The molecule is a bicyclic system (phthalazine) that bears a single substituent.

Phthalazine is defined as a benzene ring fused to a pyridazine ring (a six-membered aromatic ring with two adjacent nitrogens). The fusion occurs at the two ring junction carbons that are not adjacent to the nitrogens of the pyridazine.

On the pyridazine portion, one of the carbons adjacent to a fusion junction carries the only substituent: an exocyclic dimethylamino group. In detail, this carbon is bonded to a nitrogen atom, and that nitrogen is further bonded to two methyl groups (-N(CH3)2).