The crystal structures reported her

The crystal structures reported herein are based on entries in theCambridge Structural Database (www.ccdc.cam.ac.uk) as of August2017. Chalcones and their derivatives are an uncommon exampleof naturally occurring three-carbon a,b-unsaturated carbonylligands, which can act as chelating agents toward a variety of metals to form stable complexes. Besides reporting the synthesis,existing structures and characterization of metal chalcone complexes with a focus on coordination chemistry, an outline of thereported application studies on their bioactivity is given.In general, the biological studies of metal chalcone complexesare relatively scarce and incoherent. Still, the preparation of a considerable number of metal chalcone complexes was motivated bythe hope to synergize the reported bioactivities, e.g. cytotoxicproperties of anti-tumor-acting chalcones [44–46], with the biological activity of some metal ions. Therefore, besides the challenging chemistry, new coordination compounds are desirable toexplore if the compound of a specific metal with a chalcone wouldbe more bioactive than the pure chalcone ligand. In the last decades chalcones have been subject to numerous metal coordinationreactions in order to synthesize stable coordination compounds.Some reviews about metal complexes of general flavonoids, likeflavones or flavonoid-related chromone, exist, addressing differentsynthetic approaches, properties, biological and therapeutic applications [47,48], while a specific record on the synthesis and significance of metal complexes of chalcones is missing. Bysystematically covering the reported biological application studiesof metal chalcone compounds, this survey is expected to help inidentifying crucial molecular properties to be further developedor applied to other molecular scaffolds in order to enhance distinctbioactivities. As a combination of complex stability, electronicstructure and complex geometry/polarity, the potential biologicalactivity of metal chalcone complexes is inherently connected tothe peculiar coordination chemistry of chalcones.