In-situ NMR spectroscopic investigations of the organic photochromism in spiropyran and spiroxazine norbornens and their homopolymers

在紫外光(UV)照射下，螺吡喃和恶嗪的颜色发生变化，主要从无色变为紫色。这种颜色的变化是由从闭合螺环形式到开环花菁形式的可逆开环反应引起的。物理性质的变化，如偶极矩，被用于刺激响应材料的设计。对于这种材料的开发，参数，如辐照时转变为开放形式的程度或热环闭合反应的反应速率是重要的。此外，这些性质与存在的条件(溶剂、温度等)有关。例如，开放的花菁被极性溶剂稳定，从而减缓了热回流反应。该项目的一个目标是用原位核磁共振波谱研究螺吡喃和恶嗪降冰片烯的单体和聚合物的有机光致变色性。使用和发展核磁共振光谱学方法来研究有机光致变色是拟议项目的一个主要目标。螺吡喃在辐照后会发生降解反应。更深入和系统地了解螺吡喃和去甲螺恶嗪的光降解途径也是我们研究的重点，因为这些限制了此类系统的适用性。此外，螺吡喃和-恶嗪与(金属)离子的相互作用也在本项目的范围内，因为这种相互作用可以影响螺吡喃和-恶嗪的光致变色行为。更深入地了解这些相互作用的范围将允许有针对性地使用离子来影响介孔薄膜的传输特性。这些单体和聚合物是在Andrieu-Brunsen基团中合成的，将用于开发介孔二氧化硅薄膜中的光控离子传输。我们对这类螺吡喃和恶嗪的光解反应进行了原位核磁共振研究，所得结果可用于改进上述杂化材料。

Upon irradiation with ultraviolet light (UV) spiropyranes and -oxazines show a change in color mostly from colorless to purple. This change in color is caused by a reversible ring opening reaction from the closed spiro- to the open merocyanine-form. The changes induced in physical properties, like the dipole moment, are used for the design of stimuli responsive materials. For the development of such materials, parameters like the degree of conversion to the open form upon irradiation or reaction rates of the thermal ring closing reaction are important. Furthermore these properties are related to the conditions present (solvent, temperature, etc.). The open merocyanine is stabilized by polar solvents, e.g., and thus thermal back reaction is slowed down. A goal of the proposed project is the investigation of the organic photochromism of monomeric and polymeric spiropyran and -oxazine-norbornenes with in-situ NMR spectroscopy. The use and development of NMR-spectroscopic methods to investigate organic photochromism is a main objective of the proposed project. Spiropyrans show degradation reactions upon irradiation. A deeper and systematic understanding of the pathways of photodegradation of spiropyran and spiroxazine norbornens is also in the focus of our investigations, as these limit the applicability of such systems. Furthermore the interaction of spiropyrans and -oxazine with (metal) ions is within the scope of this project as such interactions can have an influence on the photochromic behavior of spiropyrans and -oxazines. A deeper knowledge of the scope of these interactions would allow for a targeted use of ions to influence transport properties in mesoporous films. The monomers and polymers are synthesized in the the group of Andrieu-Brunsen and shall be used for the development of photocontrollable ionic transport in mesoporus silica-films. Results obtained from our in-situ NMR investigations of such spiropyrans and -oxazines with respect to photodecomposition reactions can then be used to improve before mentioned hybrid materials.