You will be shown an abstract from a biomedical research paper. Given this abstract, your task is to extract all unique entities of the following types: ["Chemical"].

Please return the output as a JSON object of the format: {"Chemical": ["Arsenic", ...]}. The keys should be entity types and values should be lists of extracted entities belonging to the corresponding type. If you cannot find entities belonging to a specific type, the value should be [].

Only output the JSON object and do not include any additional text.

Abstract:

Synthesis and Biological Evaluation of [1,2,4]Triazolo[3,4-a]phthalazine and Tetrazolo[5,1-a]phthalazine Derivatives Bearing Substituted Benzylpiperazine Moieties as Positive Inotropic Agents. Two series of [1,2,4]triazolo[3,4-a]phthalazine and tetrazolo[5,1-a]phthalazine derivatives bearing substituted benzylpiperazine moieties have been synthesized and evaluated for their positive inotropic activity by measuring left atrium stroke volume on isolated rabbit heart preparations. The majority of the derivatives exhibited better in vitro activity than the existing drug, milrinone, and 6-((4-(4-methoxyphenyl)piperazin-1-yl)methyl)tetrazolo[5,1-a]phthalazine. 8 m in particular was identified as the most potent with an increased stroke volume of 12.02 ± 0.20% (milrinone: 2.46 ± 0.07%) at a concentration of 3 × 10(-5)  m. The chronotropic effects of the compounds that exhibited good potency were also evaluated.
{"Chemical": ["tetrazolo[5,1-a]phthalazine", "[1,2,4]Triazolo[3,4-a]phthalazine", "Benzylpiperazine", "milrinone", "[1,2,4]triazolo[3,4-a]phthalazine", "benzylpiperazine", "Tetrazolo[5,1-a]phthalazine", "6-((4-(4-methoxyphenyl)piperazin-1-yl)methyl)tetrazolo[5,1-a]phthalazine"]}