title: Relation between photochromic properties and molecular structures in salicylideneaniline crystals.
abstract: The crystal structures of the salicylideneaniline derivatives N-salicylidene-4-tert-butyl-aniline (1), N-3,5-di-tert-butyl-salicylidene-3-methoxyaniline (2), N-3,5-di-tert-butyl-salicylidene-3-bromoaniline (3), N-3,5-di-tert-butyl-salicylidene-3-chloroaniline (4), N-3,5-di-tert-butyl-salicylidene-4-bromoaniline (5), N-3,5-di-tert-butyl-salicylidene-aniline (6), N-3,5-di-tert-butyl-salicylidene-4-carboxyaniline (7) and N-salicylidene-2-chloroaniline (8) were analyzed by X-ray diffraction analysis at ambient temperature to investigate the relationship between their photochromic properties and molecular structures. A clear correlation between photochromism and the dihedral angle of the two benzene rings in the salicylideneaniline derivatives was observed. Crystals with dihedral angles less than 20° were non-photochromic, whereas those with dihedral angles greater than 30° were photochromic. Crystals with dihedral angles between 20 and 30° could be either photochromic or non-photochromic. Inhibition of the pedal motion by intra- or intermolecular steric hindrance, however, can result in non-photochromic behaviour even if the dihedral angle is larger than 30°.
authors.affiliation: Department of Chemistry and Material Science, Tokyo Institute of Technology, Meguro-ku, Tokyo, Japan. johmoto@chem.titech.ac.jp
authors.forename: Kohei
authors.initials: K
authors.lastname: Johmoto
authors.forename: Takashi
authors.initials: T
authors.lastname: Ishida
authors.forename: Akiko
authors.initials: A
authors.lastname: Sekine
authors.forename: Hidehiro
authors.initials: H
authors.lastname: Uekusa
authors.forename: Yuji
authors.initials: Y
authors.lastname: Ohashi