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首页> 外文期刊>Chemistry: A European journal >Tuning the Stacking Properties of C_3-Symmetrical Molecules by Modifying a Dipeptide Motif
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Tuning the Stacking Properties of C_3-Symmetrical Molecules by Modifying a Dipeptide Motif

机译：通过修改二肽基序来调节C_3对称分子的堆叠特性

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摘要

C_3-symmetrical molecules are described which consists of a 1,3,5-benzenetricarboxamide core extended with dipeptide fragments bearing peripheral mesogenic groups. Small structural modifications in the dipeptide fragment have been performed to demonstrate their influence on the stability of the stacks and on the order within the self-assemblies formed. Seven C_3-symmetrical discs have been investigated, all with different combinations of glycine, L- and/or D-phenylalanine in the dipeptide fragments. Characterization of these discotics in the neat state using differential scanning calorimetry (DSC), X-ray diffraction (XRD) and polarized optical microscopy (POM) and in solution with circular dichroism (CD), UV-visible spectroscopy, low-concentration proton nuclear magnetic resonance and IR spectroscopy reveals that there is a clear trend in the stack stability, going from the glycine-phenylalanine motifs to the phenylalanine-phenylalanine ones. The combination of a larger hydrophobic core, more confinement of space and the possibility of additional pi-pi interactions leads to more stable stacks. Surprisingly, the weakest stacks consist of discotics of which the center is extended with L-phenylalanyl-glycines and not of discotics of which the center is extended with the glycyl-L-phenylalanine se-quences. Furthermore, the XRD investigations show that it is difficult to form well-ordered self-assemblies in the neat state. And, CD measurements point out that some of the discs have a very complex energy landscape in solution. These observations suggest that small differences in the balance between the secondary interactions originating from the benzenetricarboxamide core and the dipeptide fragments, have a strong influence on the order within the stack. From these results it can be concluded that subtle modifications in the peptide fragments of the discs cause significant changes in the stacking properties, stressing the importance of understanding the self-assembly mechanism of each discotic in order to clarify its self-assembly behavior.
机译：描述了C_3对称分子，其由1,3,5-苯三甲酰胺核心组成，该核心延伸有带有外围介晶基团的二肽片段。已经对二肽片段进行了小的结构修饰，以证明它们对堆叠稳定性和所形成的自组装体中的顺序的影响。已经研究了七个C_3对称盘，它们在二肽片段中均具有甘氨酸，L-和/或D-苯丙氨酸的不同组合。使用差示扫描量热法（DSC），X射线衍射（XRD）和偏振光学显微镜（POM）以及在溶液中使用圆二色性（CD），紫外可见光谱，低浓度质子核对这些盘状菌进行纯净表征磁共振和红外光谱表明，从甘氨酸-苯丙氨酸基序到苯丙氨酸-苯丙氨酸基序，堆栈稳定性存在明显的趋势。更大的疏水核，更多空间限制和附加的pi-pi相互作用的可能性的结合导致了更稳定的堆叠。出人意料的是，最弱的堆叠包括其中心延伸有L-苯丙氨酸-甘氨酸的圆盘，而不是其中心延伸有甘氨酰-L-苯丙氨酸序列的圆盘。此外，XRD研究表明，很难在整齐的状态下形成有序的自组装体。而且，CD测量指出，某些光盘在解决方案中具有非常复杂的能量格局。这些观察结果表明，源自苯三甲酰胺核心和二肽片段的次级相互作用之间的平衡差异小，对堆叠中的顺序有很大影响。从这些结果可以得出结论，圆盘的肽片段中的细微修饰会导致堆叠特性发生重大变化，从而强调了理解每个圆盘的自组装机制以阐明其自组装行为的重要性。

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