Charge–Transfer Complexes and Fluorescence Modulation in Amide- and Carboxy-Substituted 2-Phenyl-1,3,2-benzodiazaboroles

High Resolution Image Download MS PowerPoint Slide A library of amide- and carboxy- functionalized 2-phenyl-1,3,2-benzodiazaborole derivatives was synthesized via microwave-assisted cyclic condensation to explore the effects of pseudoaromaticity on charge-transfer complex (CTC) formation and photophysical behavior. All compounds were characterized by NMR, IR, UV–vis, and fluorescence spectroscopy. While absorbance profiles remained consistent (λ max = 298 – 324 nm), several derivatives exhibited strong bathochromic emission (λ em = 363 – 555 nm) and exceptionally large Stokes shifts (Δ v > 150 nm), particularly those bearing –OCH 3 groups. Red-shifted fluorescence and DFT calculations suggest antiparallel dimeric CTCs stabilized by B–N delocalization. These results highlight amide- and carboxy- 1,3,2-benzodiazaborole frameworks as tunable pseudoaromatic systems with potential applications in optical sensing and functional material design.