这在环境检测和保护等方面具有重要应用潜力。本项目构筑的线型和多支化受体共轭桥D-A分子呈现多态发射性质，具有聚集强化和大的双光子吸收截面；某些D-A分子呈现独特的力致和热致荧光变色行为，获得了少见报道的大的力致蓝移和进一步热致蓝移材料，光谱位移量接近200纳米。本项目还发现，简单的商品颜料经长链烷基化后，即可获得力致大蓝向位移荧光材料，而且它们的热致荧光变色呈现独特的温度依赖性，可以通过控制冷结晶温度实现红移或蓝移，即双向热致致荧光变色性，大大丰富了有机力致和热致荧光变色材料种类。本项目工作还揭示硫代内酰胺不仅能使p-型场效应晶体管变成双极场效应晶体管，而且能大大强化载流子迁移率。在本项目经费资助下发表SCI论文16篇，其中中科院JCR-I区论文8篇，II区论文4篇，III区论文4篇，1篇被评为Hot论文。