Scalable Solvent-Free Synthesis of a Linear Heteroaromatic Trimer with Crystallization-Induced Room-Temperature Phosphorescence

The polymerization mechanism and key oligomer intermediates during thermal condensation of benzoguanamine (BG) are unclear. Herein, we report a mixed thermal condensation strategy using BG and pre-synthesized dimer to produce the trimer (BG)₃ with significantly enhanced yield. Comprehensive characterizations confirm its linear structure. (BG)₃ exhibits a high molar absorption coefficient, approximately double the dimer and quadruple the monomer. Crucially, it displays crystallization-induced room-temperature phosphorescence (CIRTP) with a lifetime of 514.9 µs in the crystalline state.