NEW MATERIAL:The compound of formula (X is nitro, carboxyl or cyano; Y is 7W17C alkyl; Z is H or 7W17C alkyl).

EXAMPLE: N-Heptyl-4-[4-nitrophenyl]azobenzeneamine.

USE: An organic optical material. It has non-linear optical effect and forms a monomolecular film having oriented molecules.

PREPARATION: p-Nitroaniline or p-aminobenzoic acid is dissolved in dilute hydrochloric acid under heating, cooled to obtain a hydrochloride, and added with sodium nitrite dropwise under cooling to obtain diazonium salt. An N-alkyl- substituted aniline is dissolved in an organic solvent containing suspended sodium acetate to prevent the ionization of the amino group, cooled, and made to react with the diazonium salt by adding the aqueous solution of the salt dropwise to obtain the compound of formula.