title: Molecular recognition of upper rim functionalized cavitand and its unique dimeric capsule in the solid state.
abstract: Cavitand 1 possesses four 2,2'-bipyridyl pillars on its upper rim that encapsulates small guests, such as nitromethane, acetonitrile, methyl acetate, ethyl acetate, and N-methylacetamide, into a deep cavity to form host-guest complexes in a 1:1 ratio. Nitroethane, N,N-dimethylformamide, and N,N-dimethylacetamide were not bound in this manner. A guest-binding study and molecular mechanics calculations revealed that the four 2,2'-bipyridyl pillars of cavitand 1 created a steric boundary that is responsible for selective guest recognition. In the solid state, cavitand 2 formed a unique chiral capsule 2(2) by π-π stacking interactions between the 2,2'-bipyridyl pillars. A nitromethane molecule was unusually placed deep inside the cavity, as directed by the multiple hydrogen bonding interactions between the nitromethane oxygen atoms, the C-H bonds of the bridge methylenes and the pillar phenyl groups.
authors.affiliation: Department of Chemistry, Graduate School of Science, Hiroshima University, 1-3-1 Kagamiyama, Higashi-Hiroshima, 739-8526, Japan. haino@hiroshima-u.ac.jp.
authors.forename: Mutsumi
authors.initials: M
authors.lastname: Kobayashi
authors.forename: Mei
authors.initials: M
authors.lastname: Takatsuka
authors.forename: Ryo
authors.initials: R
authors.lastname: Sekiya
authors.forename: Takeharu
authors.initials: T
authors.lastname: Haino