Benzo-extended N^N^N-chelated tetracoordinate boron hetero[8]helicene featuring an inner N–B–N helical rim for circularly polarized TADF

Abstract

The synthesis of tetracoordinate boron helicenes bearing B–N units aligned along the inner rim of the helical backbone remains exceedingly rare due to steric hindrance. We present the design and synthesis, and comprehensive characterization of a novel benzo-fused N^N^N-chelated tetracoordinate boron-containing hetero[8]helicene (Hel-BNN), which exhibits a highly twisted inner N–B–N helical rim. The fused benzene rings at the termini of the tridentate N^N^N ligand impart enhanced molecular rigidity and thermal stability (T_d = 460 °C), along with tunable electronic structures with a moderate bandgap (∼2.6 eV). Density functional theory (DFT) calculations reveal a helically distorted geometry and a spatially separated frontier orbital distribution, resulting in a small singlet–triplet splitting energy (ΔE_ST = 0.22 eV) conducive to efficient thermally activated delayed fluorescence (TADF). Hel-BNN exhibits strong circular dichroism and circularly polarized luminescence (CPL), with dissymmetry factors (g_abs and g_PL) on the order of ∼10⁻³. When employed as a dopant in organic light-emitting diodes (OLEDs), Hel-BNN delivers bright yellow electroluminescence with a peak external quantum efficiency of 21.9% and distinct circularly polarized electroluminescence (CPEL) signals from resolved enantiomers. This work demonstrates the potential of benzo-fused tetracoordinate boron hetero-helicenes as promising chiral emitters for high-performance CPL-TADF optoelectronic applications.

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Guoyun Meng

Guoyun Meng obtained his PhD degree in 2020 from the Beijing Institute of Technology. From 2020 to 2022, he conducted postdoctoral research at Tsinghua University. Presently, he serves as an associate professor at the School of Chemical Science and Technology, Yunnan University. His research focuses on boron-nitrogen-embedded polycyclic aromatic multiple resonance emitters and devices.

1. Introduction

In recent years, chirality has emerged as a central focus in the research of π-extended polycyclic aromatic hydrocarbons (PAHs).¹ The rapid advancement of synthetic methodologies for polycyclic heteroaromatic systems and extended nanographenes has facilitated the construction of diverse PAH derivatives featuring curved or non-planar geometries.^1b,2 Among these, helicenes, as prototypical chiral PAHs formed via ortho-fusion of (hetero)aromatic rings, have attracted significant attention.^1c,3 Due to their characteristic emission of left- and right-handed circularly polarized luminescence (CPL), as quantified by dissymmetry factors (g values), helicenes are regarded as promising candidates for chiral luminescent materials. These unique optical properties have rendered helicenes highly attractive for applications in circularly polarized organic light-emitting diodes (CP-OLEDs),^1e,4 organic field-effect transistors (OFETs),⁵ and chiral molecular self-assembly.⁶

To enhance and modulate the chiroptical properties of helicenes, several strategies have been employed: (i) extending the π-conjugation either along the helical axis or laterally;⁷ (ii) introducing electron-donating or electron-withdrawing substituents;⁸ (iii) incorporating multiple helical units within a single molecule to increase structural distortion and intermolecular interactions;⁹ and (iv) doping with main group elements such as B, N, O, P, or S to fine-tune optoelectronic characteristics.^1b,1d,10 Among these approaches, the B atom doping plays a pivotal role in both organic synthesis and optoelectronic materials. Due to its electron-deficient character, the B atom perturbs the electron density distribution, thereby lowering the energy level of the lowest unoccupied molecular orbital (LUMO). Typically, tricoordinate organoboron compounds possess an empty p orbital capable of accepting lone pair electrons from Lewis bases or nucleophiles, thereby forming tetracoordinate organoboron species with tetrahedral geometry.¹¹

Tetracoordinate boron compounds are not only key intermediates in boron chemistry but also represent a promising class of emerging optical materials.¹² These compounds typically comprise bidentate or tridentate ligands coordinated to the boron center, and their photophysical properties can be finely tuned by tailoring the ligand framework and substituents. Notably, boron complexes bearing N^C,¹³ N^N,¹⁴ N^O,¹⁵ and O^O^8a,16 bidentate ligands exhibit high electron affinities and excellent luminescence properties, making them attractive as electron-transport layers in OLEDs or as acceptor units in thermally activated delayed fluorescence (TADF) emitters.¹⁷ Furthermore, boron complexes incorporating tridentate ligands such as C^N^C,^12b,18 O^N^O,¹⁹ and N^N^N^12b,20 have also been developed to further enhance the optical properties and stability. Despite these advances, studies on chiral tetracoordinate boron compounds remain limited, especially those exhibiting helical chirality (Scheme S2, ESI†). Most reported examples are B–N heterohelicenes stabilized through bidentate coordination (e.g., N^C ligands,^13c as illustrated by H1 in Fig. 1), where the B–N bond is positioned at the peripheral region of the helicene framework, thereby experiencing minimal steric hindrance during helix formation. Additionally, the intrinsic instability of dative bonds in tetracoordinate boron complexes compromises their stereochemical stability.²¹ To address this limitation, incorporating B–N units into rigid planar scaffolds via tridentate ligands has emerged as an effective strategy to enhance configurational stability. Although several boron complexes utilizing C^N^C, O^N^O, and N^N^N tridentate coordination modes have been reported, hetero-helicenes with B–N bonds embedded within the inner helical rim, forming an inward-facing configuration, have yet to be disclosed.

Fig. 1 (a) Previously reported azaborole [7]helicene H1 featuring an outer helicene rim with a B–N dative bond and (b) π-extended [8]helicene Hel-BNN, developed in this work, with an inner helicene rim incorporating a N–B–N unit. For clarity, only the (M)-enantiomers are depicted.

Building on our previous work involving the helical tetracoordinate boron compound BN2,^12b derived from an N^N^N tridentate ligand (Fig. 1), we have designed and synthesized a π-extended heterocyclic [8]helicene, Hel-BNN, by introducing the helical conjugated segments at the termini of the molecular backbone. In this compound, the N–B–N unit is embedded within the inner rim of the helical framework. Despite the increased steric hindrance of the precursor, Hel-BNN was efficiently synthesized via a one-pot procedure: the readily accessible pyridyl-based tridentate ligand underwent an N-directed electrophilic borylation reaction in the presence of PhBCl₂ and a base, affording the target compound. Photophysical studies revealed that Hel-BNN exhibits yellow-green fluorescence along with distinct TADF characteristics. The optically pure enantiomers (P- and M-forms) were successfully separated by high-performance liquid chromatography (HPLC), and their chiroptical properties were evaluated using circular dichroism (CD) and CPL spectroscopy. These configurationally stable enantiomers displayed pronounced CPL and circularly polarized electroluminescence (CPEL), with dissymmetry factors (g_lum and g_EL) reaching +2.12 × 10⁻³ and +4.68 × 10⁻⁴, respectively. Notably, electroluminescent devices incorporating Hel-BNN exhibited a peak external quantum efficiency (EQE_max) of up to 22%, highlighting its potential for high-performance circularly polarized TADF applications.

2. Results and discussion

2.1. Molecular design, synthesis, thermal stability, and electrochemical properties

Unlike previously reported B–N helicenes that often rely on dative B ← N bonds within bidentate frameworks, Hel-BNN features a rigid tridentate N^N^N coordination architecture, in which the boron atom is stabilized by one B–N coordination bond and two covalent B–N bonds embedded within a rigid π-conjugated helical backbone. This inward-facing N–B–N motif enforces a locked helical configuration and minimizes structural reorganization, which not only enhances the configurational stability but also induces a stronger chiral perturbation to the electronic transitions. We believe that this unique electronic structure plays a crucial role in amplifying the observed chiroptical response, as compared to the previously reported systems with peripheral B–N arrangements. To construct a more twisted π-conjugated hetero[8]helicene molecule, Hel-BNN, a carbazole derivative (2a), was designed by fusing a benzene ring at the ortho-position of the NH group on the carbazole core. To improve solubility, methyl and tert-butyl groups were introduced at the para-position of the NH group, as illustrated in Scheme 1. Compound 2a was synthesized from 4-methyl-3,4-dihydronaphthalen-1(2H)-one and 4-(tert-butyl)phenylhydrazine hydrochloride via a two-step sequence involving condensation and aromatization reactions, yielding 2a in 65.5% overall yield. Selective bromination of 2a at the fused benzene ring adjacent to the NH group afforded compound 3a in a 78.9% yield. 2D ¹H–¹H COSY NMR analysis confirmed the substitution position of the Br atom (ESI†). A subsequent Suzuki–Miyaura coupling converted 3a into boronate ester 4a with a yield of 70.7%. A second Suzuki coupling between 4a and 2,6-dibromopyridine afforded the precursor ligand 5a in 80.9% yield. Finally, a one–pot N-directed borylation of 5a with dichlorophenylborane (PhBCl₂) in the presence of N,N-dimethyl-p-toluidine (NEti-Pr₂) in o-dichlorobenzene (o-DCB) afforded the four-coordinate N–B–N helicene Hel-BNN in 61% yield. Despite significant steric hindrance, efficient conversion stems from pyridine-boron coordination that generates a B–N complex in situ, and the resulting intermediate, under basic conditions, rapidly and regioselectively forges an intramolecular B–N bond, thereby reducing the entropic penalty of cyclization. Detailed synthetic procedures are provided in the ESI.†

Scheme 1 The illustration of the synthesis of the N^N^N-chelated hetero[8]helicene molecule Hel-BNN.

Hel-BNN exhibits excellent stability toward both moisture and oxygen. It can be purified by silica gel column chromatography and further processed by vacuum sublimation. The structural information was identified by ¹H NMR spectroscopy and high-resolution MALDI-TOF-MS technique. As shown in Fig. 2a, under a nitrogen atmosphere, Hel-BNN exhibits a decomposition temperature (T_d) of about 460 °C at 5% weight loss, significantly higher than that of previously reported N^N^N-chelated boron complexes.^12b This enhanced thermal stability is attributed to the extended π-conjugation within the Hel-BNN framework, which promotes π-electron delocalization and increases molecular rigidity, thereby improving resistance to thermally induced molecular vibrations and bond cleavage.

Fig. 2 (a) Thermogravimetric analysis of Hel-BNN under a nitrogen atmosphere. (b) CV and DPV curves recorded in CH₂Cl₂. (c) Frontier molecular orbital distributions and corresponding energy levels (isovalue = 0.02). (d) Hole–electron distribution derived from natural transition orbital (NTO) analysis.

The cyclic voltammetry measurement of the electrochemistry of Hel-BNN is presented in Fig. 2b, revealing reversible single-electron oxidation and reduction processes. Furthermore, the half-wave potentials derived from differential pulse voltammetry (DPV) are +0.44 V (oxidation) and −2.11 V (reduction) versus Fc/Fc⁺. Based on these values, the HOMO and LUMO energy levels are calculated to be −5.24 eV and −2.61 eV, yielding an energy gap of 2.63 eV. In comparison with the previously reported tetracoordinate molecule BN2, Hel-BNN exhibits higher HOMO and LUMO energy levels, while maintaining a similar energy gap. This suggests that the fused benzene ring in the molecular backbone exerts a minimal effect on the excited energy levels.

2.2. Theoretical calculations

In Hel-BNN, the central B atom exhibits a typical tetrahedral geometry. In addition to forming a B–N coordination bond with the pyridine N atom, it establishes two B–N covalent bonds with the N atoms of the adjacent carbazole units. This unique bonding arrangement plays a crucial role in shaping the electronic structure of the molecule. To elucidate the structural features of Hel-BNN, geometry optimizations in both the ground and excited states were performed using density functional theory (DFT) and time-dependent DFT (TD-DFT) at the B3LYP/6-31G(d) level. As depicted in Fig. S1 (ESI†), Hel-BNN adopts a helically twisted conformation due to significant steric repulsion. In the ground state, the two terminal benzene rings at the carbazole units overlap in a face-to-face manner, forming a dihedral angle of approximately 41.97°. Additionally, one phenyl ring attached to the B center is oriented nearly perpendicular to the tridentate chelating framework, effectively suppressing intermolecular aggregation.

As illustrated in Fig. 2c, the highest occupied molecular orbital (HOMO) is predominantly localized on the peripheral benzo-carbazole segments, whereas the LUMO is mainly distributed over the pyridine moiety, with partial extension onto the benzo-carbazole units. The B atom makes only a minor contribution to both frontier orbitals. This spatial separation between the HOMO and LUMO leads a small singlet–triplet energy gap (ΔE_ST), while still maintaining a favorable radiative transition rate. The calculated HOMO and LUMO energy levels are −4.86 eV and −2.04 eV, respectively, corresponding to a bandgap of 2.82 eV. Moreover, the lowest-energy excitation corresponds to a HOMO → LUMO transition with an oscillator strength (f) of 0.0823 (Fig. S2 and Table S1, ESI†). This excitation is characterized by a hybrid of intramolecular charge transfer (CT) and localized π–π* transitions. Natural transition orbital (NTO) analysis²² of the S₁ state (Fig. 2d) further elucidates the nature of the excited state.

2.3. Photophysical properties

The absorption spectrum of Hel-BNN in toluene solution (1.0 × 10⁻⁵ M) exhibits three primary absorption bands at 331, 383, and 473 nm (Fig. 3a). The low-energy peak at 473 nm corresponds to a molar extinction coefficient of ε = 1.05 × 10⁴ M⁻¹ cm⁻¹. Theoretical calculations suggest that this band primarily arises from a CT transition of HOMO → LUMO. Based on the absorption onset, the optical bandgap (E_g) is estimated to be 2.31 eV, which is slightly lower than that of BN2 (2.36 eV). In toluene, Hel-BNN exhibits orange-yellow photoluminescence (PL), with a peak wavelength (λ_PL) at 572 nm and a photoluminescence quantum yield (Φ_PL) of 60%. Compared to the previously reported BN2 (λ_PL = 567 nm), the λ_PL of Hel-BNN displays a slight red shift, attributed to its extended π-conjugated framework. Notably, the emission spectrum in solution features a full width at half maximum (FWHM) of 95 nm (0.34 eV) and a Stokes shift of 99 nm, indicating strong vibrational coupling and significant structural relaxation between the ground state (S₀) and the first excited state (S₁). The solvent-polarity-dependent absorption and PL spectra further confirm the broad FWHM and the intramolecular CT characteristics of the excited state (Fig. 3b and c).

Fig. 3 (a) Photophysical properties of Hel-BNN in toluene solution or thin film. (b) and (c) Solvent polarity-dependent PL and UV-vis absorption spectra. (d) Fluorescence and phosphorescence spectra were measured at 77 K, with the energy gap estimated from the spectral onset. (e) Temperature-dependent transient decay of Hel-BNN in the doped film. (f) Schematic illustration of the excited-state dynamics for Hel-BNN.

Additionally, the fluorescence and phosphorescence spectra recorded at 77 K (Fig. 3d) were employed to estimate the ΔE_ST, determined to be 0.22 eV. This relatively small gap indicates that reverse intersystem crossing (RISC) from T₁ to S₁ is thermally accessible. Hel-BNN was subsequently doped into a mCPBC host matrix²³ at a ratio of 1.0 wt%, and its PL spectrum at 300 K revealed an emission maximum at 548 nm and a Φ_PL of 50%. The slight blue shift compared to the solution emission is likely due to the lower polarity of the host material. Transient PL decay measurements (Fig. 3e) revealed both prompt fluorescence (τ_PF = 83.6 ns) and delayed fluorescence (τ_DF = 31.9 μs). Furthermore, the temperature-dependent transient PL decay spectra (200–300 K) showed a pronounced enhancement in the delayed component with increasing temperature, corroborating the TADF behavior (Fig. 3f and Table 1). The radiative (k_r) and RISC rate constant (k_RISC) were calculated to be 1.79 × 10⁶ s⁻¹ and 8.61 × 10⁴ s⁻¹, respectively.

Table 1 Photophysical properties of Hel-BNN

λ abs [nm]	λ PL [nm]	FWHM^b [nm eV^−1]	Φ PL [%]	ΔEST^d [eV]	τ F/τDF^e [ns μs^−1]	k r [10^6 s^−1]	k RISC [10^4 s^−1]	HOMO^g [eV]	LUMO^g [eV]
a Recorded in toluene solution. b The spectral bandwidth. c Absolute PL quantum yield measured in solution and doped film. d The energy splitting value. e The prompt and delayed fluorescence lifetime. f Corresponding rate constants. g The HOMO and LUMO energy levels.
473	572	95/0.34	60/50	0.22	83.6/31.9	1.79	8.61	−5.24	−2.61

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2.4. Chiroptical properties

The optimized Hel-BNN structure exhibits a screw-shaped steric configuration, forming a [8]helicene racemic isomer comprising an inner embedded N–B–N unit and the terminal fused benzene rings. Chiral HPLC analysis using a Chiralpak IG-3 column with 2 : 3 (v/v) ethanol/carbon dioxide as the mobile phase identified two configurational isomers: M-Hel-BNN and P-Hel-BNN (Fig. 4a). Enantiomerically pure samples of P-Hel-BNN (first fraction) and M-Hel-BNN (second fraction) were successfully isolated, each with an enantiomeric excess greater than 98.7%. To elucidate the racemization interconversion between M- and P-isomers, DFT calculations were performed at the PBE0/6-311G(d,p) level. The computed racemization pathway, involving an unstable transition state (TS), is illustrated in Fig. 4b. The activation barrier was calculated to be 49.58 kcal mol⁻¹, substantially higher than those reported for previously known hetero-helicenes,^12e indicating that π-conjugation extension within the helical framework markedly increases the racemization barrier.

Fig. 4 (a) Chiral HPLC analysis of racemic Hel-BNN using a Chiralpak IG-3 column (50 × 4.6 mm, 3 μm) with 2 : 3 (v/v) EtOH and CO₂ at a flow rate of 3.0 mL min⁻¹. (b) Computed racemization pathway between M- and P-Hel-BNN, including the relative Gibbs free energies. (c) Simulated CD spectrum of M- and P-Hel-BNN (Gaussian line shape, FWHM = 0.2 eV), along with the experimental CD and CPL spectra in CH₂Cl₂ solution (1.0 × 10⁻⁵ M) at 298 K. (d) Corresponding g_abs and g_PL values for M-Hel-BNN and P-Hel-BNN.

The chiroptical properties of the Hel-BNN enantiomers were subsequently investigated in CH₂Cl₂ solution. Both enantiomers exhibited mirror-image circular dichroism (CD) spectra over the 260–550 nm range, with opposite Cotton effects that closely matched the TD-DFT simulated spectra (Fig. 4c). Notably, P-Hel-BNN displayed a positive Cotton effect in the low-energy region of 350–550 nm. The absorption dissymmetry factor (g_abs), calculated from the ratio of Δε to ε, was plotted as a function of wavelength (Fig. 4d). At the S₀ → S₁ transition (∼469 nm), the enantiomers exhibited large g_abs values of +5.23 × 10⁻³ and −5.11 × 10⁻³. These values are in good agreement with the theoretically calculated |g_abs| value of 6.64 × 10⁻³ (Fig. S3, ESI†). The CPL spectra were also recorded in solution. A pair of mirror-image CPL signals was observed at ∼607 nm, with corresponding g_PL values of +2.12 × 10⁻³ and −2.14 × 10⁻³ (Fig. 4d), comparable to those of previously reported BN-based helicenes.^8c,24

2.5. OLED performance

Given the excellent photophysical and chiroptical properties of Hel-BNN, it was employed as a yellow-emitting material for the fabrication of OLED devices: indium tin oxide (ITO)/HATCN (1,4,5,8,9,11-hexaazatriphenylenehexacarbonitrile, 5 nm)/TAPC (4,4′-(cyclohexane-1,1-diyl)bis(N,N-di-p-tolylaniline), 50 nm)/TCTA (tris(4-(9H-carbazol-9-yl)phenyl)amine, 10 nm)/5 wt% or 7 wt% Hel-BNN: DMIC-TRZ (5-(3-(4,6-diphenyl-1,3,5-triazin-2-yl)phenyl)-7,7-dimethyl-5,7-dihydroindeno[2,1-b]carbazole, 30 nm)/TmPyPB (3,3′-(5′-(3-(pyridin-3-yl)phenyl)-[1,1′:3′,1′′-terphenyl]-3,3′′-diyl)dipyridine, 35 nm)/Liq (1 nm)/Al (100 nm) (Fig. S4, ESI†). The 5 wt% doped device exhibited yellow electroluminescence (EL) with an emission peak at 565 nm, a low turn-on voltage of 2.6 V, a maximum brightness of 3658 cd m⁻², and a peak external quantum efficiency (EQE_max) of 7.19% (Fig. S4, ESI†). This relatively low efficiency is likely due to limited triplet exciton utilization, attributed to the dopant's slow RISC process.

To enhance the triplet exciton utilization, the phosphorescent sensitizer PO-01 (bis(4-phenyl-thieno[3,2-c]pyridinato-C2,N)(acetylacetonato)iridium(III)) was introduced. Consequently, the optimized emission layer comprised a ternary blend of DMIC-TRZ: 20 wt% PO-01: 2 wt% Hel-BNN. The device architecture and chemical structures of the functional molecules are depicted in Fig. 5a and b. Photophysical characterization confirmed efficient energy transfer from PO-01 to Hel-BNN (Fig. 5c). The sensitized device exhibited a low turn-on voltage of 2.5 V and a significantly enhanced luminance, reaching a maximum of 68 300 cd m⁻² (Fig. 5d and Table S2, ESI†). The EL spectra remained stable under varying voltages, emitting intense yellow light with a peak at 567 nm (Fig. 5e). As presented in Fig. 5f and g, the device achieved maximum EQE, current efficiency (CE), and power efficiency (PE) of 21.9%, 59.4 cd A⁻¹, and 74.7 lm W⁻¹, respectively. In addition, the device demonstrated suppressed EQE attenuation at high brightness levels, maintaining EQEs of 17.8% and 15.9% at 100 cd m⁻² and 1000 cd m⁻², respectively. Although this device achieves a relatively lower EQE_max of ∼22%, this value is still noteworthy considering the inherently twisted molecular structure, which often compromises charge transport and Φ_PL. Thus, the performance remains comparable to some of the highest reported values for CP-OLEDs to date (Table S3, ESI†). Furthermore, the circularly polarized electroluminescence (CPEL) of the two enantiomers was investigated (Fig. 5h). The CP-OLEDs exhibited distinct CPEL spectra, with P-Hel-BNN generating a positive EL signal and M-Hel-BNN a negative one. The corresponding g_EL values were +4.68 × 10⁻⁴ and −4.46 × 10⁻⁴ (Fig. S5, ESI†), respectively.

Fig. 5 (a) OLED device structure. (b) The structures of the functional layers in the device. (c) PL of the host material, sensitizer, and Hel-BNN in thin films, along with the energy transfer process. (d) Luminance and current density curves under different voltages. (e) EL spectra at various applied voltages. (f) and (g) CE, PE, and EQE plots at different luminance levels. (h) CP-EL spectra based on P-Hel-BNN and M-Hel-BNN.

3. Conclusions

A helically twisted N^N^N-tridentate chelating tetracoordinate boron [8]helicene, Hel-BNN, was successfully synthesized via a conjugation extension strategy. The complex exhibits excellent thermal stability and reversible redox behavior. Theoretical calculations indicate that Hel-BNN features a hybrid excited state, comprising both CT and localized π–π* transitions, as well as a small ΔE_ST of 0.22 eV, which facilitates the upconversion processes of triplet excitons. In both solution and thin-film states, Hel-BNN demonstrates high Φ_PL exceeding 60%, accompanied by pronounced temperature-dependent delayed fluorescence. Owing to its chiral helical structure, the isolated enantiomers exhibit strong chiroptical activity, including the prominent CD and CPL properties, with |g_abs| and |g_PL| values reaching the order of ±10⁻³. In organic light-emitting diode (OLED) devices, a ternary co-doping strategy incorporating a phosphorescent sensitizer significantly enhances triplet exciton utilization, resulting in an EQE_max of up to 21.9% and effectively suppressing efficiency attenuation at high brightness. This study presents an effective approach for the development of multifunctional chiral TADF materials toward high-efficiency circularly polarized OLEDs.

Author contributions

Junqiao Ding and Guoyun Meng conceived and supervised the study. Yili He, Haoting Yang, and Yuanchun Yue synthesized and characterized the BN emitter, and analyzed the data. Xiangqing Gan, Shuai Xiao and Xian Chen assisted in OLED fabrication and measurement. Shaobiao Zhu, Danrui Wan, Renze He, and Han Si helped with the photophysical characterization and theoretical calculations. Pangkuan Chen provided support for the synthesis and chiral resolution of the BN emitter.

Conflicts of interest

The authors declare no competing interests.

Data availability

The data supporting this article have been included as part of the ESI.†

Acknowledgements

The authors acknowledge the financial support from the National Natural Science Foundation of China (No. 52303253 and 52273198), Yunnan Fundamental Research Project (No. 202501CF070071 and 202301BF070001-008), the Yunling Scholar Project of “Yunnan Revitalization Talent Support Program”, and the Yunnan University Students Innovation and Entrepreneurship Project (S202410673130). We also thank Advanced Analysis and Measurement Center of Yunnan University for assistance with instrumentation. We thank Kaixiang Tu at WuXi AppTec (Wuhan) Co., Ltd for his assistance with chiral analysis and sample preparation.

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Footnotes

† Electronic supplementary information (ESI) available. See DOI: https://doi.org/10.1039/d5tc02210j

‡ These authors contributed equally to this work.

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