Donor Engineering Meets Main‐Group Organometallic Interplay: Carbazole Versus Anthracene in Cyanostilbene–Borane Solid‐State Emitters

ABSTRACT We present a comparative investigation of two main‐group organoboron donor–acceptor (D–A) luminophores, carbazole‐cyanostilbene‐duryl‐bridged dimesitylborane (CZ‐CS‐TAB) and anthracene‐cyanostilbene‐duryl‐bridged dimesitylborane (AN‐CS‐TAB) , to elucidate the influence of donor identity and molecular connectivity on their photophysical behavior in solution as well as solid‐state. Both compounds were synthesized via stepwise Knoevenagel condensation followed by Suzuki–Miyaura coupling and characterized comprehensively by multi nuclear NMR, and HRMS spectroscopy. In solution state, CZ‐CS‐TAB exhibits hybridized local charge transfer (HLCT) excited state with moderate solvatochromism (440–475 nm), while AN‐CS‐wTAB displays only locally excited (LE) emission with minor solvatochromic response. Both systems demonstrate typical aggregation‐induced emission (AIE) and solid‐state emissive characteristics, accompanied by mechanochromic fluorescence (MFC) behavior. Mechanical grinding induces a reversible blue‐to‐cyan shift (460→495 nm→480 nm) in CZ‐CS‐TAB and a small red shift (530→540→535 nm) in AN‐CS‐TAB , correlating with a crystalline‐to‐amorphous transformation confirmed by PXRD. DFT and TD‐DFT analyses support the donor‐dependent HLCT and LE excited states, rationalizing the observed emission features. Both luminophores exhibit excellent thermal stability ( T d ≈ 350 °C). This study highlights how donor engineering coupled with borane acceptor frameworks enables systematic modulation of emissive, AIE, and mechanochromic properties, offering design strategies for multifunctional main‐group organometallic luminophores.