[{"from": "human", "value": "Synthesize a molecule that matches the given characteristics. The molecule appears as a colorless crystalline solid. Denser than water. Toxic by inhalation and ingestion. Produces toxic oxides of nitrogen during combustion."}, {"from": "gpt", "value": "[C][#Branch1][C][#N][Hg-2][Branch1][Ring1][C][#N][Branch1][Ring1][C][#N][C][#N].[K+1].[K+1]"}]