The core is a pyridazine ring (six-membered aromatic ring with two adjacent nitrogens).

Two substituents on this ring:
- On a carbon meta to either ring nitrogen, the ring bears a cyano group (-C#N) (carbon triple-bonded to nitrogen).
- On another carbon that is ortho to a nitrogen and meta to the cyano-bearing carbon, the ring carries a thio-linked side chain: the sulfur is directly attached to the ring, and is bonded to a methine carbon that bears one methyl group and is also bonded to a carboxylic acid carbonyl.