In the quest to push the boundaries of photophysical materials, the challenge of achieving efficient red and near-infrared (NIR) emission from boron cation-based luminophores has persisted as a formidable frontier. The inherent instability of boron centers, coupled with their pronounced electrophilic character, restricts the chemical robustness essential for practical applications. Additionally, these compounds typically suffer from severe non-radiative decay pathways, exacerbated by the energy gap law, which becomes increasingly detrimental at longer emission wavelengths. This dual setback has historically limited the exploration and utilization of boron-based emitters in red and NIR spectral regions, despite their immense potential for optoelectronic applications, including bioimaging, telecommunications, and photonic devices.
A pioneering breakthrough has now been achieved by a research team who developed a novel family of carbodicarbene (CDC)-stabilized borabenzo[c]anthanthrenium ions, which exhibit extraordinary stability under ambient air and moisture conditions. These borenium ions showcase solid-state luminescence with emission maxima pushed deep into the red and near-infrared range—reaching up to 730 nanometers—while maintaining competitive quantum yields. This work unfolds a new design paradigm wherein the CDC ligand is not merely a passive spectator but plays an active and dual role: it electronically stabilizes the electrophilic boron center and orchestrates ion-pair assembly via localized charge interactions.
Such a molecular engineering approach is critical for tuning and controlling exciton dynamics and aggregate states, which are vital for achieving efficient long-wavelength emission. The researchers’ meticulous crystallographic, photophysical, and computational investigations reveal that the CDC ligand’s dual function effectively mitigates the strong non-radiative decay channels that have traditionally plagued boron-based emitters. By providing a stable, electron-rich environment, the carbodicarbene stabilizes the positively charged boron, preventing deactivation pathways and enabling the molecule to maintain intense luminescence in the solid state.
The inherent challenge with boron cations relates largely to their high electrophilicity, making them susceptible to nucleophilic attack and prone to degradation in the presence of moisture or oxygen. Overcoming this instability has been a centerpiece of research in boron chemistry, especially when targeting applications requiring durable materials. The integration of the CDC ligand addresses this issue head-on, endowing the borenium ion with air and moisture stability that opens avenues for practical device fabrication and deployment.
From a photophysical standpoint, the newly synthesized boron complexes demonstrate emission properties that are highly desirable for advanced photonic and optoelectronic applications. The red to near-infrared emission window encompasses wavelengths suitable for deep biological tissue penetration and minimal autofluorescence interference, rendering these materials promising for use in biosensing and in vivo imaging. Furthermore, the strong emission combined with stability ensures potential viability in the fabrication of organic light-emitting diodes (OLEDs) and other light-harvesting devices that rely on long-wavelength photons.
A particularly intriguing aspect of this work is the role of ion-pair assembly in modulating the emission properties of the luminescent species. The crystallographic studies reveal that the carbodicarbene ligand helps organize a supramolecular architecture, directing how ions interact in the solid-state environment. This spatial control over ion pairs facilitates excitonic coupling that can either amplify or quench the luminescence depending on the assembly pattern. By intentionally leveraging this charge-directed assembly, the research team shows a robust method for tuning aggregate-state emission, moving beyond isolated molecular properties to understand collective behaviors.
Computational studies further enrich the understanding of the electronic structures involved, highlighting how π-extension through the benzo[c]anthanthrene framework contributes to narrowing the band gap and favoring red-shifted emission. The extended conjugation not only enhances the delocalization of electronic density but also stabilizes the open-shell boron cation, synergizing with the CDC’s electron-donating character. This sophisticated conjugated system exemplifies how careful molecular design balances the competing demands of stability, strong emission, and long-wavelength light output.
Historically, examples of monoboron-doped luminophores effectively emitting in the deep-red to NIR spectrum have been exceedingly rare due to the overlapping complications of reactivity and photophysics. This study represents one of the few instances where these obstacles have been simultaneously surmounted by integrating ligand design, π-conjugation strategies, and supramolecular assembly control. The rarity of such materials underlines the novelty and potential impact of these carbodicarbene borenium ions.
The findings challenge existing paradigms by shifting the focus from merely isolating molecules in solution to embracing controlled solid-state architectures, which are critical for real-world applications. The insight that charge localization and ion pairing can be harnessed as a design principle opens fertile ground for developing a new class of main-group functional materials. This approach aligns with broader trends in materials chemistry, where emergent properties often stem from collective interactions and ordered assembly rather than isolated molecular features.
Moreover, the air- and moisture-stability of these boron complexes cannot be overstated. This quality not only simplifies handling and processing but also significantly expands their applicability across environments where environmental exposure is unavoidable. Such durability is especially vital for next-generation organic semiconductors and sensors that must perform reliably under ambient conditions.
The combination of π-extension and charge-directed assembly mediated by the CDC ligand hints at a modular strategy—one that chemists can adapt and refine to target specific emission wavelengths and material characteristics. This methodological versatility bodes well for the customization of boron-based luminophores tailored to diverse technological requirements, from telecommunications requiring precise wavelength emissions to biomedicine seeking deep-tissue imaging agents.
The present work is also emblematic of the increasing interplay between experimental and computational chemistry, demonstrating how sophisticated modeling can guide molecular design and elucidate complex excited-state phenomena. The synergy between theory and experiment is indispensable for dissecting the multifaceted roles of ligands, electronic structure, and aggregation in defining the photophysical landscape.
While the advances reported here mark a significant leap forward, they also illuminate new questions and future directions. For instance, exploring how substituent variation on the CDC ligand or further π-extension influences emission profiles and stability could expand the photophysical toolkit. Additionally, integrating these boron emitters into device architectures will be an essential next step toward practical application and commercial translation.
In conclusion, the discovery and characterization of this novel class of carbodicarbene-stabilized borenium ions establish a promising pathway for accessing efficient, stable red-to-NIR luminescence from boron-based materials. The strategic union of electronic stabilization, π-conjugation, and ion-pair assembly not only overcomes longstanding challenges but also sets a new benchmark for the design of main-group luminophores. As the photonics and materials science communities seek high-performance, tunable emitters in these spectral regions, this research provides both foundational knowledge and inspiration for future innovation.
This advancement exemplifies the power of chemical ingenuity to unlock the potential of elements traditionally viewed as challenging, expanding the palette of materials available for next-generation photonic technologies. The implications reach across fundamental chemistry and device engineering, promising a vibrant research trajectory and impactful technological breakthroughs in the years to come.
Subject of Research: Development of stable carbodicarbene-boron complexes exhibiting efficient red to near-infrared luminescence through ion-pair assembly and π-extension.
Article Title: Unlocking red-to-near-infrared luminescence via ion-pair assembly in carbodicarbene borenium ions.
Article References:
Deng, CL., Tra, B.Y.E., Zhang, X. et al. Unlocking red-to-near-infrared luminescence via ion-pair assembly in carbodicarbene borenium ions. Nat. Chem. (2025). https://doi.org/10.1038/s41557-025-01941-6
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Tags: bioimaging technologiesboron cation-based luminophorescarbodicarbene borenium ionsCDC ligand stabilizationnon-radiative decay pathwaysOptoelectronic Applicationsphotonic device developmentphotophysical materialsquantum yields in luminescencered near-infrared emissionstable boron emitterstelecommunications advancements
