Magnetic circularly polarized luminescence from spin-flip transitions in a molecular ruby

Magnetic circularly polarized luminescence (MCPL), i.e. the possibility of generating circularly polarized luminescence in the presence of a magnetic field in achiral or racemic compounds, is a technique of rising interest. Here we show that the far-red spin-flip (SF) transitions of a molecular Cr(iii) complex give intense MCD (magnetic circular dichroism) and in particular MCPL (g MCPL up to 6.3 × 10-3 T-1) even at magnetic fields as low as 0.4 T. Cr(iii) doublet states and SF emission are nowadays the object of many investigations, as they may open the way to several applications. Due to their nature, such transitions can be conveniently addressed by MCPL, which strongly depends on the zero field splitting and Zeeman splitting of the involved states. Despite the complexity of the nature of such states and the related photophysics, the obtained MCPL data can be rationalized consistently with the information recovered with more established techniques, such as HFEPR (high-frequency and -field electron paramagnetic resonance). We anticipate that emissive molecular Cr(iii) species may be useful in magneto-optical devices, such as magnetic CP-OLEDs.

Recent trends for chemoselectivity modulation in one-pot organic transformations

In organic reactions, chemoselectivity refers to the selective reactivity of one functional group in the presence of another. This can be more successful if the reagent and reaction parameters are appropriately chosen. One-pot reactions have been shown to be an effective structural variety technique for the development of novel heterocyclic or carbocyclic compounds. This review article focuses on recent efforts by researchers from around the world to synthesise novel organic molecules utilising these methodologies (2013-2024), as well as their mechanism insights. The substrate, catalyst, solvent, and temperature conditions all have a significant impact on chemoselectivity in the organic reactions described here. The manipulation of chemoselectivity in organic processes creates new potential for the production of novel heterocycles and carbocycles.

π-Extended ligands with dual-binding behavior: hindered rotation unlocks unexpected reactivity in cyclometalated Pt complexes

Cyclometalated platinum complexes play a crucial role in catalysis, bioimaging, and optoelectronics. Phenylpyridines are widespread cyclometalating ligands that generate stable and highly emissive Pt complexes. While it is common practice to modify these ligands to fine-tune their photophysical properties, the incorporation of polycyclic aromatic hydrocarbons into the ligand's structure has been largely overlooked. This report describes the cyclometalation of naphthalenyl- and anthracenylpyridine ligands, which has resulted in ten new luminescent PtII and PtIV complexes. These species are enabled by a dual-binding behavior discovered in our polyaromatic-containing ligands. The introduction of naphthalenyl and anthracenyl groups unlocks dual binding modes, with the Pt center bonding to either of two distant carbon atoms within the ligand. These complexes exhibit both symmetric structures with two 5-membered metallacycles and asymmetric structures with 5- and 6-membered metallacycles. This work presents a strategy for the regioselective synthesis of Pt complexes with bespoke structures and photophysical properties. Our findings offer new opportunities in platinum chemistry and beyond, with potential implications for materials and technologies.

Shining New Light on Biological Systems: Luminescent Transition Metal Complexes for Bioimaging and Biosensing Applications

Luminescence imaging is a powerful and versatile technique for investigating cell physiology and pathology in living systems, making significant contributions to life science research and clinical diagnosis. In recent years, luminescent transition metal complexes have gained significant attention for diagnostic and therapeutic applications due to their unique photophysical and photochemical properties. In this Review, we provide a comprehensive overview of the recent development of luminescent transition metal complexes for bioimaging and biosensing applications, with a focus on transition metal centers with a d6, d8, and d10 electronic configuration. We elucidate the structure-property relationships of luminescent transition metal complexes, exploring how their structural characteristics can be manipulated to control their biological behavior such as cellular uptake, localization, biocompatibility, pharmacokinetics, and biodistribution. Furthermore, we introduce the various design strategies that leverage the interesting photophysical properties of luminescent transition metal complexes for a wide variety of biological applications, including autofluorescence-free imaging, multimodal imaging, organelle imaging, biological sensing, microenvironment monitoring, bioorthogonal labeling, bacterial imaging, and cell viability assessment. Finally, we provide insights into the challenges and perspectives of luminescent transition metal complexes for bioimaging and biosensing applications, as well as their use in disease diagnosis and treatment evaluation.

Synthesis, Photoluminescence, and Electroluminescence of Phosphorescent Dipyrido[3,2-a;2'3'-c]phenazine-Platinum(II) Complexes Bearing Hole-Transporting Acetylide Ligands

In this study, novel phosphorescent dipyrido[3,2-a;2'3'-c]phenazine (dppz)-platinum(II)-phenylacetylide complexes were developed to fabricate non-doped organic light-emitting diodes (OLED) by solution-processing. To facilitate the charge carrier injection into the emitting layer (EML), 3,6-di-tert-butylcarbazole-functinalized phenylacetylides were employed. As for the dppz ligand, 9,9-dihexylfluoren-2-yl and 4-hexylthiophen-2-yl side-arms were introduced to the 2,7-positions, which led to reddish orange and red photoluminescence (PL), respectively, in solution and film states (PL wavelength: ca. 600 and ca. 625 nm, respectively). The carbazole-appended phenylacetylide ligands hardly affected the emission color, although unsubstituted phenylacetylides gave rise to aggregate- or excimer-based near-infrared PL with a low quantum yield. Two types of non-doped OLEDs were fabricated: single-layer and multilayer devices. In both devices, the organic layers were fabricated by spin-coating, and the EML consisted of a neat film of the corresponding platinum(II) complex. Therein, electroluminescence spectra corresponding to those of PL were observed. The single-layer devices exhibited low device efficiencies due to a deteriorated charge carrier balance. The multilayer devices possessed hole- and electron-transporting layers on the anode and cathode sides of the EML, respectively. Owing to an improved charge carrier balance, the multilayer devices exhibited higher device performance, affording considerably improved values of luminance and external quantum efficiency.

Terpyridine-Decorated Polymer Nanosphere Latex: Template Nanocarriers for the Synthesis of Cu-CeO2 Hollow Spheres

Water-soluble polymers with the ability to complex metal ions through complexing ligands have attracted significant interest in diverse domains, such as optical or catalyst applications. In this paper, we successfully synthesized, through a one-pot process combining polymerization-induced self-assembly and reversible addition-fragmentation chain transfer polymerization, aqueous dispersions of terpyridine-decorated poly[poly(ethylene glycol)methyl ether methacrylate]-b-poly(methyl methacrylate) (tpy-PPEGMA-b-PMMA) amphiphilic block copolymers. The in-situ formation of well-defined amphiphilic block copolymers and their self-assembly led to nanosphere latex with the hydrodynamic diameters increasing from 17 to 52 nm and the length of the copolymers increasing from 21,000 to 51,000 g·mol-1. These aqueous dispersed tpy-PPEGMA-b-PMMA nanospheres effectively complex metal ions, such as Cu2+, in a stoichiometric ratio of 2:1. Subsequently, these metal-complexed nanospheres were employed as soft template nanocarriers to control, on the nanometer scale, the dispersion of metal on a nanostructured support. This is exemplified by the synthesis of copper supported on cerium oxide hollow spheres (Cu-CeO2) using Cu2+-tpy-PPEGMA-b-PMMA as template nanocarriers and CeO2 nanoparticles. This novel assembly engineering strategy for the preparation of atomically dispersed metal on a nanostructured support was highlighted through the utilization of Cu-CeO2 hollow spheres as an electrocatalyst for the nitrate reduction reaction (NO3RR) to NH3. These encouraging outcomes emphasize the potential of metal-metal oxide-nanostructured materials to treat contaminated water sources with nitrate while allowing the green production of ammonia.

Luminescent Tetranuclear Copper(I) and Gold(I) Heterobimetallic Complexes: A Phosphine Acetylide Amidinate Orthogonal Ligand Framework for Selective Complexation

The synthesis of phosphine acetylide amidinate stabilized copper(I) and gold(I) heterobimetallic complexes was achieved by reacting ligand [{Ph2PC≡CC(NDipp)2}Li(thf)3] (Dipp=2,6-N,N'-diisopropylphenyl) with CuCl and Au(tht))Cl, yielding the eight membered ring [{Ph2PC≡CC(NDipp)2}2Cu2] and the twelve membered ring [{Ph2PC≡CC(NDipp)2}2Au2]. {Ph2PC≡CC(NDipp)2}2Cu2] features a Cu2 unit, which is bridged by two amidinate ligands, served as a metalloligand to synthesize the heterobimetallic CuI/AuI complexes [{(AuX)Ph2PC≡CC(NDipp)2}2Cu2] (X=Cl, C6F5). In these reactions, the central ring structure is retained. In contrast, when the twelve membered ring [{Ph2PC≡CC(NDipp)2}2Au2] was reacted with CuX (X=Cl, Br, I and Mes), the reaction led to the rearrangement of the central ring structure to give [{(AuX)Ph2PC≡CC(NDipp)2}2Cu2] (X=Cl, Br, I and Mes), which feature the same the eight membered Cu2 ring as above. These compounds were also synthesized by a one-pot reaction. The luminescent heterobimetallic complexes were further investigated for their photophysical properties.

A family of Cd(II) coordination polymers constructed from 6-aminopicolinate and bipyridyl co-linkers: study of their growth in paper and photoluminescence sensing of Fe3+ and Zn2+ ions

In this work, we report on five novel coordination polymers (CPs) based on the linkage of the [Cd(6apic)2] building block [where 6apic = 6-aminopicolinate] by different bipyridine-type organic spacers, forming different coordination compounds with the following formulae: [Cd(μ-6apic)2]n (1), {[Cd(6apic)2(μ-bipy)]·H2O}n (2), {[Cd(6apic)2(μ-bpe)]·2H2O}n (3), [Cd(6apic)(μ-6apic)(μ-bpa)0.5]n (4) and {[Cd2(6apic)4(μ-tmbp)]·7H2O}n (5) [where bipy = 4,4'-bipyridine, bpe = 1,2-di(4-pyridyl)ethylene, bpa = 1,2-di(4-pyridyl)ethane (bpa) and tmbp = 1,3-di(4-pyridyl)propane]. Most of the synthesized compounds form infinite metal-organic rods through the linkage of the building block by the bipyridine-type linker, except in the case of compound 4 whose assembly forms a densely packed 3D architecture. All compounds were fully characterized and their photoluminescence properties were studied experimentally and computationally through density functional theory (DFT) calculations. All compounds display, upon UV excitation, a similar blue emission of variable intensity depending on the linker employed for the connection of the building units, among which compound 2 deserves to be highlighted for its room temperature phosphorescence (RTP) with an emission lifetime of 32 ms that extends to 79 ms at low temperature. These good photoluminescence properties, in addition to its stability in water over a wide pH range (between 2 and 10), motivated us to study compound 2 as a sensor for the detection of metal ions in water, and it showed high sensitivity to Fe3+ through a fluorescence turn-off mechanism and an unspecific turn-on response to Zn2+. Furthermore, the compound is processed as a paper-based analytical device (PAD) in which the phosphorescence emission is preserved, improving the sensing capacity toward Fe3+ ions.

Highly Stable MOF-Type Lead Halide Luminescent Ferroelectrics

Lead halide molecular ferroelectrics represent an important class of luminescent ferroelectrics, distinguished by their high chemical and structural tunability, excellent processability and distinctive luminescent characteristics. However, their inherent instability, prone to decomposition upon exposure to moisture and light, hinders their broader ferroelectric applications. Herein, for the first time, we present a series of isoreticular metal-organic framework (MOF)-type lead halide luminescent ferroelectrics, demonstrating exceptional robustness under ambient conditions for at least 15 months and even when subjected to aqueous boiling conditions. Unlike conventional metal-oxo secondary building units (SBUs) in MOFs adopting highly centrosymmetric structure with limited structural distortion, our lead halide-based MOFs occupy structurally deformable [Pb2X]+ (X=Cl-/Br-/I-) SBUs that facilitate a c-axis-biased displacement of Pb2+ centers and substantially contribute to thermoinducible structural transformation. Importantly, this class of MOF-type lead halide ferroelectrics undergo ferroelectric-to-paraelectric phase transitions with remarkably high Curie temperature of up to 505 K, superior to most of molecular ferroelectrics. Moreover, the covalent bonding between phosphorescent organic component and the light-harvesting inorganic component achieves efficient spin-orbit coupling and intersystem crossing, resulting in long-lived afterglow emission. The compelling combination of high stability, ferroelectricity and afterglow emission exhibited by lead halide MOFs opens up many potential opportunities in energy-conversion applications.

Achieving Dual Emission of Fluorescence and Phosphorescence from Anti-Kasha's Metal-Organic Halides for Information Encryption

Luminescent materials typically emit their fluorescence or phosphorescence at a specific wavelength with different excitation energies via the so-called Kasha's rule. If fluorescence or phosphorescence emission via anti-Kasha's rule could be achieved, it will hold great promise for applications in many fields. In this work, we report the synthesis and characterization of new metal-organic halide materials with dual emission of efficient room-temperature phosphorescence and fluorescence, which obey anti-Kasha's rule. Here, three emitting metal-organic halides with formula [ZnX2(bidpe)] (X = Cl for 1, X = Br for 2, X = I for 3, bidpe = 4,4'-bis(imidazol-1-yl)diphenyl ether) were prepared and their photophysical properties were investigated. The complexes exhibit dual emission of fluorescence and phosphorescence via anti-Kasha's rule, and their RTP properties of resultant products are modulated by halide substitution synthesis. DFT calculations indicate that the singlet states exhibit a halide-ligand charge transfer (XLCT) character while the triplet states are dominated by the intraligand π-π* transitions. Furthermore, the multilevel information encryption and anticounterfeiting applications are developed by virtue of anti-Kasha's rule emission.

Phosphine Oxide-Nd3+ Coordination Chains with Cumulated Output Enable Efficient LED-Pumping Optical Amplification

Near-infrared luminescent rare-earth organic complexes have attracted intensive attention in the field of optical waveguide amplification. However, their optical gains were commonly less than 4 dB/cm due to limited doping concentrations. Herein, two one-dimensional (1D) Nd3+ coordination chains, namely, [Nd(TTA)3(DBTDPO)]n (Nd1) and [Nd(TTA)3(DPEPO)]n (Nd2), bridged by phosphine oxide ligands were developed for the neodymium-doped waveguide amplifier. Despite its P-P distance being similar to DBTDPO, the different P═O orientation of DPEPO renders markedly shorter intra- and interchain Nd-Nd distances for Nd2 in comparison to Nd1. Furthermore, the weaker intermolecular interactions alleviate the quenching effect for Nd2. Therefore, Nd2 can provide more locally concentrated and radiative Nd3+ ions, leading to a larger Nd3+-characteristic 1.06 μm emission intensity and duration than Nd1. Based on embedded and evanescent-field waveguide structures, Nd2 achieves state-of-the-art gain maxima of 5.7 and 4.9 dB/cm as well as outstanding gain stability. These results indicate that controllable coordination assembly of lanthanide ions in multidimension provides a flexible approach to combine local high-density outputs and effective suppression of quenching.

Optical Phenomena in Molecule-Based Magnetic Materials

Since the last century, we have witnessed the development of molecular magnetism which deals with magnetic materials based on molecular species, i.e., organic radicals and metal complexes. Among them, the broadest attention was devoted to molecule-based ferro-/ferrimagnets, spin transition materials, including those exploring electron transfer, molecular nanomagnets, such as single-molecule magnets (SMMs), molecular qubits, and stimuli-responsive magnetic materials. Their physical properties open the application horizons in sensors, data storage, spintronics, and quantum computation. It was found that various optical phenomena, such as thermochromism, photoswitching of magnetic and optical characteristics, luminescence, nonlinear optical and chiroptical effects, as well as optical responsivity to external stimuli, can be implemented into molecule-based magnetic materials. Moreover, the fruitful interactions of these optical effects with magnetism in molecule-based materials can provide new physical cross-effects and multifunctionality, enriching the applications in optical, electronic, and magnetic devices. This Review aims to show the scope of optical phenomena generated in molecule-based magnetic materials, including the recent advances in such areas as high-temperature photomagnetism, optical thermometry utilizing SMMs, optical addressability of molecular qubits, magneto-chiral dichroism, and opto-magneto-electric multifunctionality. These findings are discussed in the context of the types of optical phenomena accessible for various classes of molecule-based magnetic materials.

Robust luminogens as cutting-edge tools for efficient light emission in recent decades

Blue luminogens play a vital role in white lighting and potential metal-free fluorescent materials and their high-lying excited states contribute to harvesting triplet excitons in devices. However, in TADF-OLEDs (ΔEST < 0.1 eV), although T1 excitons transfer to S1via RISC with 100% IQE, the longer lifetime of blue TADF suffers from efficiency roll-off (RO). In this case, hybridized local and charge transfer (HLCT) materials have attracted significant interest in lighting owing to their 100% hot exciton harvesting and enhanced efficiency. Both academics and industrialists widely use the HLCT strategy to improve the efficiency of fluorescent organic light-emitting diodes (FOLEDs) by harvesting dark triplet excitons through the RISC process. Aggregation-induced emissive materials (AIEgens) possess tight packing in the aggregation state, and twisted AIEgens with HLCT behaviour have a shortened conjugation length, inducing blue emission and making them suitable candidates for OLED applications. TTA-OLEDs are used in commercial BOLEDs because of their moderate efficiency and reasonable operation lifetime. In this review, we discuss the devices based on TTA fluorophores, TADF fluorophores, HLCT fluorophores, AIEgens and HLCT-sensitized fluorophores (HLCT-SF), which break through the statistical limitations.

Bicarbazole-Benzophenone Based Twisted Donor-Acceptor Derivatives as Potential Blue TADF Emitters for OLEDs

Over the past few decades, organic light-emitting diodes (OLEDs) find applications in smartphones, televisions, and the automotive sector. However, this technology is still not perfect, and its application for lighting purposes has been slow. For further development of the OLEDs, we designed twisted donor-acceptor-type electroactive bipolar derivatives using benzophenone and bicarbazole as building blocks. Derivatives were synthesized through the reaction of 4-fluorobenzophenone with various mono-alkylated 3,3'-bicarbazoles. We have provided a comprehensive structural characterization of these compounds. The new materials are amorphous and exhibit suitable glass transition temperatures ranging from 57 to 102 °C. They also demonstrate high thermal stability, with decomposition temperatures reaching 400 °C. The developed compounds exhibit elevated photoluminescence quantum yields (PLQY) of up to 75.5% and favourable HOMO-LUMO levels, along with suitable triplet-singlet state energy values. Due to their good solubility and suitable film-forming properties, all the compounds were evaluated as blue TADF emitters dispersed in commercial 4,4'-bis(N-carbazolyl)-1,10-biphenyl (CBP) host material and used for the formation of emissive layer of organic light-emitting diodes (OLEDs) in concentration-dependent experiments. Out of these experiments, the OLED with 15 wt% of the emitting derivative 4-(9'-{2-ethylhexyl}-[3,3']-bicarbazol-9-yl)benzophenone exhibited superior performance. It attained a maximum brightness of 3581 cd/m2, a current efficacy of 5.7 cd/A, a power efficacy of 4.1 lm/W, and an external quantum efficacy of 2.7%.

Dynamic Room Temperature Phosphorescence of Silane-Functionalized Carbon Dots Confining within Silica for Anti-Counterfeiting Applications

Room temperature phosphorescent (RTP) materials with long-lived, excitation-dependent, and time-dependent phosphorescence are highly desirable but very hard to achieve. Herein, this work reports a rational strategy of multiple wavelength excitation and time-dependent dynamic RTP color by confining silane-functionalized carbon dots (CDs) in a silica matrix (Si-CDs@SiO2). The Si-CDs@SiO2 possesses unique green-light-excitation and a change in phosphorescence color from yellow to green. A slow-decaying phosphorescence at 500 nm with a lifetime of 1.28 s and a fast-decaying phosphorescence at 580 nm with a lifetime of 0.90 s are observed under 365 nm of irradiation, which originated from multiple surface triplet states of the Si-CDs@SiO2. Given the unique dynamic RTP properties, the Si-CDs@SiO2 are demonstrated for applications in fingerprint recognition and multidimensional dynamic information encryption. These findings will open an avenue to explore dynamic phosphorescent materials and significantly broaden their applications.

A cyclometalated Pt(II)-Pt(II) clamshell dimer with a triplet emission at 887 nm

Here, a cyclometalated Pt(II) clamshell dimer (complex 2) has been synthesized with the primary ligand of dibenzo(f,h)quinoxaline and an ancillary ligand of N,N'-diphenylformamidine. In addition, a mononuclear Pt(II) complex 1a and a binuclear Pt(II) complex 1b were also prepared. Complex 1a was coordinated by one cyclometalated ligand of dibenzo(f,h)quinoxaline, one chloride ion, and one N,N'-diphenylformamidine. Complex 1b was coordinated by one cyclometalated ligand of dibenzo(f,h)quinoxaline, two chloride ions, and two N,N'-diphenylformamidines. All of these three complexes were characterized by nuclear magnetic resonance (NMR) spectroscopy, high-resolution mass spectrometry (HRMS), elemental analyses, and single-crystal X-ray diffraction (XRD). The Pt-Pt distance in complex 2 was 2.8439(2) Å. It also exhibited a near-infrared (near-IR) emission at 887 nm in the pure solid state. On the other hand, complexes 1a and 1b exhibited triplet emission at 589 and 660 nm, respectively, in the pure solid state. Furthermore, in 2 wt% poly(Me methacrylate) (PMMA) films, complex 1a showed a triplet emission at 548 nm (with Φ = 84% and τ = 5.53 μs) and complex 1b showed an emission at 627 nm (with Φ = 79% and τ = 4.07 μs). Due to its great photophysical properties, complex 1b was deposited onto quartz plates for the detection of organic solvent vapors and it showed unique emission quenching for the vapor of tetrahydrofuran.

One Dianionic Luminophore with Three Coordination Modes Binding Four Different Metals: Toward Unexpectedly Phosphorescent Transition Metal Complexes

This work reports on a battery of coordination compounds featuring a versatile dianionic luminophore adopting three different coordination modes (mono, bi, and tridentate) while chelating Pd(II), Pt(II), Au(III), and Hg(II) centers. An in-depth structural characterization of the ligand precursor (H2 L) and six transition metal complexes ([HLPdCNtBu], [LPtCl], [LPtCNtBu], [LPtCNPhen], [HLHgCl], and [LAuCl]) is presented. The influence of the cations and coordination modes of the luminophore and co-ligands on the photophysical properties (including photoluminescence quantum yields (ΦL ), excited state lifetimes (τ), and average (non-)radiative rate constants) are evaluated at various temperatures in different phases. Five complexes show interesting photophysical properties at room temperature (RT) in solution. Embedment in frozen glassy matrices at 77 K significantly boosts their luminescence by suppressing radiationless deactivation paths. Thus, the Pt(II)-based compounds provide the highest efficiencies, with slight variations upon exchange of the ancillary ligand. In the case of [HLPdCNtBu], both ΦL and τ increase over 30-fold as compared to RT. Furthermore, the Hg(II) complex achieves, for the first time in its class, a ΦL exceeding 60% and millisecond-range lifetimes. This demonstrates that a judicious ligand design can pave the way toward versatile coordination compounds with tunable excited state properties.

Side group dependent room temperature crystallization-induced phosphorescence of benzil based all organic phosphors

In this work, we report alkoxy substituted benzil based all organic room temperature phosphors which showed crystallization induced phosphorescence (CIP). Nine title compounds were prepared with various alkyl lengths (OCnH2n+1: n = 8-16) and the effect of alkyl side group length on the phosphorescence performance was investigated, as compared to p-anisil. It was found that both phosphorescence quantum yield and lifetime increased concomitantly as the alkyl length increased up to nonyloxy (BZL-OC9). Further increase in the carbon number caused the phosphorescence performance to deteriorate due to greater conformational freedom of the side groups. An incredible quantum yield of 70% was achieved for BZL-OC9. A promising finding is that the increased quantum yield was accompanied by the increase in the lifetime relative to p-anisil, which has been historically challenging. Single crystallography coupled with UV-Vis spectroscopy revealed that a higher level of intermolecular π-π interactions was observed from p-anisil while more alkyl interactions with less intermolecular π-orbital overlap were found for BZL-OC8. As a result, molecular rigidification with less phosphorescence quenching was achieved for BZL-OC8 leading to enhanced performance. A precipitation study on a dichloromethane solution as a function of the content of MeOH (poor solvent) proved that the emission of the BZL-OCn system is truly aggregation-induced. The current work demonstrates that strategic side group engineering could be a promising approach to developing high-performance all organic phosphors as well as improving the properties of existing phosphors.

A Review of Benzophenone-Based Derivatives for Organic Light-Emitting Diodes

Organic light-emitting diodes (OLEDs) have garnered considerable attention in academic and industrial circles due to their potential applications in flat-panel displays and solid-state lighting technologies, leveraging the advantages offered by organic electroactive derivatives over their inorganic counterparts. The thin and flexible design of OLEDs enables the development of innovative lighting solutions, facilitating the creation of customizable and contoured lighting panels. Among the diverse electroactive components employed in the molecular design of OLED materials, the benzophenone core has attracted much attention as a fragment for the synthesis of organic semiconductors. On the other hand, benzophenone also functions as a classical phosphor with high intersystem crossing efficiency. This characteristic makes it a compelling candidate for effective reverse intersystem crossing, with potential in leading to the development of thermally activated delayed fluorescent (TADF) emitters. These emitting materials witnessed a pronounced interest in recent years due to their incorporation in metal-free electroactive frameworks and the capability to convert triplet excitons into emissive singlet excitons through reverse intersystem crossing (RISC), consequently achieving exceptionally high external quantum efficiencies (EQEs). This review article comprehensively overviews the synthetic pathways, thermal characteristics, electrochemical behaviour, and photophysical properties of derivatives based on benzophenone. Furthermore, we explore their applications in OLED devices, both as host materials and emitters, shedding light on the promising opportunities that benzophenone-based compounds present in advancing OLED technology.

Mononuclear indium(III) photosensitizers for photo-dehalogenation and olefin reduction

Photoactive main-group complexes have been relatively underexplored in photocatalytic applications. Herein, we report a family of indium(III) complexes (In-1-In-4) containing pyridylpyrrolide ligands with different amounts of methyl groups, which all exhibit intense visible-light absorption as well as blue-green emission with nanosecond emission lifetimes and emission quantum yields of 6.7-12.5%. Electrochemical studies and quantum chemical calculations indicate that their (photo-)redox processes involve only ligand-centered events, which efficiently mediate photocatalytic dehalogenation and olefin reduction.

Recent progress in multi-resonance thermally activated delayed fluorescence emitters with an efficient reverse intersystem crossing process

Multi-resonance thermally activated delayed fluorescence (MR-TADF) emitters have become an active research topic at the forefront of organic light-emitting diodes (OLEDs) owing to their excellent photophysical properties such as high efficiency and narrow emission characteristics. However, MR-TADF materials always exhibit slow reverse intersystem crossing rates (kRISC) due to the large energy gap and small spin-orbit coupling values between singlet and triplet excited states. In order to optimize the RISC process, strategies such as heavy-atom-integration, metal perturbation, π-conjugation extension and peripheral decoration of donor/acceptor units have been proposed to construct efficient MR-TADF materials for high-performance OLEDs. This article provides an overview of the recent progress in MR-TADF emitters with an efficient RISC process, focusing on the structure-activity relationship between the molecular structure, optoelectronic feature, and OLED performance. Finally, the potential challenges and future prospects of MR-TADF materials are discussed to gain a more comprehensive understanding of the opportunities for efficient narrowband OLEDs.

Design of luminescent complexes with different Cu4I4 cores based on pyridyl phenoxarsines

A series of luminescent Cu4I4 clusters with stair-step, cubane, and octahedral geometries supported by a novel type of cyclic As,N-ligand, pyridyl-containing 10-phenoxarsines, were synthesized and characterized by NMR spectroscopy, mass spectrometry, elemental analysis, and single-crystal X-ray diffraction analysis. An unusual arrangement of As,N-bidentate and μ2-iodo ligands was found in the octahedral cluster. The structural diversity of the Cu(I) complexes is reflected in their photophysical properties: the phosphorescence spectra of the compounds display emission in a broad spectral range of 495-597 nm. The complex with the Cu4I4L2 stoichiometry bearing a stair-step Cu4I4 core demonstrates temperature-dependent dual emission. The luminescence properties of all complexes were rationalized by DFT calculations.

Adsorption and photocatalytic applications of porphyrin-based materials for environmental separation processes: A review

As society progresses and industrializes, the issue of water pollution, caused by a wide array of organic and inorganic pollutants, poses significant risks to both human well-being and the environment. Given its distinctive characteristics, water pollution has become a paramount concern for society, necessitating immediate attention. Numerous studies have been conducted on wastewater treatment, primarily focusing on two key approaches: adsorption and photocatalytic degradation. Adsorption offers unparalleled advantages, including its simplicity, high removal efficiency, and cost-effectiveness. Conversely, photocatalysis harnesses abundant, clean, and non-polluting sunlight, addressing the critical issue of energy scarcity. Porphyrins, which are macrocyclic tetrapyrrole derivatives found widely in nature, have attracted growing interest in recent years. These lipophilic pigments exhibit remarkable chemical stability and have retained their major structural features for up to 1.1 billion years. As such, they are considered vital indicators of life and have been extensively studied, from the remnants of extinct organisms to gain insights into the principles of evolution. Porphyrins are often associated with a central metal ion within their ring system and can be modified through various substituents, including additional rings or ring opening, resulting in a wide range of functionalities. This comprehensive review summarizes recent advancements in the field of porphyrins. It begins by introducing the structures and preparation methods of porphyrins. Subsequently, it delves into notable applications of porphyrins in the context of pollutant adsorption in water and their environmentally friendly photocatalytic degradation.

Recent Advances in Functional Materials for Optical Data Storage

In the current data age, the fundamental research related to optical applications has been rapidly developed. Countless new-born materials equipped with distinct optical properties have been widely explored, exhibiting tremendous values in practical applications. The optical data storage technique is one of the most significant topics of the optical applications, which is considered as the prominent solution for conquering the challenge of the explosive increase in mass data, to achieve the long-life, low-energy, and super high-capacity data storage. On this basis, our review outlines the representative reports for mainly introducing the functional systems based on the newly established materials applied in the optical storage field. According to the material categories, the representative functional systems are divided into rare-earth doped nanoparticles, graphene, and diarylethene. In terms of the difference of structural features and delicate properties among the three materials, the application in optical storage is comprehensively illustrated in the review. Meanwhile, the potential opportunities and critical challenges of optical storage are also discussed in detail.

The afterglow of carbon dots shining in inorganic matrices

Carbon dots (CDs) are a new type of quasi-spherical and zero-dimension carbon nanomaterial with a diameter less than 10 nm. They exhibit a broad absorption spanning from the ultraviolet (UV) to visible light regions and inspire growing interests due to their excellent performance. In recent years, it was identified that the CDs embedded in various inorganic matrices (IMs) can effectively activate afterglow emission by suppressing the nonradiative transitions of molecules and protecting the triplet excitons of CDs, which hold broad application prospects. Herein, recent advances in CDs@IMs are reviewed in detail, and the interaction and luminescence mechanisms between CDs and IMs are also summarized. We highlight the synthetic strategies of constructing composites and the roles of IMs in facilitating the applications of CDs in diverse areas. Finally, some directions and challenges of future research in this field are proposed.

Coordination-assembled phosphorescent microstructure from RTP HOF and Eu3+-doping ZGO:Mn phosphors for cancer biomarker amplification detection and information encryption

The ultra-long room temperature phosphorescent hydrogen-bonded organic framework (RTP HOF) materials can achieve long afterglow via ligand hydrogen bond interaction and water implement to suppress the non-radiative decays by matrices rigidification, and its electron donor conjugated structure is first developed as a phosphorescent quencher. The Eu3+/Mn2+ co-doped Zn2GeO4 phosphors (ZGO:Mn, Eu) with abundant metal sites and enhanced phosphorescence were synthesized as response factors and electron acceptors, combined with RTP HOFs to form microstructures featuring multi-color modulation, as an high-level anti-counterfeiting platform and lysophosphatidic acid (LPA) detection unit. LPA is an ideal plasma biomarker for early diagnosis of ovarian and other gynecologic cancers. This detection strategy relies on the differential coordination substitution to restore ZGO:Mn, Eu phosphorescence through synergistic coordination of LPA and the hydrophobic assistance of LPA, and dual functional groups identification of LPA achieve specific detection at the nanomolar level. The anti-counterfeiting platform can fetch specific information by controlling the afterglow distinction and excited light from ZGO:Mn, Eu and RTP HOF. This study not only provides a typical case of the preparation of two phosphors with heterogeneous optical properties, but also expands the application field of combined phosphors as intelligent luminescent materials.

Organic Excitonic State Management by Surface Metallic Coupling of Inorganic Lanthanide Nanocrystals

The ability to harness charges and spins for control of organic excitonic states is critical in developing high-performance organic luminophores and optoelectronic devices. Here we report a facile strategy to efficiently manipulate the electronic energy states of various organic phosphors by coupling them with inorganic lanthanide nanocrystals. We show that the metallic atoms exposed on the nanocrystal surface can introduce strong coupling effects to 9-(4-ethoxy-6-phenyl-1,3,5-triazin-2-yl)-9H-carbazole (OCzT) and some organic chromophores with carbazole functional groups when the organics are approaching the nanocrystals. This unconventional organic-inorganic hybridization enables a nearly 100 % conversion of the singlet excitation to fast charge transfer luminescence that does not exist in pristine organics, which broadens the utility of organic phosphors in hybrid systems.

Aptamer-Protein Interactions: From Regulation to Biomolecular Detection

Serving as the basis of cell life, interactions between nucleic acids and proteins play essential roles in fundamental cellular processes. Aptamers are unique single-stranded oligonucleotides generated by in vitro evolution methods, possessing the ability to interact with proteins specifically. Altering the structure of aptamers will largely modulate their interactions with proteins and further affect related cellular behaviors. Recently, with the in-depth research of aptamer-protein interactions, the analytical assays based on their interactions have been widely developed and become a powerful tool for biomolecular detection. There are some insightful reviews on aptamers applied in protein detection, while few systematic discussions are from the perspective of regulating aptamer-protein interactions. Herein, we comprehensively introduce the methods for regulating aptamer-protein interactions and elaborate on the detection techniques for analyzing aptamer-protein interactions. Additionally, this review provides a broad summary of analytical assays based on the regulation of aptamer-protein interactions for detecting biomolecules. Finally, we present our perspectives regarding the opportunities and challenges of analytical assays for biological analysis, aiming to provide guidance for disease mechanism research and drug discovery.

Understanding the degradation mechanism of TTA-based blue fluorescent OLEDs by exciton dynamics and transient electroluminescence measurements

The lifetime of blue organic light-emitting diodes (OLEDs) has always been a big challenge in practical applications. Blue OLEDs based on triplet-triplet annihilation (TTA) up-conversion materials have potential to achieve long lifetimes due to fusing two triplet excitons to one radiative singlet exciton, but there is a lack of an in-depth understanding of exciton dynamics on degradation mechanisms. In this work, we established a numerical model of exciton dynamics to study the impact factors in the stability of doped blue OLEDs based on TTA up-conversion hosts. By performing transient electroluminescence experiments, the intrinsic parameters related to the TTA up-conversion process of aging devices were determined. By combining the change of excess charge density in the emitting layer (EML) with aging time, it is concluded that the TTA materials are damaged by the excess electrons in the EML during ageing, which is the main degradation mechanism of OLEDs. This work provides a theoretical basis for preparing long-lifetime blue fluorescent OLEDs.

Phosphine-Oxide-Balanced Intra- and Interchain Through-Space Charge Transfer in Thermally Activated Delayed Fluorescence Polymers: Beyond 30% External Quantum Efficiency

Through-space charge transfer (TSCT) is crucial for developing highly efficient thermally activated delayed fluorescence polymers. The balance of intra- and interchain TSCT can markedly improve performance, but it is still a big challenge. In this work, an effective strategy for "intra- and interchain TSCT balance" is demonstrated by way of a series of non-conjugated copolymers containing a 9,9-dimethylacridine donor and triazine-phosphine oxide (PO)-based acceptors. Steady-state and transient emission spectra indicate that compared to the corresponding blends, the copolymers can indeed achieve balanced intra- and interchain TSCT by accurately optimizing the inductive and steric effects of the acceptors. The DPOT acceptor with the strongest electron-withdrawing ability and the second bigger steric hindrance endows its copolymers with state-of-the-art photoluminescence and electroluminescence quantum efficiencies beyond 95% and 32%, respectively. This demonstrates that, compared to other congeners, the synergistic inductive and steric effects effectively enhance TSCT in DPOT-based copolymers for radiation, and suppress singlet and triplet quenching. The record-high efficiencies of its devices make this kind of copolymers hold the potential for low-cost, large-scale, and high-efficiency applications.

Interfacial Passivation Enormously Enhances Electroluminescence of Triphenylphosphine Cu4 I4 Cube

Defect is one of the key factors limiting optoelectronic performances of organic-inorganic hybrid systems. Although high-efficiency bidentate ligands based electroluminescent (EL) clusters reported, until present, only few EL clusters based on monodentate ligands are realized since their structural instability induces more surface/interface defects. Herein, this bottleneck is first overcome in virtue of interfacial passivation by electron transporting layers (ETL). Through using TmPyPB with meta-linked pyridines as ETL, photoluminescent (PL) and EL quantum efficiencies of the simplest monophosphine Cu4 I4 cube [TPP]4 Cu4 I4 are greatly improved by ≈2 and 23 folds, respectively, as well as ≈200 folds increased luminance, corresponding to a huge leap from nearly unlighted (<20 nits) to highly bright (>3000 nits). The passivation effect of TmPyPB on surface defects of cluster layer is embodied as preventing interfacial charge trapping and suppressing exciton nonradiation.

Abd A. Photo Stabilizing Efficiency Of Poly(methyl methacrylate) Based On Metal Ion Complexes Of Saccharine

The photostabilization of poly(methyl methacrylate) (PMMA) films having saccharine complexes of Zn(II), Cd(II), Hg(II), Fe(III), Ni(II) and Cu(II) complexes was investigated. The production of PMMA films containing such complexes (0.5% by weight) was carried out by the casting method using THF. The photostabilization activities of the compounds were determined by monitoring the carbonyl and hydroxyl index with irradiation time. Evaluation of stabilizing efficiency of PMMA by ultra-violet spectroscopy to investigate photodecomposition rate constant (kd) for PMMA films in the absence and presence of saccharine complexes. The changes in the viscosity average molecular weight of PMMA with irradiation time were evaluated. The rate of photostabilization for PMMA in the presence of the additives was found to follow the order Ni(sac) > Cu(sac) > Zn(sac) > Cd(sac) > Hg(sac) > Fe(sac). Depending on the structure of the additive, such as a peroxide decomposer, UV absorption or a radical scavenger for the photostabilizer. Keywords: Photodegradation, UV stabilizers, PMMA, Saccharine.

cis/trans-[Pt(C∧N)(C≡CR)(CNBut)] Isomers: Synthesis, Photophysical, DFT Studies, and Chemosensory Behavior

cis/trans Isomerism can be a crucial factor for photophysical properties. Here, we report the synthesis and optical properties of a series of trans- and cis-alkynyl/isocyanide cycloplatinated compounds [Pt(C^∧N)(C≡CR)(CNBu^t)] [R = C₆H₄-4-OMe 1, 3-C₄H₃S 2; C^∧N = 2-(2,4-difluorophenyl)pyridine (dfppy) (a), 4-(2-pyridyl)benzaldehyde (ppy-CHO) (b)]. The trans-forms do not isomerize thermally in MeCN solution to the cis forms, but upon photochemical irradiation in this medium at 298 K, a variable isomerization to the cis forms was observed. This behavior is in good agreement with the theoretically calculated energy values. The trans/cis configuration, the identity of the cyclometalated, and the alkynyl ligand influence on the absorption and emission properties of the complexes in solution, polystyrene (PS) films, and solid state are reported. All complexes are efficient triplet emitters in all media (except for trans-1a and trans-2a in CH₂Cl₂ solution at 298 K), with emission wavelengths depending mainly on the cyclometalated ligand in the region 473-490 nm (dfppy), 510-550 (ppy-CHO), and quantum yields (ϕ) ranging from 18.5 to 40.7% in PS films. The combined photophysical data and time-dependent density functional theory calculations (TD-DFT) at the excited-state T₁ geometry reveal triplet excited states of ³L'LCT (C≡CR → C^∧N)/³IL (C^∧N) character with minor ³MLCT contribution. The dfppy (a) complexes show a greater tendency to aggregate in rigid media than the ppy-CHO (b) and the cis with respect to the trans, showing red-shifted structureless bands of ³MMLCT and/or excimer-like nature. Interestingly, trans-1a,2a and cis-1a,2a undergo significant changes in the ultraviolet (UV) and emission spectra with Hg²⁺ ions enabling their use for sensing of Hg²⁺ ions in solution. This is clearly shown by the hypsochromic shift and substantial decrease of the low-energy absorption band and an increase of the intensity of the emission in the MeCN solution upon the addition of a solution of Hg(ClO₄)₂ (1:5 molar ratio). Job's plot analysis estimated a 1:1 stoichiometry in the complexation mode of Hg²⁺ by trans-2a. The binding constant (log K) calculated for this system from absorption titration data resulted to be 2.56, and the limit of the detection (LOD) was 6.54 × 10^-7 M.

A Feasible Strategy for a Highly Efficient Thermally Activated Delayed Fluorescence Emitter Over 900 nm Based on Phenalenone Derivatives

Near-infrared (NIR) organic light-emitting diodes (OLEDs) suffer from the low external electroluminescence (EL) quantum efficiency (EQE), which is a critical obstacle for potential applications. Herein, 1-oxo-1-phenalene-2,3-dicarbonitrile (OPDC) is employed as an electron-withdrawing aromatic ring, and by incorporating with triphenylamine (TPA) and biphenylphenylamine (BBPA) donors, two novel NIR emitters with thermally activated delayed fluorescence (TADF) characteristics, namely OPDC-DTPA and OPDC-DBBPA, are first developed and compared in parallel. Intense NIR emission peaks at 962 and 1003 nm are observed in their pure films, respectively. Contributed by the local excited (LE) characteristics in the triplet (T1 ) state in synergy with the charge transfer (CT) characteristics for the singlet (S1 ) state to activate TADF emission, the solution processable doped NIR OLEDs based on OPDC-DTPA and OPDC-DBBPA yield EL peaks at 834 and 906 nm, accompanied with maximum EQEs of 0.457 and 0.103 %, respectively, representing the state-of-the-art EL performances in the TADF emitter-based NIR-OLEDs in the similar EL emission regions so far. This work manifests a simple and effective strategy for the development of NIR TADF emitters with long wavelength and efficiency synchronously.

Pendant Modification of Poly(methyl methacrylate) to Enhance Its Stability against Photoirradiation

Photostabilization of functional polymeric materials is important for protection against aging and ultraviolet (UV) irradiation. There is, therefore, the impetus to modify polymers to increase their resistance to photodegradation and photooxidation on extended exposure to UV light in harsh conditions. Various polymeric additives have been designed and synthesized in recent years, and their potential as photostabilizers has been explored. Reported here is the effect of pendant functionalization of poly(methyl methacrylate) (PMMA) through organometallic moiety incorporation into the polymer's backbone. The reaction of PMMA with ethylenediamine leads to the formation of an amino residue that can react with salicylaldehyde to produce the corresponding Schiff base. Adding metal chlorides (zinc, copper, nickel, and cobalt) led to the formation of organometallic residues on the polymeric chains. Thin films of modified and unmodified PMMA were produced and irradiated with UV light to determine the effect of pendant modification on photostability. The photostabilization of PMMA was assessed using a range of methods, including infrared spectroscopy, weight loss, decomposition rate constant, and surface morphology. The modified PMMA incorporating organic Schiff base metal complexes showed less photodecomposition than the unmodified polymer or one containing the Schiff base only. Thus, the metals significantly reduced the photodegradation of polymeric materials. The polymer containing the Schiff base-cobalt unit showed the least damage in the PMMA surface due to photoirradiation, followed by those containing nickel, zinc, and copper, in that order.

Competition between N,C,N-Pincer and N,N-Chelate Ligands in Platinum(II)

Replacement of the chloride ligand of PtCl{κ3-N,C,N-[py-C6HR2-py]} (R = H (1), Me (2)) and PtCl{κ3-N,C,N-[py-O-C6H3-O-py]} (3) by hydroxido gives Pt(OH){κ3-N,C,N-[py-C6HR2-py]} (R = H (4), Me (5)) and Pt(OH){κ3-N,C,N-[py-O-C6H3-O-py]} (6). These compounds promote deprotonation of 3-(2-pyridyl)pyrazole, 3-(2-pyridyl)-5-methylpyrazole, 3-(2-pyridyl)-5-trifluoromethylpyrazole, and 2-(2-pyridyl)-3,5-bis(trifluoromethyl)pyrrole. The coordination of the anions generates square-planar derivatives, which in solution exist as a unique species or equilibria between isomers. Reactions of 4 and 5 with 3-(2-pyridyl)pyrazole and 3-(2-pyridyl)-5-methylpyrazole provide Pt{κ3-N,C,N-[py-C6HR2-py]}{κ1-N1-[R'pz-py]} (R = H; R' = H (7), Me (8). R = Me; R' = H (9), Me (10)), displaying κ1-N1-pyridylpyrazolate coordination. A 5-trifluoromethyl substituent causes N1-to-N2 slide. Thus, 3-(2-pyridyl)-5-trifluoromethylpyrazole affords equilibria between Pt{κ3-N,C,N-[py-C6HR2-py]}{κ1-N1-[CF3pz-py]} (R = H (11a), Me (12a)) and Pt{κ3-N,C,N-[py-C6HR2-py]}{κ1-N2-[CF3pz-py]} (R = H (11b), Me (12b)). 1,3-Bis(2-pyridyloxy)phenyl allows the chelating coordination of the incoming anions. Deprotonations of 3-(2-pyridyl)pyrazole and its substituted 5-methyl counterpart promoted by 6 lead to equilibria between Pt{κ3-N,C,N-[pyO-C6H3-Opy]}{κ1-N1-[R'pz-py]} (R' = H (13a), Me (14a)) with a κ-N1-pyridylpyrazolate anion, keeping the pincer coordination of the di(pyridyloxy)aryl ligand, and Pt{κ2-N,C-[pyO-C6H3(Opy)]}{κ2-N,N-[R'pz-py]} (R' = H (13c), Me (14c)) with two chelates. Under the same conditions, 3-(2-pyridyl)-5-trifluoromethylpyrazole generates the three possible isomers: Pt{κ3-N,C,N-[pyO-C6H3-Opy]}{κ1-N1-[CF3pz-py]} (15a), Pt{κ3-N,C,N-[pyO-C6H3-Opy]}{κ1-N2-[CF3pz-py]} (15b), and Pt{κ2-N,C-[pyO-C6H3(Opy)]}{κ2-N,N-[CF3pz-py]} (15c). The N1-pyrazolate atom produces a remote stabilizing effect on the chelating form, pyridylpyrazolates being better chelate ligands than pyridylpyrrolates. Accordingly, reactions of 4-6 with 2-(2-pyridyl)-3,5-bis(trifluoromethyl)pyrrole yield Pt{κ3-N,C,N-[py-C6HR2-py]}{κ1-N1-[(CF3)2C4(py)HN]} (R = H (16), Me (17)) or Pt{κ3-N,C,N-[pyO-C6H3-Opy]}{κ1-N1-[(CF3)2C4(py)HN]} (18), displaying κ1-N1-pyrrolate coordination. Complexes 7-10 are efficient green phosphorescent emitters (488-576 nm). In poly(methyl methacrylate) (PMMA) films and in dichloromethane, they experience self-quenching, due to molecular stacking. Aggregation occurs through aromatic π-π interactions, reinforced by weak platinum-platinum interactions.

Organometallic Intermediates in the Synthesis of Photoluminescent Zirconium and Hafnium Complexes with Pyridine Dipyrrolide Ligands

The two commercially available zirconium complexes tetrakis(dimethylamido)zirconium, Zr(NMe2)4, and tetrabenzylzirconium, ZrBn4, were investigated for their utility as starting materials in the synthesis of bis(pyridine dipyrrolide)zirconium photosensitizers, Zr(PDP)2. Reaction with one equivalent of the ligand precursor 2,6-bis(5-methyl-3-phenyl-1H-pyrrol-2-yl)pyridine, H2MePDPPh, resulted in the isolation and structural characterization of the complexes (MePDPPh)Zr(NMe2)2thf and (MePDPPh)ZrBn2, which could be converted to the desired photosensitizer Zr(MePDPPh)2 upon addition of a second equivalent of H2MePDPPh. Using the more sterically encumbered ligand precursor 2,6-bis(5-(2,4,6-trimethylphenyl)-3-phenyl-1H-pyrrol-2-yl)pyridine, H2MesPDPPh, only ZrBn4 yielded the desired bis-ligand complex Zr(MesPDPPh)2. Careful monitoring of the reaction at different temperatures revealed the importance of the organometallic intermediate (cyclo-MesPDPPh)ZrBn, which was characterized by X-ray diffraction analysis and 1H NMR spectroscopy and shown to contain a cyclometalated MesPDPPh unit. Taking inspiration from the results for zirconium, syntheses for two hafnium photosensitizers, Hf(MePDPPh)2 and Hf(MesPDPPh)2, were established and shown to proceed through similar intermediates starting from tetrabenzylhafnium, HfBn4. Initial studies of the photophysical properties of the photoluminescent hafnium complexes indicate similar optical properties compared to their zirconium analogues.

Bifunctional Bicarbazole-Benzophenone-Based Twisted Donor-Acceptor-Donor Derivatives for Deep-Blue and Green OLEDs

Organic light-emitting diodes (OLEDs) have played a vital role in showing tremendous technological advancements for a better lifestyle, due to their display and lighting technologies in smartphones, tablets, television, and automotive industries. Undoubtedly, OLED is a mainstream technology and, inspired by its advancements, we have designed and synthesized the bicarbazole-benzophenone-based twisted donor-acceptor-donor (D-A-D) derivatives, namely DB13, DB24, DB34, and DB43, as bi-functional materials. These materials possess high decomposition temperatures (>360 °C) and glass transition temperatures (~125 °C), a high photoluminescence quantum yield (>60%), wide bandgap (>3.2 eV), and short decay time. Owing to their properties, the materials were utilized as blue emitters as well as host materials for deep-blue and green OLEDs, respectively. In terms of the blue OLEDs, the emitter DB13-based device outperformed others by showing a maximum EQE of 4.0%, which is close to the theoretical limit of fluorescent materials for a deep-blue emission (CIEy = 0.09). The same material also displayed a maximum power efficacy of 45 lm/W as a host material doped with a phosphorescent emitter Ir(ppy)3. Furthermore, the materials were also utilized as hosts with a TADF green emitter (4CzIPN) and the device based on DB34 displayed a maximum EQE of 11%, which may be attributed to the high quantum yield (69%) of the host DB34. Therefore, the bi-functional materials that are easily synthesized, economical, and possess excellent characteristics are expected to be useful in various cost-effective and high-performance OLED applications, especially in displays.

Designing a new method for growing metal-organic framework (MOF) on MOF: synthesis, characterization and catalytic applications

Metal-organic frameworks as a unique class of high-surface-area materials have gained considerable attention due to their characteristic properties. In this perspective, herein, we report an eco-friendly and inexpensive route for the synthesis of 4(3H)-quinazolinones using magnetically separable core-shell-like bimetallic Fe₃O₄-MAA@Co-MOF@Cu-MOF NPs as environmentally-friendly heterogeneous catalysts. To the best of our knowledge, this is the first example of the integration of two different types of MOFs, which contain two different metal ions (Co²⁺ in the core and Cu²⁺ in the shell) using an external ligand. Our study not only introduces a novel nanostructured catalyst for the organic reaction but also presents a new strategy for the combination of two MOFs in one particle at the nanometer level. To survey the structural and compositional features of the synthesized nanocatalyst, a variety of spectroscopic and microscopic techniques including FT-IR, XRD, BET, TEM, HR-TEM, FE-SEM, EDX, EDX-mapping, TGA, VSM, and ICP-OES were employed. The combination of magnetic Co-MOF with Cu-MOF leads to achieving unique structural and compositional properties for Fe₃O₄-MAA@Co-MOF@Cu-MOF NPs with a particle size of 20-70 nm, mesostructure, and relatively large specific surface area (236.16 m² g^-1). The as-prepared nanostructured catalyst can be an excellent environment catalyst for the synthesis of a wide library of 4(3H)-quinazolinones derivatives, including electron-donating and electron-withdrawing aromatic, heteroaromatic, and aliphatic compounds under solvent-free conditions much better than the parent precursors. Moreover, by investigating the longevity of the nanocatalyst, the conclusion could be derived that the aforesaid nanocatalyst is stable under reaction conditions and could be recycled for at least seven recycle runs without a discernible decrease in its catalytic activity.

Excited state processes of dinuclear Pt(II) complexes bridged by 8-hydroxyquinoline

Dinuclear d⁸ Pt(II) complexes, where two mononuclear square planar Pt(II) units are bridged in an "A-frame" geometry, possess photophysical properties characterised by either metal-to-ligand-(MLCT) or metal-metal-ligand-to-ligand charge transfer (MMLCT) transitions determined by the distance between the two Pt(II) centres. When using 8-hydroxyquinoline (8HQH) as the bridging ligand to construct novel dinuclear complexes with general formula [C^NPt(μ-8HQ)]₂, where C^N is either 2-phenylpyridine (1) or 7,8-benzoquinoline (2), triplet ligand-centered (³LC) photophysics results echoing that in a mononuclear model chromophore, [Pt(8HQ)₂] (3). The lengthened Pt-Pt distances of 3.255 Å (1) and 3.243 Å (2) results in a lowest energy absorption centred around 480 nm assigned as having mixed LC/MLCT character by TD-DFT, mirroring the visible absorption spectrum of 3. Additionally, 1 and 2 exhibit ³LC photoluminescence with limited quantum yields (0.008) from broad transitions centred near 680 nm. Photoexcitation of 1-3 leads to an initially prepared excited state that relaxes within 15 ps to a ³LC excited state centred on the 8HQ bridge, which then persists for several microseconds. All the experimental results correspond well with DFT electronic structure calculations.

Citric acid tuned negative thermal quenching of all inorganic copper-based perovskites

Copper-based perovskites, with lower electronic dimensions and high photoluminescence quantum yields (PLQY), which are non-toxic and thermally stable, have been reported since 2019 and have immediately attracted great attention. So far, only a few studies have researched the temperature-dependent photoluminescence properties, posing a challenge in ensuring the stability of the material. In this paper, the temperature-dependent photoluminescence properties have been investigated in detail, and a negative thermal quenching of all-inorganic CsCu₂I₃ perovskites has been studied. Moreover, the negative thermal quenching property can be tuned with the assistance of citric acid, which has not been reported before. The Huang-Rhys factors are calculated to be 46.32/38.31, which is higher than for many semiconductors and perovskites.

A Pyridyl-1,2-azaborine Ligand for Phosphorescent Neutral Iridium(III) Complexes

A novel 1,2-azaborine (i.e., 4-methyl-2-(pyridin-2-yl)-2,1-borazaronaphthalene, 1a) has been synthesized and used for the first time as a B-N alternative to common cyclometalating ligands to obtain neutral phosphorescent iridium(III) complexes (i.e., 2a, 3, and 4) of general formula [Ir(C^∧N)₂(N^∧NB)], where C^∧N indicates three different cyclometalating ligands (Hppy = 2-phenylpyridine; Hdfppy = 2-(2,4-difluoro-phenyl)pyridine; Hpqu = 2-methyl-3-phenylquinoxaline). Moreover, the azaborine-based complex 2a was compared to the isoelectronic C═C iridium(III) complex 2b, obtained using the corresponding 2-(naphthalen-2-yl)pyridine ligand 1b. Due to the dual cyclometalation mode of such C═C ligand, the isomeric complex 2c was also obtained. All new compounds have been fully characterized by NMR spectroscopy and high-resolution mass spectrometry (MS), and the X-ray structure of 2a was determined. The electronic properties of both ligands and complexes were investigated by electrochemical, density functional theory (DFT), and photophysical methods showing that, compared to the naphthalene analogues, the azaborine ligand induces a larger band gap in the corresponding complexes, resulting in increased redox gap (basically because of the highest occupied molecular orbital (HOMO) stabilization) and blue-shifted emission bands (e.g., λ_max = 523 vs 577 nm for 2a vs 2b, in acetonitrile solution at 298 K). On the other hand, the ³LC nature of the emitting state is the same in all complexes and remains centered on the pyridyl-borazaronaphthalene or its C═C pyridyl-naphthalene analogue. As a consequence, the quantum yields of such azaborine-based complexes are comparable to those of the more classical C═C counterparts (e.g., photoluminescence quantum yield (PLQY) = 16 vs 22% for 2a vs 2b, in acetonitrile solution at 298 K) but with enhanced excited-state energy. This proves that such type of azaborine ligands can be effectively used for the development of novel classes of photoactive transition-metal complexes for light-emitting devices or photocatalytic applications.

Lanthanide Hexacyanidoruthenate Frameworks for Multicolor to White-Light Emission Realized by the Combination of d-d, d-f, and f-f Electronic Transitions

We report an effective strategy toward tunable room-temperature multicolor to white-light emission realized by mixing three different lanthanide ions (Sm³⁺, Tb³⁺, and Ce³⁺) in three-dimensional (3D) coordination frameworks based on hexacyanidoruthenate(II) metalloligands. Mono-lanthanide compounds, K{Ln^III(H₂O)_n[Ru^II(CN)₆]}·mH₂O (1, Ln = La, n = 3, m = 1.2; 2, Ln = Ce, n = 3, m = 1.3; 3, Ln = Sm, n = 2, m = 2.4; 4, Ln = Tb, n = 2, m = 2.4) are 3D cyanido-bridged networks based on the Ln-NC-Ru linkages, with cavities occupied by K⁺ ions and water molecules. They crystallize differently for larger (1, 2) and smaller (3, 4) lanthanides, in the hexagonal P6₃/m or the orthorhombic Cmcm space groups, respectively. All exhibit luminescence under the UV excitation, including weak blue emission in 1 due to the d-d ³T_1g → ¹A_1g electronic transition of Ru^II, as well as much stronger blue emission in 2 related to the d-f ²D_3/2 → ²F_5/2,7/2 transitions of Ce^III, red emission in 3 due to the f-f ⁴G_5/2 → ⁶H_{5/2,7/2,9/2,11/2} transitions of Sm^III, and green emission in 4 related to the f-f ⁵D₄ → ⁷F_6,5,4,3 transitions of Tb^III. The lanthanide emissions, especially those of Sm^III, take advantage of the Ru^II-to-Ln^III energy transfer. The Ce^III and Tb^III emissions are also supported by the excitation of the d-f electronic states. Exploring emission features of the Ln^III-Ru^II networks, two series of heterobi-lanthanide systems, K{Sm_xCe_1-x(H₂O)_n[Ru(CN)₆]}·mH₂O (x = 0.47, 0.88, 0.88, 0.99, 0.998; 5-9) and K{Tb_xCe_1-x(H₂O)_n[Ru(CN)₆]}·mH₂O (x = 0.56, 0.65, 0.93, 0.99, 0.997; 10-14) were prepared. They exhibit the composition- and excitation-dependent tuning of emission from blue to red and blue to green, respectively. Finally, the heterotri-lanthanide system of the K{Sm_0.4Tb_0.599Ce_0.001(H₂O)₂[Ru(CN)₆]}·2.5H₂O (15) composition shows the rich emission spectrum consisting of the peaks related to Ce^III, Tb^III, and Sm^III centers, which gives the emission color tuning from blue to orange and white-light emission of the CIE 1931 xy parameters of 0.325, 0.333.

The effect of substituents and molecular aggregation on the room temperature phosphorescence of a twisted π-system

Room temperature phosphorescence of an intrinsically apolar twisted π-system is modulated by polar substituents. Persistent phosphorescence is visible by eye in poder, induced by molecular aggregation.