title: Cooperative effects of o- and m-methyl groups on the intramolecular charge-transfer emission properties of dibenzoylmethanatoboron difluorides.
abstract: The photophysical properties of o-tolyl-, m-tolyl-, and p-xylyl-substituted asymmetric diaroylmethanatoboron difluorides in a mixture of CH2Cl2and c-C6H12, and in the crystalline state were determined. In solution, the fluorescence (FL) properties of these substances are controlled by the position and number of methyl groups on the phenyl rings. An especially interesting finding is that FL from the p-xylyl derivative occurs from an excited state which possesses intramolecular charge-transfer character caused by the o- and m-methyl groups cooperatively. The results of X-ray crystallographic analysis reveal that these asymmetric diaroylmethanatoboron difluorides form dyads through orbital overlap of neighboring molecules. This phenomenon governs the unique FL properties of these substances in the solid state.
authors.affiliation: Department of Applied Chemistry, Graduate School of Engineering, Osaka Prefecture University, 1-1 Gakuen-cho, Naka-ku, Sakai, Osaka 599-8531, Japan. ikeda@chem.osakafu-u.ac.jp.
authors.forename: Mirai
authors.initials: M
authors.lastname: Tanaka
authors.forename: Shunsuke
authors.initials: S
authors.lastname: Muraoka
authors.forename: Yasunori
authors.initials: Y
authors.lastname: Matsui
authors.forename: Eisuke
authors.initials: E
authors.lastname: Ohta
authors.forename: Takuya
authors.initials: T
authors.lastname: Ogaki
authors.forename: Kazuhiko
authors.initials: K
authors.lastname: Mizuno
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Ikeda