Croconic acid-based compounds: synthesis, structural characteristics, properties and applications of an intriguing class of functional organic materials

The present review springs up from the demand for an overview on the scientific advances in croconic acid-based materials and their potential technological applications. Modern technological challenges in the biomedical and energy fields share the common need for the use of environmentally friendly materials and devices that are safe for humans. Croconic acid-based compounds are an interesting class of functional organic materials of great potential since they combine intrinsic biocompatibility with chemico-physical properties that are very attractive for a number of applications, including in the bio-medical sector, i.e., theranostics; energy field, i.e., energy conversion, energy storage and energy saving; and sensing field. Despite the high potential, to date, only few reviews covering specific aspects such as synthesis or, mainly, biomedical applications are available in the literature, while reviews summarizing all investigations performed on this intriguing class of organic materials, from their design to application, are lacking. Through an overview of synthetic approaches, basic structural characteristics, chemico-physical properties and applications, the present review aims to extensively analyse the research advances and the role played by such functional organic materials, with the hope of stimulating new insights for future perspectives.