Photophysical properties and color-tunability of diaryl ether-bridged pyrrolo[3,2-b]pyrrole (TAPP) derivatives

Diaryl ether-bridged pyrrolo[3,2-b]pyrrole (DHPP) derivatives were synthesized, and their photophysical properties were systematically investigated in both solution and solid states. UV-vis spectroscopy in toluene, THF, and DMSO revealed characteristic pi ->pi & lowast; absorption bands around 350-360 nm for all compounds, showing minimal solvent dependence. Fluorescence measurements indicated emissions around 430 nm in nonpolar and moderately polar solvents (toluene, THF), whereas highly polar DMSO induced pronounced bathochromic shifts (470-500 nm) for ortho-chlorinated derivatives (2-Cl (6), 2,4-diCl (10), and 2,5-diCl (11)). These shifts are attributed to enhanced stabilization of the intramolecular charge transfer (ICT) state due to increased excited-state dipole moments and specific solvation effects in DMSO. Solid-state photoluminescence (PL) studies showed similar to 25 nm red shifts for the same derivatives, while other derivatives-maintained emissions near 450 nm, highlighting the effect of substituent position on excited-state conformation and electron density. CIE color coordinate analysis confirmed solvent- and substituent-dependent emission tunability, indicating potential applications as solid-state, color-tunable luminescent materials. Overall, the results demonstrate the crucial role of the diaryl ether bridge in modulating electronic communication and controlling aggregation-induced quenching, as well as the impact of substituent positioning on fine-tuning photophysical properties for advanced optoelectronic applications.