Ehni Philipp, Bauch Soeren M, Becker Patrick M, Frey Wolfgang, Zens Anna, Kästner Johannes, Molard Yann, Laschat Sabine
Institut für Organische Chemie, Universität Stuttgart, Pfaffenwaldring 55, D-70569 Stuttgart, Germany.
Institut für Theoretische Chemie, Universität Stuttgart, Pfaffenwaldring 55, D-70569, Germany.
Phys Chem Chem Phys. 2022 Sep 21;24(36):21617-21630. doi: 10.1039/d2cp02237k.
Aiming at merocyanine dyes with good linear optical and self-assembly properties, a series of rigid mono-, bi- and tricyclic merocyanines with - and -donor units as well as keto or malodinitrile acceptor units was prepared by a convergent approach. With particular focus on tailoring the donor unit, a selection of appropriate derivatives was investigated with respect to their dye properties in solution and in the bulk (UV/Vis, fluorescence, temperature-dependent fluorescence, lifetime). Determination of fluorescence quantum yields revealed the importance of the donor unit and the chromophore size. Larger chromophores and -donors were beneficial for strong emission in solution, whereas small chromophores and -donors favored emission in the solid state. To rationalize the different optical properties depending on their donor unit, density functional theory (DFT) calculations were performed. Liquid crystalline derivatives were additionally studied by optical polarization microscopy, differential scanning calorimetry, and X-ray diffraction experiments. For merocyanines with -donor, fluorinated side chains were mandatory to get stable enantiotropic SmA phases regardless of chromophore size, side chain lengths or acceptor unit. Increased mesophase widths (up to 134 K) were observed upon increasing the chromophore lengths, chain lengths (up to C) and F/C ratio in the side chain. On the other hand, merocyanines with -donor and keto acceptor showed enantiotropic SmA phases in the presence of simple alkoxy side chains. The tricyclic merocyanine with -donor shows an additional SmE phase at lower temperatures. The results revealed the importance of the donor unit to balance optical and mesomorphic properties in merocynanines.
针对具有良好线性光学和自组装性能的部花青染料，通过收敛法制备了一系列具有给体单元以及酮或丙二腈受体单元的刚性单环、双环和三环部花青。特别关注给体单元的剪裁，研究了一系列合适的衍生物在溶液和本体中的染料性质（紫外/可见光谱、荧光、温度依赖荧光、寿命）。荧光量子产率的测定揭示了给体单元和发色团大小的重要性。较大的发色团和给体有利于溶液中的强发射，而较小的发色团和给体则有利于固态发射。为了合理化取决于给体单元的不同光学性质，进行了密度泛函理论（DFT）计算。还通过光学偏振显微镜、差示扫描量热法和X射线衍射实验对液晶衍生物进行了研究。对于具有给体的部花青，无论发色团大小、侧链长度或受体单元如何，氟化侧链对于获得稳定的近晶A相是必不可少的。随着发色团长度、链长度（至C）和侧链中F/C比的增加，观察到中间相宽度增加（高达134 K）。另一方面，具有给体和酮受体的部花青在存在简单烷氧基侧链的情况下显示近晶A相。具有给体的三环部花青在较低温度下显示额外的近晶E相。结果揭示了给体单元在平衡部花青的光学和介晶性质方面的重要性。
