Liquid azo dyes

Any liquid azo dyes, in which auxochrome such as dialkylamino, alkoxy, and amino group is attached in a molecule, were produced. In a series of 2-alkyl-4'-(dimethylamino)azobenzenes, the butyl, hexyl, octyl, and dodecyl derivatives were liquid at room temperature, whereas the propyl, 1-methylethyl, 1-methylpropyl, 1,1-dimethylethyl, and octadecyl derivatives were solid. Thus, it is essential for liquid azo dyes to have a medium n-alkyl group at the 2-position. In a series of 2-butyl-4'-(dialkylamino) azobenzenes, the dimethylamino, diethylamino, dibutylamino, dioctylamino, and didodecylamino derivatives were liquid. 2-Butyl-4'-methoxyazobenzene and 4-amino-3,5-dimethy1-2'-butylazobenenzne were also liquid, whereas 2-butyl-4'-hydroxyazobenznene, 4-amino-2'-butylazobenzene, and 2-butyl-4'-(methylamino)azobenzene were solid. The prevention of pi-pi stacking, alkyl alkyl interactions, and intermolecular hydrogen bond could produce liquid azo dyes. (c) 2015 Elsevier Ltd. All rights reserved.