Near-infrared aggregation-induced emission characteristics of new o-carborane fluorophores with large stokes shifts and self-recovering mechanochromic luminescence†

Abstract

Solid-state near-infrared (NIR) luminescence fluorophores have attracted much attention due to their potential in bio applications and advanced optical devices. Therefore, it is essential to design and synthesize novel NIR AIE fluorophores and investigate their structure–activity relationships for applications. Here, we synthesized two NIR AIE o-carborane fluorophores with donor–acceptor–donor (D–A–D) structures. These fluorophores have emissions extending into the NIR region and are named CPO and CPS with phenoxazine (PXZ) and phenothiazine (PTZ) derivatives as the electron donors, respectively. Despite the very similar chemical structures of PXZ and PTZ, CPO and CPS exhibited rather different photophysical properties. The o-carborane fluorophores CPO and CPS show large Stokes shifts (>14 000 cm⁻¹), near-infrared AIE characteristics, and self-recovering mechanochromic luminescence. The reorganization of the molecular structures in the excited state leads to the planarization of their conjugated backbones and enhances the Stokes shifts. This work not only demonstrates an efficient strategy for constructing organic NIR AIE o-carborane-containing fluorophores, but also indicates their promising potential as advanced optoelectronic materials.