Luminescent halogen clusters

Halogen···halogen (X···X) short contacts, especially halogen bonds (XBs), have been widely used in multifarious fields because of their bridging function among luminophores, as well as their well-known heavy atom effect. Little attention, however, has been paid to the luminescent ability of halogen clusters. It remains unknown whether they could be emissive. Herein, to our knowledge, we report the first examples of emissive halogen clusters with fluorescence-phosphorescence dual emission in an aggregated state and even under ambient conditions, which should be attributed to the extended delocalization through effective intra- and intermolecular X···X contacts. Additionally, multi-tunable luminescence in response to excitation wavelength, temperature, and compression is noticed. These results unveil the potential of halogen clusters as novel chromophores and may inspire further exploration of nonconventional luminophores involving halogen moieties.