Insights into the Optical Properties of Triarylboranes with Strongly Electron‐Accepting Bis(fluoromesityl)boryl Groups: when Theory Meets Experiment

Abstract

The photophysical properties (absorption, fluorescence and phosphorescence) of a series of triarylboranes of the form 4‐D−C6H4−B(Ar)2 (D=tBu or NPh2; Ar=mesityl (Mes) or 2,4,6‐tris(trifluoromethylphenyl (Fmes)) were analyzed theoretically using state‐of‐the‐art DFT and TD‐DFT methods. Simulated emission spectra and computed decay rate constants are in very good agreement with the experimental data. Unrestricted electronic computations including vibronic contributions explain the unusual optical behavior of 4‐tBu−C6H4−B(Fmes)2 2, which shows both fluorescence and phosphorescence at nearly identical energies (at 77 K in a frozen glass). Analysis of the main normal modes responsible for the phosphorescence vibrational fine structure indicates that the bulky tert‐butyl group tethered to the phenyl ring is strongly involved. Interestingly, in THF solvent, the computed energies of the singlet and triplet excited states are very similar for compound 2 only, which may explain why 2 shows phosphorescence in contrast to the other members of the series.

Electronically Driven Regioselective Iridium‐Catalyzed C−H Borylation of Donor‐π‐Acceptor Chromophores Containing Triarylboron Acceptors

“…As such, the transition can be classified as a charge transfer (CT) transition. Similar observations were made for our previously reported D ‐π‐A systems with B( F Xyl) 2 , B( F Mes) 2 or BMes 2 as the acceptor . In accordance with a CT transition, the emission maximum of 1 shifts bathochromically with increasing solvent polarity ( λ max, em =484, 532, and 590 nm in hexane, toluene and THF, respectively).…”

Tailored Triarylborane Polymers as Supported Catalysts and Luminescent Materials

“…54 While most studies have focused on Mes 2 B groups as acceptors, Marder and co-workers found that the much enhanced acceptor strength of (FMes) 2 B (FMes = 2,4,6-tris(trifluoromethyl)phenyl) derivatives can be beneficial for optoelectronic application. 55,59 These findings prompted us to investigate the photophysical properties of our polymers and model compounds in more detail.…”

Chemical Regulation of Fluorescence Lifetime

“…Triphenylamines possessed a characteristic propeller-like structure and were frequently employed in the construction of AIE fluorophores. 28 Lu and co-workers designed a series of phenylmethylene pyridineacetonitrile derivatives bearing a triphenylamine (TPA) structure and pyridine ring with the nitrogen atom at the ortho (36), meta (37), and para (38) position in Figure 5c. 29 In tetrahydrofuran (THF), their fluorescence lifetimes were only approximately 1 ns, but in the solid state, these lifetimes were significantly extended.…”

“…This conjugated structure facilitated efficient electron transfer within the molecule, leading to reduced nonradiative energy loss and, consequently, longer fluorescence lifetimes. Halet and co-workers performed DFT and time-dependent (TD) DFT calculations to investigate the photophysical properties of a series of triarylborane derivatives 52 – 54 (Figure a, 52–54) …”