title: Remote impacts of methyl substituents on the guest-binding ability of self-assembled cages.
abstract: We synthesized self-assembled coordination cages in which 1,10-phenanthroline derivatives serve as capping ligands. Substituents at the 2,9-positions of the phenanthroline ligand covered the outside of the cage but had an impact on the guest binding inside the cage. Introduction of methyl groups at the 2,9-positions allowed the cage to accommodate tetraphenylsilane. Bulky mesityl groups overhanging the cage framework significantly shrunk the cage cavity through π-π interactions with the aromatic panels of the cage. The p-methyl group of the mesityl substituent was a determinant of the restricted motion of 4,4'-dimethoxybenzil inside the cage at high temperature. Thus, the presence or absence of one methyl group, which is far from the guest-binding site, makes a significant difference in the guest species and motions inside the cage.
authors.affiliation: Department of Applied Chemistry, School of Engineering, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8656 (Japan), Fax: (+81) 3-5841-7257.
authors.forename: Yu
authors.initials: Y
authors.lastname: Fang
authors.forename: Takashi
authors.initials: T
authors.lastname: Murase
authors.forename: Makoto
authors.initials: M
authors.lastname: Fujita
mesh_terms: D018360:Crystallography, X-Ray; D008024:Ligands; D008958:Models, Molecular; D015394:Molecular Structure; D010618:Phenanthrolines / Q000737:chemistry*
chemical_list: D008024:Ligands; D010618:Phenanthrolines; C025205:1,10-phenanthroline
keywords: host-guest systems; ligand effects; molecular recognition; self-assembly; through-space interactions