Emission Quantum Yield Research Articles

Recent Advances of Organic-Inorganic Hybrid Fluorescent Hyperbranched Polymer: Synthesis, Performance Regulation Strategies and Applications.

The organic-inorganic hybrid fluorescent hyperbranched polymer, including hyperbranched polysiloxane and hyperbranched polyborate, have attracted much attention due to their excellent optical properties and wide range of applications. Hyperbranched polysiloxane and polyborates, prepared by introducing Si or B elements into organic polymer chains at the molecular level through rational molecular design and novel synthesis methods, exhibit outstanding photophysical properties as an indispensable branch of organic-inorganic hybrid fluorescent materials. Herein, this review highlights the recent research progress on hyperbranched polysiloxanes and hyperbranched polyborates, including strategies for regulating their emission wavelengths, quantum yields, and fluorescence lifetimes, potential emission mechanisms, and various applications. Finally, some challenges and promising future directions in the field of organic-inorganic hybrid fluorescent polymers are summarized.

Green Synthesis of Luminescent Carbon Dots from Ficus benghalensis Aerial Roots for Bioimaging.

In this work, carbon quantum dots (CQDs) were prepared using a one-step hydrothermal green synthesis method from a low-cost and eco-friendly renewable biomass, specifically the Ficus benghalensis aerial roots (FB-AR). For the past two decades, CQDs have been noted for their tunable emission spectrum, quantum yield, biocompatibility, photostability, and unique optoelectronic properties such as photoluminescence (PL), and fluorescence. The synthesized Ficus benghalensis carbon quantum dots (FB-CQDs) were characterized for their physical, structural, and chemical properties using XRD, Raman, HRTEM, XPS, FTIR, TG-DTG, UV-visible, and photoluminance analysis. XPS analysis confirmed the presence of phytoconstituent functionalities and the composition of components. The FB-CQDs, which exhibit long-range emissions, have potential applications in various biological and therapeutic fields. Their bioimaging capability is tested in Escherichia coli bacteria. However, despite their promising characteristics, the FB-CQDs showed no antibacterial inhibition against Escherichia coli and Staphylococcus aureus, likely due to its carbonization temperature.

Spacer Twisting Strategy to Realize Ultrabright Near-Infrared II Polymer Nanoparticles for Fluorescence Imaging-Guided Tumor Phototheranostics.

Conjugated polymers are becoming popular near-infrared II (NIR-II) phototheranostic agents (PTAs) due to their numerous advantages, such as high photostability, large molar extinction coefficients, and excellent photothermal properties. However, the strong π-π interactions between the chains of the conjugated polymers resulted in their generally low NIR-II emission quantum yields (QY). Therefore, the synthesis of conjugated polymers with high QY is an interesting but challenging task. Herein, we proposed a spacer twisting strategy to realize ultrabright NIR-II polymer nanoparticles for fluorescence imaging-guided tumor phototheranostics. Theoretical calculations indicated that the polymer PY-IT has the largest dihedral angle between the largely π-conjugated skeleton and the spacer, which can effectively inhibit intermolecular π-π stacking, resulting in an improved QY as high as 16.5% in nanoparticles. In addition, PY-IT NPs can effectively perform NIR-II imaging and photothermal treatment of tumors. The work presents some valuable guides for achieving ultrabright NIR-II polymeric PTAs with high QY.

Observation of Three-Photon Cascaded Emission from Triexcitons in Giant CsPbBr3 Quantum Dots at Room Temperature.

Colloidal semiconductor nanocrystals have long been considered a promising source of time-correlated and entangled photons via the cascaded emission of multiexcitonic states. The spectroscopy of such cascaded emission, however, is hindered by efficient nonradiative Auger-Meitner decay, rendering multiexcitonic states nonemissive. Here we present room-temperature heralded spectroscopy of three-photon cascades from triexcitons in giant CsPbBr3 nanocrystals. We show that this system exhibits second- and third-order correlation function values, g(2)(0) and g(3)(0,0), close to unity, identifying very weak binding of both biexcitons and triexcitons. Combining fluorescence lifetime analysis, photon statistics, and spectroscopy, we can readily identify emission from higher multiexcitonic states. We use this to verify emission from a single emitter despite high emission quantum yields of multiply excited states and comparable emission lifetimes of singly and multiply excited states. Finally, we present potential pathways toward control of the photon number statistics of multiexcitonic emission cascades.

Cationic or Neutral: Dependence of Photophysical Properties of Bis-Alkynylphosphonium Pt(II) Complexes on Ancillary Ligand.

A series of D-π-A alkynylphosphonium salts with different linker between donor and acceptor groups was used to synthesize two series of trans-bis-alkynylphosphonium Pt(II) complexes with different ancillary ligands (triphenylphosphine, P series, and cyanide, CN series). The nature of the ancillary ligand manages the overall charge and emission properties of the complexes obtained. In addition, the variation of the linker in alkynylphosphonium ligands allows fine-tuning the luminescence wavelength. Dicationic series P is unstable in solution under UV excitation, whereas in the solid state, these complexes are the first example of phosphorescent trans-phosphine-bis-alkynyl Pt(II) compounds. Neutral series CN demonstrates bright emission in solution, including dual emission for 2CN complex with biphenyl linker in alkynylphosphonium ligand. However, in the solid state for the CN series drastic decrease in the emission quantum yield compared to the P series was observed. DFT calculations reveal the complicated emission nature for the both P and CN series with various contributions of 3ILCT, 3LLCT and 3MLCT states. However, in the naphthyl-containing derivatives 3P and 3CN, the dominating 3LC character with some admixture of CT states is postulated.

Controllable 1,4-Palladium Aryl to Aryl Migration in Fused Systems─Application to the Synthesis of Azaborole Multihelicenes.

Herein, we report the first 1,4-Pd aryl to aryl migration/Miyaura borylation tandem reaction in fused systems. The Pd shift occurred in the bay region of the dibenzo[g,p]chrysene building blocks, giving rise to a thermodynamically controlled mixture of 1,8- and 1,9-borylated compounds that allowed the preparation of regioisomeric azaborole multihelicenes from the same starting material. The outcome of this synthesis can be controlled by the choice of reaction conditions, allowing the migration process to be turned off in the absence of an acetate additive and the target multiheterohelicenes to be prepared in a regioselective manner. The target compounds show bright green fluorescence in dichloromethane with emission quantum yields (Φ) of up to 0.29, |glum| values up to 2.7 × 10-3, and green or green-yellow emission in the solid state, reaching Φ of 0.22. Single crystal X-ray diffraction analyses gave insight into their molecular structures and the packing arrangement. Evaluation of aromaticity in these multihelicenes revealed a nonaromatic character of the 2H-1,2-azaborole constituent rings.

Versatile Nanolights From Silicon, Carbon and Oxygen Hybrid System for Optical Applications

AbstractSilicon, carbon and oxygen hybrid nanomaterials (i.e., SiCOHNs) have recently drawn extensive attention as versatile photoluminescence (PL) nanosystems. The collective advantages of silicon‐ and carbon‐based nanostructures have resulted in SiCOHNs with tunable and photostable PL properties, abundant possibilities for surface modification, and low biotoxicity. Although SiCOHNs have shown great potential in diverse applications, such as bioimaging, biosensing, drug delivery and information encryption, discovering novel SiCOHNs with explicit nanostructures and elucidating the fundamental mechanisms of their PL properties for bioapplications are highly desirable. In this review, on the preparation of SiCOHNs on the basis of the synthesis conditions and precursors are first focused. Next, the manipulation of the emission wavelength, quantum yield and RTP of SiCOHNs is discussed. On the basis of previous reports and the recent experimental/theoretical results, the primary structure of SiCOHNs is clarified and deduced their possible PL mechanism. SiCOHNs possess bacterial uptake efficiency and/or anticancer capacity, promoting various biomedical applications and proof‐of‐concept applications in anti‐counterfeiting. Finally, current challenges and future trends are summarized as a roadmap for the development of SiCOHNs‐based optical applications.

Organic doped red room-temperature afterglow materials based on 2,3,5-triarylfuro[3,2-b]pyridines through Förster-resonance energy transfer

A series of novel 2,3,5-triarylfuro[3,2-b]pyridines are designed and acquired to be used as the guest molecules in organic doped room-temperature phosphorescence (RTP) system. Phenyl(pyridin-2-yl)methanone which can provide the rigid and tight microenvironment is chosen as the host molecule, which enables the two-component doped materials to emit RTP emissions of 0.5–8 s with 41–565 ms phosphorescence lifetimes and 2.9–19.4 % phosphorescence quantum efficiencies through constricting the non-radiative decay of triplet excitons. Furthermore, using commercial dyes Erythrosin B sodium salt and Eosin Y sodium salt as the third component and energy acceptor, the three-component materials emit bright red afterglows of 2 s with delayed lifetimes of 252–286 ms and emission quantum yields of 5.1–5.6 %, which are demonstrated to come from the triplet-to-singlet Förster-resonance energy transfer (FRET) from phosphorescence emission of 2,3,5-triarylfuro[3,2-b]pyridine derivative to fluorescence emission of commercial dye. This work not only provides valuable reference for the development of furo[3,2-b]pyridine-based afterglow materials, but also proves that the strategy of the FRET process provides new possibilities for molecules that can only emit fluorescence to participate in constructing afterglow materials.

Efficient Blue Emission in Organic–Inorganic Metal Halide (TEA)2InCl5 Triggered by Bi3+‐Doping

AbstractLead‐free 0D In‐based organic–inorganic metal halides (OIMHs) have attracted tremendous attention because of their nontoxicity, environmental stability, and excellent photoluminescence properties. However, it remains controversial and unclear whether the luminous division exists in ns2 doping In‐based materials, as the majority of In‐based materials are considered non‐luminous. Herein, a series of Bi3+‐doped (TEA)2InCl5 (TEA = tetraethylammonium) crystals are synthesized and it is determined that the blue emission stemmed from Bi ions. Remarkably, the photoluminescence quantum yield (PLQY) of the blue emission at 469 nm reached 69.69% under 371 nm excitation, exceeding those of previously reported Bi3+‐doped OIMHs. In addition, pristine and Bi3+‐doped compounds exhibited excellent structure and optical stability under humid conditions. This study provides new insights into the photoluminescence properties of In‐based OIMHs, especially regarding the high‐efficiency emission of Bi3+‐doped materials.

Raising Near-Infrared Photoluminescence Quantum Yield of Au42 Quantum Rod to 50% in Solutions and 75% in Films.

Highly emissive gold nanoclusters (NCs) in the near-infrared (NIR) region are of wide interest, but challenges arise from the excessive nonradiative dissipation. Here, we demonstrate an effective suppression of the motions of surface motifs on the Au42(PET)32 rod (PET = 2-phenylethanethiolate) by noncoordinative interactions with amide molecules and accordingly raise the NIR emission (875/1045 nm peaks) quantum yield (QY) from 18% to 50% in deaerated solution at room temperature, which is rare in Au NCs. Cryogenic photoluminescence measurements indicate that amide molecules effectively suppress the vibrations associated with the Au-S staple motifs on Au42 and also enhance the radiative relaxation, both of which lead to stronger emission. When Au42 NCs are embedded in a polystyrene film containing amide molecules, the PLQY is further boosted to 75%. This research not only produces a highly emissive material but also provides crucial insights for the rational design of NIR emitters and advances the potential of atomically precise Au NCs for diverse applications.

POE-Mediated Tunable Quantum Yield of Carbon Dots-Derived From Agapanthus Africanus (L.) Hoffmann Leaves.

The green synthesis of carbon dots (CDs) from natural sources is a challenging goal. Herein CDs are produced from Agapanthus africanus (L.) Hoffmann leaves by carbonization at 200/300 °C for 2/3h. Samples are named CZ-X-Y, where Z, X, and Y represent carbonization, temperature, and time, respectively. CZ-200-3, CZ-300-2, and CZ-300-3 CDs have average sizes of 3.7 ± 0.7, 5.3 ± 1.2, and 5.1 ± 1.6nm, respectively. Their surface, devoid of chlorophyll, contains ─OH, ─C═O, and ─C(═O)OH groups and sylvite. Isolated CZ-300-3 emits at 400nm (excited at 260nm) and exhibits an emission quantum yield (QY) value of 2 ± 1%. Embedding in the d-U(600)/d-(900) di-ureasil matrices resulted in transparent films with emission intensity maxima at 420/450nm (360nm), and QY values of 7 ± 1/16 ± 2% (400nm). The enhancement of the QY value of the bare CDs agrees withan efficient passivation provided by the hybrid host. The hydrophilic CZ-300-3 CDs also exerted a marked surface modifying role, changing the surface roughness and the wettability of the hybrid films.

Inflated electronic and optical assessment of gC3N4/ZnO nanocomposite as a potential emissive layer material for OLED application

Organo-inorganic nanocomposite materials have been proven to be novel hybrid materials with inflated electronic and optical performance that can be tailored with the judicious selection of the building units or their combinations. Here, hydrothermal, thermal polycondensation, and ultrasonication techniques were used to synthesize pure ZnO, gC3N4, and gC3N4/ZnO with varying weights % such as 10%, 15%, 20%, and 25% of ZnO inorganic filler elements in gC3N4 matrix. The crystalline phase (hexagonal wurtzite) and crystallite size (10.0 nm, 17.6 nm, and 15.90 nm) of the synthesized materials were examined by X-ray diffractometer. The FESEM and HRTEM characterizations revealed the sheet-like gC3N4 and spherical-type ZnO nanoparticle-like microstructures of the samples. The present functional groups, corresponding vibrational frequency, chemical states, and binding energy were investigated using FTIR and XPS spectroscopic methods. Optical parameters such as optical band gap energy (Eg = 3.24 eV), Urbach energy (Eu = 0.41 eV), refractive index (n= 1.99), emission quantum yield (∼ 69.03%), and color purity of the nanocomposites were examined using UV visible and photoluminescence spectroscopic techniques. IV and Hall measurements techniques were used to determine the semiconducting parameters of the optimized sample, such as conductivity (∼62.90×10−5 S/cm), carrier mobility (∼ 44.1 cm2/Volt. Sce), carrier concentrations (∼1.825×1014 cm−3), and sheet resistance (∼1.062×103 Ω/cm2). Due to their excellent optical and electrical behavior, the nanocomposite materials were found to be fairly suitable as a potential emissive layer material for OLED applications.

Golden Guardians: Advanced pH Sensors with Built‐in Antimicrobial Defense

AbstractGold nanoclusters (Au NCs) capped with a small biomolecule, namely (+)‐norephedrine, (Au@Nore) display exceptional performance as fluorescent pH sensors. They display high emission quantum yield (ΦPL of ≈33% in strongly basic media); absence of nanocluster (NC) aggregation and/or induced rigidification of the organic shell; a linear dependency of their emission on the pH in the 8.2–9.5 range; and reversible pH sensing. In addition, excitation at 310 nm, where both the NC and the ligand absorb, enables ratiometric sensing. Studies on the fungus Candida albicans and bacterium Bacillus subtilis demonstrate that while Au@Nore do not cause any impact on the growth of the fungus, it inhibited the growth of the Bacillus, showing the lowest cell viability of 18% at the highest pH values via a mechanism of action involving the disruption of the bacterial wall.

A non-symmetric room-temperature tristriazolotriazine liquid crystal

Tristriazolotriazine (TTT) has emerged as an easily accessible electron-deficient heterocyclic core for discotic liquid crystals (LCs). Materials that are liquid-crystalline at room temperature, i.e., do not crystallize in ambient conditions, are of particular interest when the LC state is prone to offer advantages in optoelectronic devices, e.g., for anisotropic charge or exciton transport, or anisotropic light emission. However, there has been no report of non-symmetric TTT LCs, i.e., with unequal arms. Here, we report two non-symmetric compounds derived from the TTT core. Their non-symmetry, combined with a high number of peripheral alkyl chains, is found to promote Colh mesomorphism over a broad temperature range including room temperature. The non-symmetry also induces an increase in the emission quantum yield, compared to symmetric analogs.

Deciphering TADF Mechanisms in Metal-Free Organic Emitters BrA-HBI: Utilizing Optimally Tuned Range-Separated Functionals for Insight

Abstract Metal-free organic emitters, characterized by their thermally activated delayed fluorescence (TADF) properties, offer considerable promise for the creation of highly efficient organic light-emitting diodes (OLEDs). Recently, Shao et al. presented a novel excited state intramolecular proton transfer (ESIPT) system BrA-HBI, demonstrating an emission quantum yield of up to 50% [Adv. Funct. Mater. 32, 2201256 (2022)]. However, many open issues cannot be answered solely by experimental means only and require detailed theoretical investigations. For instance, what causes the activation of TADF from the Keto* tautomer and leads to fluorescence quenching in the Enol* form? Herein, we provide a theoretical investigation on the TADF mechanism of the BrA-HBI molecule by optimally tuned range-separated functionals. Our findings reveal that ESIPT occurs in the BrA-HBI molecule. Moreover, we have disclosed the reason for the fluorescence quenching of the Enol* form and determined that the T 2 state plays a dominant role in the TADF phenomenon. In addition, double hybrid density functionals method was utilized to verify the reliability of optimally tuned range separation functionals on the calculation of the TADF mechanism in BrA-HBI. These findings not only provide a theoretical reference for development of highly efficient organic light-emitting diodes, but also demonstrate the effectiveness of the optimally tuned range-separated functionals in predicting the luminescence properties of TADF molecules.

Biocompatible bright orange emissive carbon dots: Multifunctional nanoprobes for highly specific sensing toxic Cr(VI) ions and mitochondrial targeting cancer cell imaging

Although several luminescent-based nanostructured materials are used as cellular imaging probes, creating a biocompatible subcellular imaging probe can be challenging. Instantaneously, it is crucial and urgently needed for certain fluorescent nanoprobes to identify possibly harmful heavy metal ions. We present a straightforward one-pot preparation of bright orange emissive (quantum yield approximately 16 %) Nitrogen/Sulfur co-doped carbon dots (N/S CDs) from citric acid and methylene blue as raw materials that will serve as a specific Cr(VI) ions sensor and an effective mitochondrial labeling in cancer cells. They had several benefits including low ecological impact, facile synthesis, good water solubility, photostability, and high stability. We found that N/S CDs photoluminescence (PL) could be reduced when Cr(VI) ions were present near them, and the PL reduction occurred highly sensitively to the presence of Cr(VI) compared to other metal ions including Cr(III) ions. This specific reduction of PL was due to the non-fluorescent complex formation through the inner filter effect (IFE). The established fluorescence-based sensing technique could serve for Cr(VI) ion quantification with exceptional sensing efficiency in the wide linear range of 7 to 70 μM (R2 = 0.9873), with the limit of detection of 53.5 nM. It was also revealed that the current fluorescent probe could be encouragingly utilized to quantify the concentration of Cr(VI) ions in various water specimens such as tap water. In addition, they were shown to function as a mitochondria-targeting nanoprobe in human cancer cells (ME 180 cells and Hela cells) for cell imaging. Concludingly, it was envisioned that these fluorescent nanoprobes could find a use in real-time monitoring of Cr(VI) ions in water-based ecosystems with ultrahigh sensitivity and cell image tracking via mitochondria labeling as biocompatible nanoprobes.

Unusually Large Ligand Field Splitting in Anionic Europium(III) Complexes Induced by a Small Imidazolic Counterion.

Luminescent trivalent lanthanide (Ln3+) complexes are compounds of technological interest due to their unique photophysical properties, particularly anionic tetrakis complexes, given their higher stability and emission quantum yields. However, structural studies on the cation-anion interaction in these complexes and the relation of such to luminescence are still lacking. Herein, the cation-anion interactions in two luminescent anionic tetrakis(2-thenoyltrifluoroacetonato)europate(III) complexes with alkylimidazolium cations, specifically 1-ethyl-3-methylimidazolium and 1-butyl-3-methylimidazolium are investigated. The Eu3+ complexes were synthesized and characterized by elemental analysis, mass spectrometry, and single-crystal X-ray crystallography, and their luminescence spectra were recorded at 77 K. Quantum chemical calculations were also performed. X-ray crystallography revealed hydrogen bonds between the enolate ligands and imidazolium ring hydrogens. The 1-butyl-3-methylimidazolium complex had two crystallographic Eu3+ sites, also confirmed by luminescence spectroscopy. The 1-ethyl-3-methylimidazolium complex exhibited an unusual 300 cm-1 splitting in the 5D0 → 7F1 transition, as reproduced by ligand field calculations, suggesting a stronger hydrogen bonding due to the smaller substituent. We hypothesize that this strong bonding likely causes angular distortions, resulting in high ligand field splittings.

Effect of Mn2+ doping and DDAB-assisted postpassivation on the structural and optical properties of CsPb(Cl/Br)3 halide perovskite nanocrystals

Cesium lead halide perovskite (CsPbX3; X = Cl, Br, I) nanocrystals showing intense band-edge emission and high photoluminescence quantum yield are known to be a potential candidate for application in optoelectronic devices. However, controlling toxicity due to the presence of Pb2+ in lead-based halide perovskites is a major challenge for the environment that needs to be tackled cautiously. In this work, we have partially replaced Pb2+ with Mn2+ ions in the CsPb(Cl/Br)3 nanocrystals and investigated their impact on the structural and optical properties. The Rietveld refinement shows that CsPbCl2Br nanocrystals possess a cubic crystal structure with Pm 3̅ m space group, the Mn2+ doping results in the contraction of the unit cell. The CsPb(Cl/Br)3: Mn nanocrystals show a substantial change in the optical properties with an additional emission band at ∼588 nm through a d-d transition, changing the emission color from blue to pink. Here, a didodecyldimethylammonium bromide (DDAB) ligand that triggers both anion and ligand exchange in the CsPb(Cl/Br)3: Mn nanocrystals have been used to regulate the exchange reaction and tune the emission color of halide perovskites by changing the peak position and the PL intensities of band-edge and Mn2+ defect states. We have also shown that oleic acid helps in the desorption of oleylamine capping from the CsPb(Cl/Br)3: Mn nanocrystal surfaces and DDAB, resulting in the substitution of Cl− with Br− as well as provides capping with shorter branched length ligand which led to increase in the overall PL intensity by many folds.

Excited-State Dynamics of a Bright Fluorescent Dye with Precise Control of Emission Color Using Acid-Base Equilibrium, Intramolecular Charge Transfer, and Host-Guest Chemistry.

A fluorescent dye, a dithiophene-conjugated benzothiazole derivative (DTBz), was prepared to have high fluorescence emission quantum yields (ΦF) across various organic solvents. Its emission color modulation, from bright blue to deep red, was achieved through intramolecular charge transfer (ICT), acid-base equilibrium, and host-guest chemistry. Although it exhibits a weak solvatochromic effect, DTBz exhibited a bright fluorescence emission around 480 nm upon excitation at 390 nm in most solvents. In polar solvents, such as MeOH (methanol), EtOH (ethanol), DMF (N,N-dimethylforamide), and DMSO (dimethyl sulfoxide), an additional ICT emission band emerged around 640 nm, notably intense in DMSO, resulting in a bright greenish-white emission (ΦF = 0.67). The addition of 1,8-diazabicyclo[5,4.0]undec-7-ene (DBU) altered emission characteristics, reducing emission from the local excited (LE) state and enhancing ICT state emission. The degree of emission spectral change saturation with DBU addition varied with the solvent nature. Polar solvents with high dielectric constants, like DMSO and DMF, saw a complete disappearance of LE state emission with 5 equiv of DBU, resulting in a deep red emission (ΦFs of 0.53 and 0.48, respectively). Femtosecond transient absorption spectroscopy and time-resolved photoluminescence measurements elucidated the excited-state dynamics, revealing a long-lived excited state (τ-H = 10.3 ns) at a lower energy emission (640 nm), identified as DTBz-*, supported by transient absorption spectra analysis. Further analysis, including time-resolved fluorescence decay measurements and time-dependent density-functional theory (TD-DFT) calculations, underscored the role of deprotonation of DTBz's hydroxyl group in promoting the ICT process. The CIE coordination plot demonstrated wide linear emission color changes upon successive DBU additions in all solvents, while emission color precision was achieved through host-guest chemistry. Emission changes induced by DBU were reverted to the original state upon beta-cyclodextrin (β-CD) addition, with the 1H NMR study revealing the competition between acid-base equilibrium and host-guest complex formation as the cause of emission color change.

Exploring the Potential of Al(III) Photosensitizers for Energy Transfer Reactions.

Three homoleptic Al(III) complexes (Al1-Al3) with different degrees of methylation at the 2-pyridylpyrrolide ligand were systematically tested for their function as photosensitizers (PS) in two types of energy transfer reactions. First, in the generation of reactive singlet oxygen (1O2), and second, in the isomerization of (E)- to (Z)-stilbene. 1O2 was directly evidenced by its characteristic NIR emission at around 1276 nm and indirectly by the reaction with an organic substrate [e.g. 2,5-diphenylfuran (DPF)] using in situ UV/vis spectroscopy. In a previous study, the presence of additional methyl groups was found to be beneficial for the photocatalytic reduction of CO2 to CO, but here Al1 without any methyl groups exhibits superior performance. To rationalize this behavior, a combination of photophysical experiments (absorption, emission and excited state lifetimes) together with photostability measurements and scalar-relativistic time-dependent density functional theory calculations was applied. As a result, Al1 exhibited the highest emission quantum yield (64%), the longest emission lifetime (8.7 ns) and the best photostability under the reaction conditions required for the energy transfer reactions (e.g. in aerated chloroform). Moreover, Al1 provided the highest rate constant (0.043 min-1) for the photocatalytic oxygenation of DPF, outperforming even noble metal-based competitors such as [Ru(bpy)3]2+. Finally, its superior photostability enabled a long-term test (7 h), in which Al1 was successfully recycled seven times, underlining the high potential of this new class of earth-abundant PSs.