Multifunctional luminescent molecules of o-carborane-pyrene dyad/triad: flexible synthesis and study of the photophysical properties

The development of organic single-molecule multiple photoluminescence compounds hold a great promise for advanced opt-electronic devices, optical probes and temperature sensors. The pyrenyl-substituted o-carborane, CSP and CDP, were obtained via a modified nickel-catalyzed cross-coupling reaction in satisfactory yields. Based on variety of spectroscopic measurements, it was found that the CSP and CDP exhibit multifunctional luminescent properties, such as dual emissions as well as thermochromic luminescence between orange and blue for CSP, ternary species emissions for CDP, and aggregation induced emission (AIE) and AIE enhancements (AIEE) properties for both. The origination of the multiple photoluminescence attributes was investigated deeply. We demonstrated that the multiple photoluminescence in the pyrenyl-substituted o-carborane rose from the electronic interaction between pyrenyl and o-carboranyl leading to the formation of ICT state, and the mono-molecular excimer emission attributed to the interaction between the conformational of two face- to-face pyrene chromophores. In addition, clear thermochromic luminescence properties were caused by ICT at room temperature and excimer formation at 77 K in the solid state. The results are useful as a guideline for designing luminescent solid materials with multiple photoluminescence and thermochromic luminescence properties.