Triarylamines with branched multi-pyridine groups: modulation of emission properties by structural variation,solvents, and tris(pentafluorophenyl)borane

Six triarylamine derivatives 1–6 with branched multi-pyridine substituents were prepared and characterized. These compounds are distinguished by the substituent on one of the phenyl group with NO₂ for 1, CN for 2, Cl for 3, p-C₆H₄OMe for 4, OMe for 5, and NMe₂ for 6, respectively. As revealed by single crystal X-ray analysis, these substituents play an important role in determining the configuration of the triarylamine framework and the crystal packing of 1–6. The emission properties of these compounds were examined in different solvents (toluene, CH₂Cl₂, acetone, tetrahydrofuran (THF), and N,N-dimethylformamide (DMF)) and in solid states. Distinct dual emissions from the localized emissive state and the intramolecular charge transfer state were observed for compound 5 in CH₂Cl₂. Compounds 1 and 6 show apparent aggregated enhanced emissions in acetone/H₂O. The emission properties of these compounds were further modulated by the addition of tris(pentafluorophenyl)borane. In addition, density functional theory (DFT) and time-dependent DFT (TDDFT) calculations have been performed on the ground and singlet excited states to complement the experimental findings.