title: Self-Assembly of 4-(Diethylboryl)pyridine: Crystal Structures of the Cyclic Pentamer and Hexamer and Their Solvent-Dependent Selective Crystallization.
abstract: Two distinct oligomeric structures were obtained by the self-assembly of 4-(diethylboryl)pyridine (1). In the (1)H NMR spectrum of 1 in CDCl3, at least two sets of signals were observed for the pyridyl α- and β-hydrogen atoms. ESI-MS, VPO, and TLC analysis revealed that 1 assembles mainly into a mixture of cyclic pentamers and hexamers in solution via intermolecular boron-nitrogen coordination bonds. Crystallization of 1 in THF by vapor diffusion of EtOH or in CHCl3 afforded the cyclic hexamer incorporating one THF molecule (16·THF) or 1.5 mol equiv of chloroform molecule (16·CHCl3), respectively. Similarly, a solution of 1 in a mixture of benzene and hexane furnished the cyclic pentamer bearing two benzene molecules (15·C6H6). It seems that the solvent differences affected the crystallization of the two distinct cyclic oligomers of 1, either of which was cocrystallized predominantly with the solvent molecule. Thermogravimetric analysis of the crystals and NMR studies of the solution revealed that the noncovalent interactions between the host and guest are not strong enough to hold the guest molecule in the cavity.
authors.affiliation: Department of Clinical Nutrition, Faculty of Health Science, Suzuka University of Medical Science , Suzuka, Mie 510-0293, Japan.
authors.forename: Shigeharu
authors.initials: S
authors.lastname: Wakabayashi
authors.affiliation: Department of Clinical Nutrition, Faculty of Health Science, Suzuka University of Medical Science , Suzuka, Mie 510-0293, Japan.
authors.forename: Yuka
authors.initials: Y
authors.lastname: Hori
authors.affiliation: Department of Pharmaceutical Sciences, Faculty of Pharmaceutical Sciences, Suzuka University of Medical Science , Suzuka, Mie 513-8670, Japan.
authors.forename: Seiji
authors.initials: S
authors.lastname: Komeda
authors.affiliation: Department of Chemistry, Graduate School of Science, Nagoya University , Furo-cho, Chikusa-ku, Nagoya 464-8602, Japan.
authors.forename: Yuki
authors.initials: Y
authors.lastname: Shimizu
authors.affiliation: Department of Chemistry, Graduate School of Science, Nagoya University , Furo-cho, Chikusa-ku, Nagoya 464-8602, Japan.
authors.forename: Yasuhiro
authors.initials: Y
authors.lastname: Ohki
authors.affiliation: Division of Chemistry for Materials, Graduate School of Engineering, Mie University , Tsu, Mie 514-8507, Japan.
authors.forename: Misaki
authors.initials: M
authors.lastname: Horiuchi
authors.affiliation: Division of Chemistry for Materials, Graduate School of Engineering, Mie University , Tsu, Mie 514-8507, Japan.
authors.forename: Takahito
authors.initials: T
authors.lastname: Itoh
authors.affiliation: Department of Chemistry, Faculty of Science, Yamaguchi University , Yamaguchi 753-8512, Japan.
authors.forename: Yoshikazu
authors.initials: Y
authors.lastname: Sugihara
authors.affiliation: Research Center for Materials Science, Nagoya University , Furo-cho, Chikusa-ku, Nagoya 464-8602, Japan.
authors.forename: Kazuyuki
authors.initials: K
authors.lastname: Tatsumi