Activation of room temperature phosphorescence of organic co-crystals. A novel approach based on Halogen-Bond

There are only few works concerning room temperature phosphorescence of metal-free organic crystals. This is essentially due to the spin forbiddingness of the intersystem crossing process and to structural and energetic constraints typical of solid state. In order to obtain phosphorescence from purely organic compounds,1-8 Naphthalenimides are good candidates for, at least, two reasons:in aromatic carbonyls the triplet state generation is efficient and this kind of imides are easy-to-synthesize cheap building-blocks for co-crystals. In this study halogens are not used only as a "glue", but also they play the role of heavy-atoms to induce spin-orbit coupling of in the aromatic compounds. This effect allows the control of optical properties. The final target of the work is the achievement of a high-quantum-yield phosphorescence at room temperature.