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:

Self-healing polymer coatings based on crosslinked metallosupramolecular copolymers. Self-healing coating based on metallopolymers are prepared and fully characterized. Iron bisterpyridine complexes are incorporated into a polymer network based on methacrylates, resulting in self-healing properties of these materials. Moreover, the influence of the comonomers on the thermal properties is studied in detail.
{"Chemical": ["Iron bisterpyridine", "methacrylates"]}