The BODIPY scaffold as a core chromophore for extended, oligomeric, and helically chiral π-systems

本项目将合成和研究基于BODIPY基序的新型荧光团。该小组先前的工作表明，简单的氧化反应可以用来构建具有改进性能的低聚染料。桥接乙醇单元或苯环使用。在第一个工作包中，为了通过氮桥联的BODIPY二聚体通过Buchwald-Hartwig反应得到被α-氨基取代的BODIPYs，将使用被α-氨基取代的BODIPYs。据说在氧化条件下，它们在β-位置经历环闭合，形成桥接吡咯体系。以这种方式发展起来的策略要加以扩展，以达到类似的低聚体系。不对称的BODIPY单体，一方面携带一个氯取代基，另一方面携带一个氨基取代基，在这里被使用。线性体系和循环体系的形成是可以想象的，然后它们应该被氧化成完全共轭π体系。作为直接氧化的替代方案，也有可能通过与β-位置的醛反应使体系硬化，因此在进一步氧化后，通过环吡啶体系连接的BODIPYs应该是可以得到的。本文将详细研究这些化合物的光物理性质和结构性质。第二个工作包是基于几个BODIPY亚基的螺旋π体系的构建和光物理研究。将这种螺旋手性化合物分离成对映异构体或对映选择性结构，应该可以发出具有相对高的胶值的圆偏振光（cpL）。合成思路是基于首先生成具有桥接亚甲基单位的β-连接BODIPY低聚物。随后，通过剩余的游离β'位置发生氧化，生成桥接五元环，形成C - C键。这种特殊的几何排列应该提供构型稳定的螺旋分子，从少到四个亚基。将硼中心的中心手性转变为螺旋手性的策略有助于有针对性地生成P-或m -螺旋手性物质。此外，还将研究螺旋的不对称是否通过电荷转移或FRET效应提高cpL效率，例如通过连接终端电子供体。

In this project, novel fluorophores based on the BODIPY motif will be synthesized and investigated. Previous work by the group has shown that simple oxidation reactions can be used to construct oligomeric dyes with improved properties. Bridging ethano units or benzannulations were used.In a first work package, BODIPYs substituted by α-amino groups are to be used in order to obtain BODIPYs substituted with α-chlorine by means of the Buchwald-Hartwig reaction via nitrogen-bridged BODIPY dimers. These are said to undergo ring closure at the β-position under oxidative conditions to form the bridging pyrrole system. The strategy developed in this way is to be expanded in order to arrive at analogous oligomeric systems. Unsymmetrical BODIPY monomers, which carry a chlorine substituent on the one hand and an amino substituent on the other hand, are to be used here. The formation of linear as well as cyclic systems is conceivable, which should then be oxidized to fully conjugated π systems. As an alternative to direct oxidation, there is also the possibility of stiffening the system by reaction with aldehydes in the β-position, so that after further oxidation BODIPYs linked via annulated pyridine systems should be obtainable. The photophysical and structural properties of these compounds will be studied in detail.The second work package deals with the construction and photophysical investigation of helical π-systems based on several BODIPY subunits. A separation into enantiomers or an enantioselective construction of such helical-chiral compounds should make it possible to emit circularly polarized light (cpL) with comparatively high glum values. The synthetic idea is based on first generating β-linked BODIPY oligomers with a bridging methylene unit. Subsequently, an oxidation should take place via the remaining free β'-position, which generates a bridging five-membered ring with the formation of a C C bond. This special geometric arrangement should provide configurationally stable helical molecules from as little as four subunits. A strategy that transfers central chirality at the boron center into helical chirality should help to generate P- or M-helical chiral species in a targeted manner. In addition, it is to be investigated whether desymmetrization of the helix, e.g. by attaching a terminal electron donor, increases the cpL efficiency via charge transfer or FRET effects.