[{"from": "human", "value": "Synthesize a molecule that matches the given characteristics. The molecule is a divalent inorganic anion obtained by removal of both protons from diphosphonic acid. It is a phosphorus oxoanion and a divalent inorganic anion. It is a conjugate base of a diphosphonate(1-)."}, {"from": "gpt", "value": "[O][=P][=Branch1][C][=O][O][P][=Branch1][C][=O][=O]"}]