4-NR2-appended salen–indium complexes were prepared via a one-pot synthetic pathway. The complexes exhibited narrow-bandwidth red emissions with high photoluminescence quantum yields that are the highest among the reported salen-based luminophores.

A series of planarized B,N‐diarylated dibenzoazaborine compounds (5a–5e) in which various functional groups are introduced into the B‐Ph and N‐Ph moieties of nonsubstituted dibenzoazaborine compound (I) were prepared. All compounds exhibit strong low‐energy absorptions at ca. 410–426 nm with a gradual red‐shift depending on the electron‐accepting property of the four substituents (4‐R = 4‐Ph < 4‐Pm < 4‐CNPh <4‐CN) on the B‐Ph ring in 5a–5d. Introduction of an electron‐donating tBu group into the N‐Ph ring further shifts slightly the absorption band toward a lower‐energy region (5e). Importantly, all compounds undergo gradual red‐shifts in the emission leading to deep blue fluorescence for CN‐substituted 5d and 5e. Furthermore, the emissions have narrow full width at half maximum values of ca. 30 nm, high photoluminescence quantum yields (ΦPL ≈ 100%), and small Stokes shifts (11–16 nm). The electrochemical and theoretical studies further support the bandgap control and photophysical properties of compounds.

Designing multi‐resonance (MR) emitters that can simultaneously achieve narrowband emission and suppressed intermolecular interactions is challenging for realizing high color purity and stable blue organic light‐emitting diodes (OLEDs). Herein, a sterically shielded yet extremely rigid emitter based on a triptycene‐fused B,N core (Tp‐DABNA) is proposed to address the issue. Tp‐DABNA exhibits intense deep blue emissions with a narrow full width at half maximum (FWHM) and a high horizontal transition dipole ratio, superior to the well‐known bulky emitter, t‐DABNA. The rigid MR skeleton of Tp‐DABNA suppresses structural relaxation in the excited state, with reduced contributions from the medium‐ and high‐frequency vibrational modes to spectral broadening. The hyperfluorescence (HF) film composed of a sensitizer and Tp‐DABNA shows reduced Dexter energy transfer compared to those of t‐DABNA and DABNA‐1. Notably, deep blue TADF‐OLEDs with the Tp‐DABNA emitter display higher external quantum efficiencies (EQEmax=24.8 %) and narrower FWHMs (≤26 nm) than t‐DABNA‐based OLEDs (EQEmax=19.8 %). The HF‐OLEDs based on the Tp‐DABNA emitter further demonstrate improved performance with an EQEmax of 28.7 % and mitigated efficiency roll‐offs.

Deep-red (DR)-to-near-infrared (NIR) phosphorescent organic light-emitting diodes (OLEDs) have potentials for application in various fields ranging from phototherapy to sensing. Accordingly, herein, phenylpyridazinebased bidentate ligands are synthesized and subsequently utilized for the preparation of dinuclear Pt(II) complexes (1-6). The molecular structures of 1-3 is investigated by single-crystal X-ray diffraction, and the results suggest that these complexes have substantially shortened Pt•••Pt distances (2.906-2.911 Å). Complexes 1-6 exhibit intense emissions in the NIR region (700-726 nm), high photoluminescence quantum yield (PLQY) (0.11-0.18), and short phosphorescence decay lifetimes (τ = 0.64-0.95 µs) in a CH 2 Cl 2 solution. To examine the effect of N-substitution on the dinuclear Pt complexes, the phenylpyrimidine-based Pt(II) emitters 7 and 8 are prepared and discovered to have Pt•••Pt distances of 2.933 Å. 7 and 8 demonstrate strong emissions in the 628-650 nm range with high PLQY of 0.52-0.65. Theoretical studies indicate that the functional groups or atoms in the ligands play crucial roles in the formation of emitters with significantly shortened Pt•••Pt distances. 3 and 7 are employed as non-doped emitters to fabricate NIR OLEDs, and the resulting OLEDs exhibit electroluminescence peaks at 754 and 692 nm with maximum external quantum efficiencies of 3.0 and 4.4%, respectively.

We report the impact of boron acceptors on the thermally activated delayed fluorescence (TADF) properties of ortho -donor-appended triarylboron compounds. Different boryl acceptor moieties, such as 9-boraanthryl ( 1 ), 10 H -phenoxaboryl ( 2 ), and dimesitylboryl (BMes 2 , 3 ) groups have been introduced into an ortho donor (D)–acceptor (A) backbone structure containing a 9,9-diphenylacridine (DPAC) donor. X-ray crystal diffraction and NMR spectroscopy evidence the presence of steric congestion around the boron atom along with a highly twisted D–A structure. A short contact of 2.906 Å between the N and B atoms, which is indicative of an N → B nonbonding electronic interaction, is observed in the crystal structure of 2 . All compounds are highly emissive (PLQYs = 90–99%) and display strong TADF properties in both solution and solid state. The fluorescence bands of cyclic boryl-containing 1 and 2 are substantially blue-shifted compared to that of BMes 2 -containing 3 . In particular, the PL emission bandwidths of 1 and 2 are narrower than that of 3 . High-efficiency TADF-OLEDs are realized using 1 – 3 as emitters. Among them, the devices based on the cyclic boryl emitters exhibit pure blue electroluminescence (EL) and narrower EL bands than the device with 3 . Furthermore, the device fabricated with emitter 1 achieves a high external quantum efficiency of 25.8%.

The incorporation of a naphthyl ring into the azaborine core led to blue to sky-blue fluorescence with unitary photoluminescence quantum yields, narrow full width at half maximum values, and small Stokes shifts.

These authors contributed equally to this work.We report the synthesis and thermally activated delayed fluorescent (TADF) properties of ortho-carbazole-appended triazine compounds. Two donor (D)-acceptor (A) compounds, CzMeoTRZ (1) and BuCzMeoTRZ (2), in which the carbazole (Cz and t-BuCz) donor and 4,6-dipheny-1,3,5-triazine (TRZ) acceptor moieties are linked in the ortho position of the 3-methylphenylene ring were prepared and characterized. Both compounds exhibit broad blue emission at 465 and 487 nm, respectively (photoluminescence quantum yield, Φ PL = 27% and 49% in toluene), which is typical of the donor to acceptor ICT transition. The transient PL decay measurements confirm that both compounds have TADF character with the microsecond-range delayed lifetimes (τ d = 1.09 μs for 1 and 1.51 μs for 2). Electrochemical analysis indicates that both compounds undergo carbazole-centered oxidation and triazine-centered reduction. Theoretical studies further show the twisted D-A structure, effective separation of highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO), and small energy splitting between the excited singlet and triplet states for 1 and 2, all of which support the observed TADF.

A series of 4-NEt 2 -appended salenÀindium complexes bridged by different diimine units (ethylene [Et, 1], phenylene [Ph, 2], and benzonitrile [PhCN,3]) with different electronic effects were prepared in high yields by a one-pot synthetic procedure. Among them, the solid-state structure of 1 was identified by X-ray crystallography, featuring a square-pyramidal structure around the indium center. Ultraviolet-visible (UV/Vis) absorption and emission spectra of 1-3 showed typical ππ* electronic transitions centered on the salen ligands, which underwent gradual redshifts as the electron-withdrawing ability of the bridging units increased. Such bathochromic shifts resulted from lowering the energy levels of the lowest unoccupied molecular orbital (LUMO). In addition, the full width at half maxima for the emissions of 1-4 gradually decreased with increasing electron-accepting property of the bridging units. The observed photophysical properties were further supported by theoretical calculations.