Unusual reaction of (E)-2-[(benzo[d]thiazol-2-ylimino)methyl]-5-(diethylamino)phenol with triphenylborane: crystal structures and optical properties

Abstract

The molecular and crystal structure of (E)-2-[(benzo[d]thiazol-2-ylimino)methyl]-5-(diethylamino)phenol (C18H19N3O2S, Et2N-Bz) and its unexpected reaction product with triphenylborane, 2,2-diphenyl-1,3-dioxa-2-borata-1,2-dihydronaphthalene [systematic name: N,N-diethyl-2,2-diphenyl-2H-1,3λ3,2λ4-benzodioxaborinin-7-amine, C23H24BNO2, (I)] are described. For Et2N-Bz, the hydroxyl group is involved in an intramolecular hydrogen bond with the imino nitrogen atom and the C=N bond displays an E configuration. The crystal packing is characterized by layers of inversion dimers parallel to the (10\overline{1}) plane and chains of molecule in the a-axis direction formed through C—H...O interactions. Complex (I) crystallizes with two molecules (A and B) in the asymmetric unit, which differ in the orientation of the ethyl groups. The 1,3-dioxa-2-borata-1,2,3,4-tetrahydronaphthalene ring displays a slight envelope conformation with the boron atom as the flap. In the crystal packing, chains of alternating A and B molecules formed by C—H...O hydrogen bonds run in the b-axis direction. The UV–vis absorption and emission properties of the compounds are discussed and their aggregation-induced emission properties are further investigated.

Keywords

• crystal structure
• benzothiazole
• boranils
• fluorescence
• aggregation-induced emission