Saeki Hidenori, Sakamaki Daisuke, Fujiwara Hideki, Seki Shu
Department of Molecular Engineering , Graduate School of Engineering , Kyoto University , Nishikyo-ku , Kyoto 615-8510 , Japan . Email:
Department of Chemistry , Graduate School of Science , Osaka Prefecture University , Naka-ku , Sakai-shi , Osaka 599-8531 , Japan . Email:
Chem Sci. 2019 Aug 29;10(39):8939-8945. doi: 10.1039/c9sc01739a. eCollection 2019 Oct 21.
How strong are van der Waals interactions in determining the final outcome of self-assembled structures of small molecular systems? Herein we report isolable phthalocyanine (Pc) dimers bound by π-π interactions between monomeric Pcs which can be handled as single entities. Pc dimers have been continuously investigated as one of the simplest models of Pc aggregates. Pcs were substituted with eight dihydrodiazapentacene (DHDAP) moieties on the periphery, which act as pillar-like π-planes and these molecules form H-type dimers with the help of synergetic π-π interactions between two co-facial Pc rings and among the pillar-like DHDAP moieties. The dimer structures were fully confirmed by 1D and 2D NMR, ESR, and electronic absorption measurements. The dissociation of these dimers was observed in particular solvents such as -dichlorobenzene, due to the good solubility of the larger π-conjugated molecules. On the other hand, in ethyl acetate the monomers were metastable species and underwent selective dimerization. Interestingly in THF, neither the dimerization of the monomers nor the dissociation of dimers was observed, suggesting that both the dimers and the monomers were kinetically well stabilized. For hours to days, we can handle these dimers as "a molecule" not only in solution but also even in mass spectrometry under ionization conditions without significant dissociation.
范德华相互作用在决定小分子系统自组装结构的最终结果方面有多强？在此，我们报道了通过单体酞菁之间的π-π相互作用结合的可分离酞菁（Pc）二聚体，其可以作为单个实体进行处理。Pc二聚体作为Pc聚集体最简单的模型之一，一直受到持续研究。Pc在其外围被八个二氢二氮杂并五苯（DHDAP）部分取代，这些部分充当柱状π平面，并且这些分子借助两个共面Pc环之间以及柱状DHDAP部分之间的协同π-π相互作用形成H型二聚体。通过一维和二维核磁共振、电子自旋共振和电子吸收测量对二聚体结构进行了充分确认。由于较大π共轭分子具有良好的溶解性，在诸如对二氯苯等特定溶剂中观察到了这些二聚体的解离。另一方面，在乙酸乙酯中，单体是亚稳物种并发生选择性二聚化。有趣的是，在四氢呋喃中，既未观察到单体的二聚化，也未观察到二聚体的解离，这表明二聚体和单体在动力学上都得到了很好的稳定。在数小时至数天的时间里，我们不仅可以在溶液中，甚至在电离条件下的质谱分析中，将这些二聚体作为“一个分子”来处理，而不会有明显的解离。
