To obtain the subject new compound useful as an optical material exemplified by a secondary nonlinear optical material, a coloring matter, etc.

This new compound is a compound of formula I (m is 0 or 1; n is 0-2; R is a nitro-substituted aryl), e.g. β-ionylidene-2,4- dinitrophenylhydrazone. The compound of formula I is obtained by condensing a compound of formula II (e.g. β-ionone and β-ionylideneacetaldehyde) with hydrazines of the formula R-NH-NH2 (e.g. 4-nitrophenylhydrazine) in the presence of an acidic material (e.g. a mineral acid such as phosphoric acid, sulfuric acid and hydrochloric acid, an organic acid such as acetic acid, propionic acid and p-toluenesulfonic acid).