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:

Platinum(II) complexes with mono-aminophosphonate ester targeting group that induce apoptosis through G1 cell-cycle arrest: Synthesis, crystal structure and antitumour activity. Six new platinum(II) complexes with mono-aminophosphonate ester were synthesized and characterized by elemental analysis, (1)H NMR, ESI-MS as well as single crystal X-ray diffraction analysis. They are mononuclear structures. In all the crystal structures of complexes 1-6, the platinum centre adopts an approximately square-planar geometry, which were found to possess excellent solubility in both organic solvents and water and exhibit considerable cytotoxicity against MG-63, SK-OV-3 and HepG2 cell lines, but low cytotoxicity towards normal human liver cell HL-7702. In contrast to cisplatin, their antitumour activities are achieved through the induction of cell apoptosis by G1 cell-cycle arrest.
{"Chemical": ["platinum(II)", "Platinum(II)", "(1)H", "cisplatin", "platinum", "mono-aminophosphonate ester"]}