[{"from": "human", "value": "Design a molecule that meets the criteria outlined in the description. The molecule is a monocarboxylic acid anion that is the conjugate base of thiophene-2-carboxylic acid, obtained by deprotonation of the carboxy group; major species at pH 7.3. It is a conjugate base of a thiophene-2-carboxylic acid."}, {"from": "gpt", "value": "[C][=C][S][C][=Branch1][Ring2][=C][Ring1][Branch1][C][=Branch1][C][=O][O-1]"}]