title: Engineering double to quintuple stacks of a polarized aromatic in confined cavities.
abstract: 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.
authors.affiliation: Department of Applied Chemistry, School of Engineering, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8656, Japan.
authors.forename: Yoshihiro
authors.initials: Y
authors.lastname: Yamauchi
authors.forename: Michito
authors.initials: M
authors.lastname: Yoshizawa
authors.forename: Munetaka
authors.initials: M
authors.lastname: Akita
authors.forename: Makoto
authors.initials: M
authors.lastname: Fujita