Wicklein André, Lang Andreas, Muth Mathis, Thelakkat Mukundan
Department of Macromolecular Chemistry I, Applied Functional Polymers, Universität Bayreuth, 95440 Bayreuth, Germany.
J Am Chem Soc. 2009 Oct 14;131(40):14442-53. doi: 10.1021/ja905260c.
Tailor-made synthesis and structure-property relationship of several swallow-tail N-substituted perylene bisimide (PBI) dyes are presented. PBI derivatives were synthesized by two distinct synthetic approaches, the details being evaluated herein. All the PBIs carry either alkyl swallow-tail or oligoethylenglycolether (OEG) swallow-tail moieties as N-substituents, and many of them are unsymmetrically substituted. We avoided substitution at bay positions of the perylene core to maintain the planarity and strong pi-pi interactions, which favor intermolecular order and charge carrier transport. The thermotropic behavior, which is strongly influenced by the nature of the substituents was investigated using differential scanning calorimetry (DSC), polarization optical microscopy (POM), and X-ray diffraction measurements (XRD). The introduction of OEG swallow-tail units facilitates thermotropic liquid crystalline behavior in most cases and the unsymmetrical substitution allowed the tuning of the mesophase-width. The mesophases exhibit characteristic columnar hexagonal (Col(h)) packing arising from pi-pi interactions between cofacially orientated perylene molecules. Thus, the inherent tendency of PBI molecules for crystallization could be effectively suppressed by incorporating flexible OEG swallow-tail units only at imide positions. This molecular design was crucial to obtain liquid crystallinity and intracolumnar long-range order. The substituents did not influence the electronic energy levels such as HOMO and LUMO.
本文介绍了几种燕尾状 N - 取代苝二酰亚胺（PBI）染料的定制合成及其结构 - 性能关系。PBI 衍生物通过两种不同的合成方法制备，本文将对其细节进行评估。所有的 PBI 均带有烷基燕尾或聚乙二醇醚（OEG）燕尾部分作为 N - 取代基，其中许多是不对称取代的。我们避免在苝核的湾区位置进行取代，以保持平面性和强烈的 π - π 相互作用，这有利于分子间的有序排列和电荷载流子传输。使用差示扫描量热法（DSC）、偏光光学显微镜（POM）和 X 射线衍射测量（XRD）研究了受取代基性质强烈影响的热致行为。在大多数情况下，引入 OEG 燕尾单元有助于热致液晶行为，不对称取代允许调节中间相宽度。中间相表现出由共面取向的苝分子之间的 π - π 相互作用产生的特征性柱状六方（Col(h)）堆积。因此，仅通过在酰亚胺位置引入柔性 OEG 燕尾单元，可以有效地抑制 PBI 分子的固有结晶倾向。这种分子设计对于获得液晶性和柱内长程有序至关重要。取代基不影响诸如 HOMO 和 LUMO 等电子能级。
