This compound is a thiophene ring (a five-membered ring with one sulfur and four carbons in an aromatic arrangement) bearing a single substituent at the carbon directly adjacent to sulfur. Number the ring so that sulfur is at position 1; the substituent is therefore at position 2. This substituent is a two-carbon chain with a double bond: the first of those two carbons (the one bonded to the ring) also carries a nitro group, in which a nitrogen atom is bonded to two oxygen atoms-one via a double bond and the other via a single bond-resulting in the nitrogen carrying a positive charge and the oxygen attached via a single bond carrying a negative charge.