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

Six triarylamine derivatives <bold>1</bold>-<bold>6</bold> 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 <bold>1</bold>, CN for <bold>2</bold>, Cl for <bold>3</bold>, <italic>p</italic>-C₆H₄OMe for <bold>4</bold>, OMe for <bold>5</bold>, and NMe₂ for <bold>6</bold>, 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 <bold>1</bold>-<bold>6</bold>. The emission properties of these compounds were examined in different solvents (toluene, CH₂Cl₂, acetone, tetrahydrofuran (THF), and <italic>N</italic>,<italic>N</italic>-dimethylformamide (DMF)) and in solid states. Distinct dual emissions from the localized emissive state and the intramolecular charge transfer state were observed for compound <bold>5</bold> in CH₂Cl₂. Compounds <bold>1</bold> and <bold>6</bold> 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. [ABSTRACT FROM AUTHOR]