Derivatives of diazene (diimide),
HN=NH, wherein both hydrogens are substituted by hydrocarbyl groups, e.g.
PhN=NPh azobenzene or diphenyldiazene.
Source:
PAC, 1995, 67, 1307. 'Glossary of class names of organic compounds and reactivity intermediates based on structure (IUPAC Recommendations 1995)' on page 1321 (https://doi.org/10.1351/pac199567081307)