Herein, the design,s ynthesis, optical properties, and mechanofluorochromism characteristics of as eries of conjugates having covalently linked triarylborane (TAB) and anil/boranil units (TAB-anil: 1a-3a and TAB-boranil: 1-3)a re reported. The electronic interactions between TABa nd anil/ boranili n1a-3a and 1-3 were fine-tuned by changing the boryl moiety's positiono nt he phenyls pacer connecting the BMes 2 (Mes = mesityl)a nd anil/boranil units.Ab oryl moiety at the meta position(1a)o ft he phenyl spacers tabilizest he enolic form (E-OH), whereas ab oryl moiety at the para position (2a and 3a)s tabilizes the keto form (Z-NH) in the solid state.H owever,i ns olution 1a, 2a,a nd 3a exhibit keto-enol tautomerism in both ground and excited states.C ompounds 1a-3a and 1-3 show red-shifted absorption compared with 4a and 4,which are devoid of TABmoieties, which indicate effectivep articipation of an empty po rbital on the boronc enteri n1a-3a and 1-3.C ompounds 1 and 2 showed fluorescence variations in response to externals timuli such as mechanical grinding. Long phosphorescence lifetimes of 18-46 ms were observed for compounds 1-3.T he observed optical properties of 1a-3a and 1-3 are rationalized in the context of quantumm echanical calculations.

We studied the dual emission characteristics of a series of boryl-BODIPYs (1−6) comprised of triarylborane (TAB) as an energy donor and BODIPY as an energy acceptor. The molecular conformations of dyads 1−6 were systematically tuned by judiciously changing the spacer that bridged the boryl and BODIPY moieties. Frontier molecular orbitals (FMOs) are localized in 3, 4, and 6 with a twisted molecular conformation. In contrast, FMOs are significantly delocalized in 1, 2, and 5 with the least-twisted molecular conformation. Dyads 1−6 showed dual emission features when they were excited at the TAB-dominated absorption band. However, the ratio between the two emission bands in 1−6 significantly varied depending on the molecular conformations. Systematic photoluminescence (PL) studies (both steady-state and time-resolved PL) together with computational, crystal structure, and anion binding studies established that the frustrated excited-state energy transfer from borane to BODIPY is the cause of the dual emission features in these molecular dyads. These studies also revealed that the energy transfer from borane to BODIPY can be elegantly tuned by modulating the dihedral angle between these two moieties.

We report a simple and novel molecular design strategy to enhance rISC in boron-based donor-acceptor systems to achieve improved delayed fluorescence characteristics. Dianthrylboryl ((An) 2 B)-based aryl aminoboranes 1 (donor: phenothiazine) and 2 (donor: N,N-diphenylamine) were synthesized by a simple one-pot procedure. The energy of the electronic excited states in 1 and 2 were modulated by varying the arylamine donor strength and electronic coupling between D and A moieties. The presence of a large π-system (anthryl moiety) on boron enhances the electronic communication between donor arylamine and acceptor boryl moieties, and hence, both 1 and 2 exhibit delayed fluorescence characteristics in a broad range of temperatures (80-300 K). Single crystal X-ray analysis and temperature-dependent photophysical studies together with theoretical studies were carried out to rationalize the observed intriguing optical signatures of 1 and 2.

Design and development of stable blue emitters are challenging owing to their potential applications in displays and lighting technologies. Triarylborane (TAB) with suitable donors has been extensively exploited in several fields. We report herein the synthesis and structural characterization of a simple 2-(dimesitylboryl)-1H-pyrrole (2) and its precursor N-Boc-(dimesitylboryl)-pyrrole (1). In the crystal lattice of 2, supramolecular dimer was formed by strong NÀ H-π (2.59 Å) hydrogen bonding interactions between the monomers and this dimer is further connected by weak van der Waals interactions (CÀ H-π) with neighbouring dimers to form a supramolecular network. There is no solvatochromism noted in the absorption spectra, however significant positive solvatochromism was observed in the fluorescence spectra; points to the polar nature of excited state of 1 and 2. Compound 2 showed intense and efficient blue color luminescence in the solid state than that of 1. Thus, NÀ H-π interactions and π-excessive nature of pyrrole are responsible for the above features. Impressively, compounds 1 and 2 exhibit the phosphorescence emission with a long-lived lifetime of~0.55 s at 77 K and delayed fluorescence at room temperature. DFT/TD-DFT calculations were performed to support the experimental observations.

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.