Synthesis and Characterization of New o-Carboranes-Based Aggregation-Induced Emission Molecules with Ultra-Large Stokes Shift

Four o-carborane-based aggregation-induced emission molecules with ultra-large Stokes shifts were designed and synthesized. To explore the origin of the ultra-large Stokes shifts (Delta lambda approximate to 268-294 nm) of the four target molecules, a new molecule named CZ-Ph-PO was synthesized by replacing the o-carborane unit in CZ-CB-PO with a benzene ring. It was found that the ultra-large Stokes shift was the result of the combined action of diphenylphosphinyl and o-carborane, in which o-carborane was the key group. In addition, combined with the single crystal structure analysis, the effect of halogens on molecular photophysical properties was investigated. Our work provides a reference for the design and synthesis of o-carborane-based fluorescent molecules with ultra-large Stokes shifts.