Molecular Persistent Room-Temperature Phosphorescence from Tetraarylaminoboranes

Abstract

Herein, we report the synthesis, molecular structure, and optical features of tetrarylaminoboranes 1 (Mes 2 B-N(Ph)(C 10 H 7 )) and 2 (Mes 2 B-N(Ph)(C 14 H 9 )). In the solution state, 1 shows aggregation-induced emission enhancement and color switching, while 2 displays emission color switching and aggregation-caused quenching. At 77 K, frozen solutions of 1 show delayed fluorescence (DF) and phosphorescence, whereas 2 display only DF. Pristine solids of 1 and 2 showed delayed fluorescence under ambient conditions; however, crystals of both compounds show no phosphorescence under similar conditions. Polymethyl methacrylate thin films of 1 (1 wt % doping concentration) exhibit persistent room-temperature phosphorescence (pRTP) lasting for ∼0.5 s. In contrast, 2 does not show phosphorescence under similar conditions. Systematic photophysical studies and theoretical (DFT and TD-DFT) calculations are performed on these molecules to rationalize their intriguing optical characteristics.

Filling the gap with a bulky diaryl boron group: fluorinated and non-fluorinated copper pyrazolates fitted with a dimesityl boron moiety on the backbone

“…13 Compound {[3,5-(CH 3 ) 2 Pz]Cu} 3 (2), involving a nonfluorinated pyrazolate, is also a photoluminescent solid but exists as discrete dimers of trimers in the solid state with relatively close (2.946 Å), inter-trimer cuprophilic interactions. 8,14 Triarylboranes containing a dimesitylboron moiety (Mes 2 B-, due to the presence of a low-lying empty p z -orbital on boron and steric bulk; Mes = 2,4,6-(CH 3 ) 3 C 6 H 2 ) are widely utilized for applications [15][16][17][18] that include the development of photo-luminescent materials, chromophores in OLEDs as well as nonlinear optical materials, [19][20][21][22][23][24] powerful Lewis acids, 19,25 isolable radicals, [26][27][28] and sensors for various analytes includ- ing fluoride and cyanide ions. 17,[29][30][31] Among these, organoboron compounds with heterocyclic linkers, such as pyridines, imidazoles, and thiophene, etc., are of significant current interest as they can enhance the electrophilicity at boron, alter luminescence properties, and provide sites for metal ion coordination.…”

Chiral B–N AIEgens: Intense Blue Circularly Polarized Luminescence and Piezochromism

“…Substitution of a B–N unit for the isosteric CC moiety in π-conjugated carbon frameworks produces materials with structural similarities but with altered optoelectronic properties and applications. − Recently, we discovered AIE in tetraarylaminoborane (TAAB), a B–N surrogate of CC analogous to tetraphenylethene (TPE), the popular AIEgen . This opened the door for developing a new class of multifunctional materials from the TAAB prototype AIEgen. − The chiroptical properties of popular prototypical TPE AIEgens are well-documented in the literature, , but the relatively new TAAB AIEgens have not been explored in developing bright chiral emitters (Figure a). We plan to integrate the chiral units with the TAAB AIEgen core to achieve bright CPL with a considerable dissymmetry factor in the solid state.…”