Department of Applied Chemistry, School of Engineering, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8656, Japan.
J Am Chem Soc. 2010 Jan 27;132(3):960-6. doi: 10.1021/ja904063r.
Discrete, well-defined stacks of the polarized aromatic pyrene-4,5-dione (1) were assembled in the cavities of organic-pillared coordination cages (2). The number (n) of stacked guests depends on the pillar length, and up to quintuple stacks (n = 5) were observed when long (16.5 A) organic pillar ligands were incorporated. As previously reported, pyrene-4,5-dione (1) assembles into infinite columnar stacks in the solid state, but the present work demonstrates that the polarized 1 has a strong propensity to stack in layers even in the absence of crystal packing effects. For n = 2 and 3 structures, crystallographic studies revealed that 1 stacks by pi-pi interactions in the cavity in such a way that a net dipole moment is canceled. These results emphasize the important role of dipole-dipole interactions as well as pi-stacking interactions in the formation of columnar stacks of 1.
堆积的离散、明确的芳香族芘-4,5-二酮（1）层被组装在有机柱撑配位笼（2）的空腔中。堆积的客体数量（n）取决于支柱的长度，当使用长（16.5A）有机支柱配体时，观察到多达五重堆积（n=5）。如前所述，芘-4,5-二酮（1）在固态中组装成无限柱状堆积，但本工作表明，即使没有晶体堆积效应，极化的 1 也具有强烈的层状堆积倾向。对于 n=2 和 3 的结构，晶体学研究表明，1 通过空腔中的 pi-pi 相互作用堆积，从而抵消了净偶极矩。这些结果强调了偶极-偶极相互作用以及 pi 堆积相互作用在 1 的柱状堆积形成中的重要作用。
