Salts or charge-transfer complexes of styphnic acid (2,4,6-trinitrobenzene-1,3-diol).
See: picrates
Source:
PAC, 1995, 67, 1307. 'Glossary of class names of organic compounds and reactivity intermediates based on structure (IUPAC Recommendations 1995)' on page 1367 (https://doi.org/10.1351/pac199567081307)