Photoluminescence Properties of Multinuclear Copper(I) Compounds

Luminescence Thermochromism of a Noncluster Copper Iodide Complex

Hybrid copper(I) halide materials are currently attracting significant attention due to their exceptional luminescence properties, offering great potential for the development of multifunctional emissive materials with, in addition, eco-friendly features. A binuclear copper iodide complex, based on the [Cu2I2L4] motif with phosphite derivatives as ligands, has been synthesized and structurally characterized. Photophysical investigations indicate that this complex displays luminescence thermochromic properties, which are characterized by a temperature-dependent change in the relative intensity of two emission bands. The high-contrast luminescence thermochromism, with an important color variation from purple to cyan, is ascribed to the thermal equilibrium of two different excited states. While thermochromism is relatively known for multimetallic complexes, the perfectly controlled thermochromism of the studied compound is unprecedented for a binuclear complex. From theoretical investigations, this original feature is due to the coordination of phosphite ligands, which induces a specific energy layout of the complex, presenting vacant orbitals of varying nature. This single-component, dual-emissive binuclear complex, displaying relevant sensitivity temperature response, presents great potential for luminescence ratiometric thermometry applications. This study underlines the relevance of the ligand engineering strategy in developing original, emissive, and sustainable copper-based materials.

Coinage metal(I) clusters supported by a 1,10-phenanthroline-phosphine: orange-to-NIR phosphorescence, metallophilic interactions and enhanced cytotoxicity

A series of small coinage metal(I) clusters has been selectively synthesized using 2-(diphenylphosphino)-1,10-phenanthroline (L), a new promising dimetal-binding P,N,N'-ligand (L). Its reaction with CuI yields the complex [Cu2L2(μ2-I)]2[Cu2I4], while the treatment of L with Au(tht)Cl/Ag+ or Au(tht)Cl/Cu+ systems leads to the assembly of [Au2AgL2Cl2]+, [Au2CuL2Cl2]+, [CuAuL2]2+ and [AgAuL2]2+ clusters. Theoretical analysis revealed pronounced intermetallic close shell interactions in these di- and trinuclear ensembles. At 298 K, the title compounds exhibit an orange and near-infrared (NIR) phosphorescence with lifetimes of 0.344-38 μs and quantum efficiencies of 1-21%. Theoretical considerations suggest a 3(M+L)LCT type for the observed phosphorescence. In addition, the above clusters exhibit a strong dose-dependent cytotoxic effect on A549, HepG2, Hep2 and MRC5 human cells with IC50 values ranging from 1.26 to 11.1 μM.

Rigidochromism of tetranuclear Cu(I)-pyrazolate macrocycles: steric crowding with trifluoromethyl groups

Macrocyclic Cu(I)-pyrazolate tetramers (Cu4pz4) can fold into compact structures with luminescent Cu4 cores whose emission wavelengths are sensitive to steric effects along the periphery of the macrocycle. Introducing CF3 at the C4 position of 3,5-di-tBu-pyrazolate increases steric crowding that modifies the conformational behavior of the Cu4pz4 complex, highlighted by a low-temperature martensitic transition. Variable-temperature analysis of solid-state luminescence reveal an unexpected blueshifting of emission with rising temperature.

Realizing Color Transitions for Three Copper (I) Cluster Organic-Inorganic Hybrid Materials by Adjusting Reaction Conditions

Copper iodide organic-inorganic hybrid materials have been favored by many researchers in the field of solid-state lighting (SSL) due to their structural diversity and optical adjustability. In this paper, three isomeric copper iodide cluster hybrid materials, Cu4I6(L)2(1), Cu5I4.5Cl2.5(L)2(2) and Cu5I7(L)2) (3) (L=1-(4-methylpyrimidin-2-yl)-1,4-diazabicyclo[2.2.2]octan-1-ium), were achieved by adjusting the reaction conditions. The crystal color transit from green, yellow to orange and the internal quantum yield (IQY) increase from 57 %-88 %. All three complexes have good thermal stability, good solution processability, and high quantum yield. And origin and mechanism of luminescence of complexes were further studied. This study can provide ideas and theoretical basis for the regulation of cuprous iodide cluster luminescent materials.

Organic-Inorganic Hybrid Halide X-ray Scintillator with High Antiwater Stability

In recent years, low-dimensional organic-inorganic hybrid metal halides have garnered significant attention for optoelectronic applications due to their exceptional photophysical properties, despite their persistent challenge of low stability. Addressing this challenge, our study introduces 1-[5-(trifluoromethyl)pyridin-2-yl]piperazinium (TFPP) as a cation, harvesting a novel one-dimensional hybrid cadmium-based halide semiconductor (TFPP)CdCl4, which exhibits intense blue-light emission upon UV excitation. Additionally, (TFPP)CdCl4 demonstrates a high scintillation performance under X-ray excitation, producing 16600 ± 500 photons MeV-1 and achieving a low detection limit of 0.891 μGyair s-1. Notably, (TFPP)CdCl4 showcases remarkable stability against water, intense light sources, heating, and corrosive environments, positioning it as a promising candidate for optoelectronic applications. Through a blend of experimental techniques and theoretical analyses, including density functional theory calculations, we elucidate the unique photophysical properties and structural stability of (TFPP)CdCl4. These findings significantly contribute to the understanding of low-dimensional hybrid halide semiconductors, offering valuable insights into their potential application in advanced optoelectronic devices and paving the way for further research in this field.

Multicolor photoluminescence of Cu14 clusters modulated using surface ligands

Copper nanoclusters exhibit unique structural features and their molecular assembly results in diverse photoluminescence properties. In this study, we present ligand-dependent multicolor luminescence observed in a Cu14 cluster, primarily protected by ortho-carborane-9,12-dithiol (o-CBDT), featuring an octahedral Cu6 inner kernel enveloped by eight isolated copper atoms. The outer layer of the metal kernel consists of six bidentate o-CBDT ligands, in which carborane backbones are connected through μ3-sulphide linkages. The initially prepared Cu14 cluster, solely protected by six o-CBDT ligands, did not crystallize in its native form. However, in the presence of N,N-dimethylformamide (DMF), the cluster crystallized along with six DMF molecules. Single-crystal X-ray diffraction (SCXRD) revealed that the DMF molecules were directly coordinated to six of the eight capping Cu atoms, while oxygen atoms were bound to the two remaining Cu apices in antipodal positions. Efficient tailoring of the cluster surface with DMF shifted its luminescence from yellow to bright red. Luminescence decay profiles showed fluorescence emission for these clusters, originating from the singlet states. Additionally, we synthesized microcrystalline fibers with a one-dimensional assembly of DMF-appended Cu14 clusters and bidentate DPPE linkers. These fibers exhibited bright greenish-yellow phosphorescence emission, originating from the triplet state, indicating the drastic surface tailoring effect of secondary ligands. Theoretical calculations provided insights into the electronic energy levels and associated electronic transitions for these clusters. This work demonstrated dynamic tuning of the emissive excited states of copper nanoclusters through the efficient engineering of ligands.

Organo Chalcogenone-Triggered Luminescent Copper(I) Clusters for Light Emitting Applications

A novel organo sulfur and selenium-controlled emission behavior in discrete copper(I) clusters has been demonstrated for the first time. The pentanuclear [Cu5Br5(L1)2] (1), trinuclear [Cu3Br3(L2)2] (2), dinuclear [Cu2I2(L1)2] (3), and tetranuclear [Cu4I4(L2)2CH3CN] (4) copper(I) discrete clusters have been synthesized from the reaction between L1 [L1 = 1-isopropyl-3-(pyridin-2-yl)-imidazol-2-thione] or L2 [L2 = 1-isopropyl-3-(pyridin-2-yl)-imidazol-2-selone] chelating ligands and corresponding copper(I) halide salts. These new clusters have been characterized by FT-IR, UV-visible, thermogravimetric analysis, and fluorescence spectroscopy techniques. Single-crystal X-ray diffraction studies reveal that 1-4 consists of abundant d10-d10 interactions. The structural and bonding features of clusters have been investigated using density functional theory calculations. Notably, the L2-ligated 2 and 4 are poorly emissive, while L1-ligated 1 and 3 showed strong emission in the orange and green regions, respectively. The time-dependent density functional theory natural transition orbital calculations of 1 and 3 reveal the nature of the transitions contributed by 3MLCT/3LLCT/3ILCT. Photoluminescence quantum yields of 1 and 3 are 19 and 11%, with average lifetimes of 21.55 and 6.57 μs, respectively. 1 and 3 were coated on prototype LED bulbs for light-emitting performance.

Twisted and Disconnected Chains: Flexible Linear Tetracuprous Arrays and a Decanuclear CuI Cluster as Blue- and Green/Yellow-Light Emitters

Defined arrays of transition metal ions embedded in tailored polydentate ligand scaffolds allow for a systematic design of their physical properties. Such molecular strings of closed-shell transition metal centers are particularly interesting for Group 11 metal ions in the oxidation state +1 if they undergo metallophilic d10···d10 contact interactions since these clusters are oftentimes efficient photoluminescence (PL) emitters. Copper is particularly attractive as a sustainable earth-abundant coinage metal source and because of the ability of several CuI complexes to serve as powerful thermally activated delayed fluorescence (TADF) emitters in molecular/organic light-emitting devices (OLEDs). Our combined synthetic, crystallographic, photophysical, and computational study describes a straight tetracuprous array possessing a centrally disconnected CuI2···CuI2 chain and a continuous helically bent CuI4 complex. This molecular helix undergoes a facile rearrangement in diethyl ether solution, yielding an unprecedented nanosized CuI10 cluster (2.9 × 2.0 nm) upon crystallization. All three clusters show either bright blue phosphorescence, TADF, or green/yellow multiband phosphorescence with quantum yields between 6.5 and 67%, which is persistent under hydrostatic pressure up to 30 kbar. Temperature-dependent PL investigations in combination with time-dependent density-functional theory (TD-DFT) calculations and void space analyses of the crystal packings complement a comprehensive correlation between the molecular structures and photoluminescence properties.

Assembly of Copper Alkynyl Clusters into Dimensionally Diverse Coordinated Polymers Mediated by Pyridine Ligands

Surface ligands play crucial roles in modifying the properties of metal nanoclusters and stabilizing atomically precise structures, and also serve as vital linkers for constructing cluster-based coordination polymers. In this study, we present the results of the solvothermal synthesis of eight novel copper alkynyl clusters incorporating pyridine ligands using a one-pot method. The resulting compounds underwent characterization through elemental analysis, Fourier transform infrared (FT-IR) spectroscopy, powder X-ray diffraction (PXRD), and single-crystal X-ray diffraction (SCXRD). Our observations revealed that distinct pyridine ligands with varying lengths and coordination sites exert significant influence on the structure and dimensionality of the clusters. The structural diversity of these clusters led to the formation of one-dimensional (1D), two-dimensional (2D), or dimer arrangements linked by seven pyridine bridging ligands. Remarkably, these complexes exhibited unique UV-vis absorption and photoluminescence properties, which were influenced by the specific bridging ligand and structural framework. Furthermore, density functional theory (DFT) calculations demonstrated the capability of the conjugated system in the pyridine ligand to impact the band gap of clusters. This study not only unveils the inherent structural diversity in coordination polymers based on copper alkynyl clusters but also offers valuable insights into harnessing ligand engineering for structural and property modulation.

Ultrastable Copper Iodide Hybrid with Intrinsic Greenish White-Light Emission by Incorporating an Anionic Inorganic Functional Unit into an Extended Structure

Incorporating a functional unit into the multidimensional coordination polymer skeleton is an efficient way to improve the stability of materials and expand their application. In this paper, anionic copper iodide inorganic functional modules are incorporated into one-dimensional extended chains by using a unique bidentate cationic organic ligand. Benefiting from the ionic extended structure, the resulting hybrid possesses a remarkable stability with a decomposition temperature as high as 300 °C. Meanwhile, the hybrid material exhibits intrinsic greenish white-light emission with a high photoluminescent quantum yield of 70%. The emission was investigated by temperature-dependent emission spectra, which proved to be the result of the synergistic effect of two energy states. The novel synthetic strategy provides an efficient route for the development of functional organic metal halides.

Suppressing the Thermal Quenching Effect via a Cluster Conformer in Copper(I)-Iodide Coordination Polymeric Phosphors for High-Power White LED Lighting

High-power LED lighting is a crucial challenge due to the notorious thermal quenching (TQ) effect of traditional phosphors at high operating currents, which would result in poor device performance and hamper practical optoelectronic application. Herein, we demonstrate ligand engineering of a cubane- versus staircase-like [Cu4I4] conformer as a node in coordination polymers, which remarkably suppresses the TQ effect of cluster-based photoluminescence. For complex 1 (the formula [Cu4I4(bbimb)2]n) with the cubane-like [Cu4I4] conformer as a node, the metallophilicity interaction enables ultrabright triplet emission with a photoluminescence quantum yield over 82%, and the phonon-assisted detrapping process of excitons effectively suppresses the TQ effect in the wide temperature range. In contrast, the staircase-like [Cu4I4] conformer as a node in complex 2 (the formula [Cu4I4(bbtmb)2]n) exhibits a serious TQ effect over the investigated temperature. Phosphor-converted white LEDs (pc-wLEDs) were fabricated by integrating the cluster-based coordination polymers as a color converter, and their electroluminescence performances were investigated under high bias currents. The prototype pc-wLED device by incorporating the phosphor with the suppressed TQ effect exhibits a continuous rise in brightness under a high bias current of 300 mA. The results demonstrate that ligand engineering of the cluster conformer via suppressing the TQ effect proves efficient in designing an ideal color converter for high-power pc-wLED lighting.

Synthesis and Photophysical Properties of Silver(I) Coordination Polymers Bridged by Dimethylpyrazine: Comparison of Emissive Excited States between Silver(I) and Copper(I) Congeners

Highly luminescent silver(I) coordination polymers [Ag2X2(PPh3)2(Me2pyz)]n (X = I, Br, Cl; Me2pyz: 2,5-dimethylpyrazine) were prepared together with copper congeners [Cu2X2(PPh3)2(Me2pyz)]n (X = I, Br). All the complexes showed thermally activated delayed fluorescence from the charge-transfer states in the visible region, from blue to red. The isomorphous relationship among the complexes allowed a detailed discussion of the effect of halogenido ligands and crystal packing on their luminescence energy. The relaxation in the emissive excited states (ESs) was determined to be more remarkable in silver complexes than in copper complexes despite their isomorphous structures, and the electronic effect of halogenido ligands was comparable to the effect of relaxation in emissive ESs.

Dual-Emissive γ-[Cu4I8]4- Enables Luminescent Thermochromism in an Organic-Inorganic Hybrid Copper(I) Halide

A highly luminescent (C13H28N2)2Cu4I8 single crystal containing isolated γ-[Cu4I8]4- anionic cluster was synthesized without the use of unsaturated cations. To the best of our knowledge, compounds bearing such like anions are not dual-emitting under UV excitation. However, dual emission does occur in (C13H28N2)2Cu4I8. Moreover, the emission bands were found to be temperature-sensitive, allowing tuning of the emission colors from blue (0.19, 0.20) to green (0.33, 0.47) in the Commission International de L' Eclairage (CIE) chromaticity coordinates. Remarkably, the color could be restored on returning to the initial temperature, confirming an efficient and reversible luminescent thermochromic effect in (C13H28N2)2Cu4I8. The origin of this excellent optical performance is discussed, and the difference in the mechanism with the dual-emissive Cu(I) halide complexes is also elucidated. Overall, our work provides a promising way to achieve efficient luminescent thermochromism. The developed (C13H28N2)2Cu4I8 represents one of the viable alternatives for eco-friendly luminescent thermochromic materials.

Pargyline-phosphine copper(I) clusters with tunable emission for light-emitting devices

Three pargyline-phosphine copper(I) clusters, [Cu4(CC-C9H12N)3(PPh3)4](PF6) (1) and [Cu6(CC-C9H12N)4(dppy)4](X)2 (dppy = diphenyl-2-pyridylphosphine; X = PF6 for 2 and X = ClO4 for 3), were synthesized. Their structures were fully characterized using various spectroscopic methods and X-ray crystallography, which showed that the stoichiometry and nature of pargyline and phosphine ligands play an important role in tuning the structure and photophysical features of Cu(I) clusters. Interestingly, clusters 1, 2 and 3 exhibited red, orange and yellow phosphorescence with high quantum yields of 88.5%, 22.0% and 40.2%, respectively, at room temperature. Moreover, clusters 1-3 show distinct temperature-dependent emissions. The excellent luminescence performance of 1 and 3 was designed and employed for the construction of monochrome and white light-emitting devices (LEDs).

Organic-Inorganic Hybrid Glasses of Atomically Precise Nanoclusters

Organic-inorganic atomically precise nanoclusters provide indispensable building blocks for establishing structure-property links in hybrid condensed matter. However, robust glasses of ligand-protected nanocluster solids have yet to be demonstrated. Herein, we show [Cu4I4(PR3)4] cubane nanoclusters coordinated by phosphine ligands (PR3) form robust melt-quenched glasses in air with reversible crystal-liquid-glass transitions. Protective phosphine ligands critically influence the glass formation mechanism, modulating the glasses' physical properties. A hybrid glass utilizing ethyldiphenylphosphine-based nanoclusters, [Cu4I4(PPh2Et)4], exhibits superb optical properties, including >90% transmission in both visible and near-infrared wavelengths, negligible self-absorption, near-unity quantum yield, and high light yield. Experimental and theoretical analyses demonstrate the structural integrity of the [Cu4I4(PPh2Et)4] nanocluster, i.e., iodine-bridged tetranuclear cubane, has been fully preserved in the glass state. The strong internanocluster CH-π interactions found in the [Cu4I4(PPh2Et)4] glass and subsequently reduced structural vibration account for its enhanced luminescence properties. Moreover, this highly transparent glass enables performant X-ray imaging and low-loss waveguiding in fibers drawn above the glass transition. The discovery of "nanocluster glass" opens avenues for unraveling glass formation mechanisms and designing novel luminescent glasses of well-defined building blocks for advanced photonics.

Electroluminescent Clusters

Optoelectronic cluster materials emerge rapidly in recent years especially for light-emitting devices, owing to their 100 % exciton harvesting and unique organic-inorganic hybrid structures with tunable excited-state characteristics for thermally activated delayed fluorescence and/or phosphorescence and inheritable photo- and thermo-stability. However, for efficient electroluminescence, excited-state compositions of cluster emitters should be tuned through ligand engineering to enhance ligand-centered radiative components and reduce cluster-centered quenching states. Nonetheless, the balance of optoelectronic properties requires delicate and controllable ligand functionalization. On the other hand, in addition to balancing carrier fluxes, it showed that device engineering, especially host matrixes and interfacial optimization, can not only alleviate triplet quenching, but also modify processing and passivate defects. As consequence, the record external quantum efficiencies of cluster light-emitting diodes already reached ≈30 %. Herein, we overview recent progress of electroluminescent cluster materials and discuss their structure-property relationships, which would inspire the continuous efforts making cluster light-emitting diodes competent as the new generation of displays and lighting sources.

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.

Allochroic cluster light-emitting diodes based on unique μ3-tetraphosphine Cu3X3 crowns with tunable excited states

Multicomponent excited states endow copper iodide clusters with allochroic properties under diverse stimuli. However, crystal states are required, and cluster stimulus sensitivity hampers electroluminochromism. We developed PhQPCu3X3 (X = Cl, Br, and I) with the first μ3-bridging tetraphosphine ligand, whose Cu3X3 crowns were exposed to external stimulus. The increased proportion of Cu3X3 results in equal contributions of cluster- and ligand-centered components to excited states, the former of which is highly sensitive to grind, vapor, and, especially, electric stimuli, due to semi-exposed Cu3X3. Through vacuum evaporation and vapor fumigation of cluster-based emissive layers, the diodes' electroluminescence colors changed from yellow to white. Joule heat during device operation induced further color variation to orange, corresponding to Commission Internationale de l'Eclairage coordinates of PhQPCu3I3 changed from (0.44 ± 0.1, 0.34 ± 0.1) to (0.57 ± 0.1, 0.42 ± 0.1). These results demonstrate the superiority of luminescent clusters in accurate excited-state modulation, holding promise for wide applications.

Photoluminescent copper(I) iodide alkylpyridine thin films as sensors for volatile halogenated compounds

The paper presents the fabrication and characterization of [CuI(L)]n thin films, where L represents various alkylpyridine ligands including 4-methylpyridine, 3-methylpyridine, 2-methylpyridine, 4-tbutylpyridine, 3,4-dimethylpyridine, and 3,5-dimethylpyridine. The thin films were synthesized by exposing the corresponding ligands to CuI thin films through vapor deposition. The coordination reactions occurring on the films were investigated using PXRD and time-dependent photoluminescence spectroscopy, and a comparison was made between the structures of the thin films and the corresponding powder phases. The films showed primarly blue emission (λem = 457-515 nm) and polymeric structures with excited state lifetimes ranging from 0.6 to 5.5 μs. Significantly, the studied compounds exhibited fast reversible luminescence quenching when exposed to vapors of dichloromethane and dibromomethane (15 and 30 min respectively), and the luminescence was restored upon re-exposure to the alkylpyridine ligand (after 20 min). These findings indicate that these thin films hold promise for applications as sensors (with sensitive and reversible detection capability) for volatile halogen-based compounds (VHC).

Time-resolved radioluminescence of the Cu(I) cluster Cu4I62-. Different responses to photo, X-ray, β-ray and α-particle excitation

Time-resolved radioluminescence (TRRL) properties of the Cu(I) cluster Cu4I62- upon pulsed X-ray, β-ray or α-particle excitation are described. The longer (>2 μs) TRRL component displays exponential decay comparable to pulsed UV excitation; however, temporal behaviour at shorter times indicates that high local excited state density provides an alternative decay channel.

High-Efficiency Pure Blue Circularly Polarized Phosphorescence from Chiral N-Heterocyclic-Carbene-Stabilized Copper(I) Clusters

Circularly polarized luminescence (CPL) materials have attracted considerable attention for their promising applications in encryption, chiral sensing, and three-dimensional (3D) displays. However, the preparation of high-efficiency, pure blue CPL materials remains challenging. In this study, we reported an enantiomeric pair of triangle copper(I) clusters (R/S-Cu3) rigidified by employing chiral N-heterocyclic carbene (NHC) ligands with two pyridine-functionalized wingtips. These chiral clusters emitted pure blue phosphorescence that overlapped with that of the commercial blue phosphor having Commission Internationale de l'Eclairage (CIE) chromaticity coordinates of (0.14, 0.10), and the films exhibited an unprecedented photoluminescence quantum yield (PLQY) of ∼70.0%. Additionally, the solutions showed very bright circularly polarized phosphorescence (CPP) with a dissymmetry factor of ±2.1 × 10-3. The excellent solubility and photostability endowed these pure-blue-emitting chiral clusters with promising applications as pure blue CPP inks for 3D printing white objects, such as precise-atomic-enlarged models of metal clusters and a lovely white stereoscopic "rabbit". The intricate mechanism underlying blue phosphorescence in this small cluster and across various states is elucidated through a comprehensive approach that integrates thorough analysis of luminescence properties, controlled experiments, and theoretical calculations. For the first time, we propose that the dominant high-energy emission center is constituted by delocalized hybrid orbitals over multiple atomic centers, encompassing both the metal and the coordinated atoms. This challenges stereotypical assumptions that the cluster center solely supports low-energy emissions. This work expands the currently limited range of CPP functional materials and provides a new direction for CPP applications involving NHC-stabilized metal clusters.

Cluster-Centered Excited-State-Induced Bright Low-Energy Emissive Hybrid Copper Iodide Constructing Stable White LEDs

Herein, we successfully synthesized a stable copper iodide hybrid with a 0D structure, (C20H20P)2Cu2I4, in which [Cu2I4]2- dimers with a short Cu-Cu distance (2.64 Å) are isolated and surrounded by [C20H20P]+ organic cations. Bright broadband yellow emission (576 nm) featuring a wide excitation range from 240 to 450 nm was achieved, along with a large Stokes shift (211 nm), long-lived lifetime (1.99 μs), and zero self-absorption. The results combined with crystal structure, spectroscopy analysis, and theoretical studies reveal that a cluster-centered excited state is responsible for this yellow emission. Importantly, the structure of (C20H20P)2Cu2I4 remains unchanged even after soaking in water for 30 days or heating at 80 °C for 240 h due to the intermolecular interaction. Furthermore, a stable white LED showing a naturally correlated color temperature (CCT) of 6573 K and CIE color coordinate of (0.31, 0.37) was also demonstrated. This work demonstrates efficient light emitters based on lead-free and stable metal halides for lighting, providing an important reference for the development of stable, high-performance metal halide phosphors.

Cu(I)-thioether coordination complexes based on a chiral cyclic β-amino acid ligand

Coordination complexes, particularly metalloproteins, highlight the significance of metal-sulfur bonds in biological processes. Their unique attributes inspire efforts to synthetically reproduce these intricate metal-sulfur motifs. Here, we investigate the synthesis and characterization of copper(I)-thioether coordination complexes derived from copper(I) halides and the chiral cyclic β-amino acid trans-4-aminotetrahydrothiophene-3-carboxylic acid (ATTC), which present distinctive structural properties and ligand-to-metal ratios. By incorporating ATTC as the ligand, we generated complexes that feature a unique chiral conformation and the capacity for hydrogen bonding, facilitating the formation of distinct geometric structures. Through spectroscopic analyses and density functional theory (DFT) calculations, we studied the complexes' optical properties, including their emission bands and variable second-harmonic generation (SHG) efficiencies, which vary based on the halide used. Our findings underscore the potential of the ATTC ligand in creating unusual coordination complexes and pave the way for further investigations into their potential applications, particularly within materials science.

Cubane Dimerization: Cu4 vs Cu8 Copper Iodide Clusters

Copper(I) halides are well-known for their structural diversity and rich photoluminescence properties, showing great potential for the development of solid-state lighting technology. A series of four molecular copper iodide clusters based on the [Cu4I4] cubane geometry is reported. Among them, [Cu8I8] octanuclear clusters of rare geometry resulting from dimerization of the tetranuclear counterparts were also synthesized. Two different phosphine ligands were studied, bearing either a styrene or an ethyl group. Therefore, the effect of the dimerization and of the ligand nature on the photophysical properties of the resulting clusters is investigated. The structural differences were analyzed by single-crystal X-ray diffraction (SCXRD), solid-state nuclear magnetic resonance (NMR), infrared, and Raman analyses. Compared to the ethyl group, the styrene function appears to greatly impact the photophysical properties of the clusters. The luminescence thermochromic properties of the ethyl derivatives and the intriguing photophysical properties of the clusters with styrene function were rationalized by density functional theory (DFT) calculations. Thus, the styrene group significantly lowers in energy the vacant orbitals and consequently affects the global energetic layout of the clusters. From this study, it was found that the nuclearity of copper iodide clusters eventually has less influence on the photophysical properties than the nature of the ligand. The design of proper ligands should therefore be considered when developing materials for specific lighting applications.

Mononuclear copper(I) complexes bearing a 3-phenyl-5-(pyridin-4-yl)-1,2,4-triazole ligand: synthesis, crystal structure, TADF-luminescence, and mechanochromic effects

Three new mononuclear heteroleptic copper(I) halide complexes, [CuL(PPh3)2X] (X = Cl, Br, I), based on 3-phenyl-5-(pyridin-4-yl)-1,2,4-triazole (L) and triphenylphosphine (PPh3) ligands, have been prepared by reaction of CuX (X = Cl, Br, I), L and PPh3 in a molar ratio of 1 : 1 : 2 in MeCN solutions. The synthesized complexes exhibit blue light emission in solutions and bright green emission in the crystal state with quantum yields of up to 100%. The luminescence decay analysis and density functional theory calculations revealed that the emission of solid samples at room temperature corresponds to the thermally activated delayed fluorescence, while that at 77 K is assigned to phosphorescence. Utilizing the studied complexes in OLED heterostructures resulted in high-performing green-emitting devices with an external quantum efficiency of up to 13.4%.

Polymeric copper(I)-NHC complexes with bulky bidentate (N^C) ligands: synthesis and solid-state luminescence

Starting from imidazolium chlorides bearing bulky nitrogen donors, a series of four complexes, mainly [Cu(C^N)Cl]n coordination polymers were obtained directly as luminescent species by simple filtration from the aqueous reaction medium, highlighting a simple, eco-friendly, robust and reproducible synthetic procedure. Additionally, we have shown on the most efficient example that chloride could be exchanged very easily by other halides/pseudohalides (Br-, I-, NCS-, N3-) allowing to slightly modulate the emitted colour while conserving the polymeric structure, except for azide for which a dimer was obtained. The combination of chemical analyses, of photoluminescence studies in the solid state including quantum yield measurement and X-ray diffraction on single crystals and as-synthesized microcrystalline powders highlighted that the polymeric luminescent species was indeed obtained directly by simple filtration and that no major alteration of the structure was observed upon recrystallisation. Samples of all polymeric complexes displayed remarkable stability towards air oxidation remaining unchanged upon storage for several months and partially retaining their photoluminescence properties even after a thermal treatment at 100 °C for 24 h.

Binuclear Copper(I) Complexes for Near-Infrared Light-Emitting Electrochemical Cells

Two binuclear heteroleptic CuI complexes, namely Cu-NIR1 and Cu-NIR2, bearing rigid chelating diphosphines and π-conjugated 2,5-di(pyridin-2-yl)thiazolo[5,4-d]thiazole as the bis-bidentate ligand are presented. The proposed dinuclearization strategy yields a large bathochromic shift of the emission when compared to the mononuclear counterparts (M1-M2) and enables shifting luminescence into the near-infrared (NIR) region in both solution and solid state, showing emission maximum at ca. 750 and 712 nm, respectively. The radiative process is assigned to an excited state with triplet metal-to-ligand charge transfer (3 MLCT) character as demonstrated by in-depth photophysical and computational investigation. Noteworthy, X-ray analysis of the binuclear complexes unravels two interligand π-π-stacking interactions yielding a doubly locked structure that disfavours flattening of the tetrahedral coordination around the CuI centre in the excited state and maintain enhanced NIR luminescence. No such interaction is present in M1-M2. These findings prompt the successful use of Cu-NIR1 and Cu-NIR2 in NIR light-emitting electrochemical cells (LECs), which display electroluminescence maximum up to 756 nm and peak external quantum efficiency (EQE) of 0.43 %. Their suitability for the fabrication of white-emitting LECs is also demonstrated. To the best of our knowledge, these are the first examples of NIR electroluminescent devices based on earth-abundant CuI emitters.

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.

Carbene-stabilized enantiopure heterometallic clusters featuring EQE of 20.8% in circularly-polarized OLED

Bright and efficient chiral coinage metal clusters show promise for use in emerging circularly polarized light-emitting materials and diodes. To date, highly efficient circularly polarized organic light-emitting diodes (CP-OLEDs) with enantiopure metal clusters have not been reported. Herein, through rational design of a multidentate chiral N-heterocyclic carbene (NHC) ligand and a modular building strategy, we synthesize a series of enantiopure Au(I)-Cu(I) clusters with exceptional stability. Modulation of the ligands stabilize the chiral excited states of clusters to allow thermally activated delayed fluorescence, resulting in the highest orange-red photoluminescence quantum yields over 93.0% in the solid state, which is accompanied by circularly polarized luminescence. Based on the solution process, a prototypical orange-red CP-OLED with a considerably high external quantum efficiency of 20.8% is prepared. These results demonstrate the extensive designability of chiral NHC ligands to stabilize polymetallic clusters for high performance in chiroptical applications.

Efficient X-ray luminescence imaging with ultrastable and eco-friendly copper(I)-iodide cluster microcubes

The advancement of contemporary X-ray imaging heavily depends on discovering scintillators that possess high sensitivity, robust stability, low toxicity, and a uniform size distribution. Despite significant progress in this field, the discovery of a material that satisfies all of these criteria remains a challenge. In this study, we report the synthesis of monodisperse copper(I)-iodide cluster microcubes as a new class of X-ray scintillators. The as-prepared microcubes exhibit remarkable sensitivity to X-rays and exceptional stability under moisture and X-ray exposure. The uniform size distribution and high scintillation performance of the copper(I)-iodide cluster microcubes make them suitable for the fabrication of large-area, flexible scintillating films for X-ray imaging applications in both static and dynamic settings.

2-Mercaptobenzimidazole Functionalized Copper Nanoparticles Fluorescence Probe for Sensitivity and Selectivity Detection of Cys in Serum

In this paper, a 2-mercaptobenzimidazole-copper nanoparticles (MBI-CuNPs) fluorescent probe with high performance based on 2-mercaptobenzimidazole functionalized copper nanoparticles was synthesized by a hydrothermal method and used for cysteine (Cys) detection in serum. The MBI-CuNPs probe exhibits strong fluorescence emission at 415 nm under the excitation at 200 nm, which is attributed to the metal-ligand charge transfer (MLCT) transition through the coordination of an MBI ligand and monovalent copper. Furthermore, the MBI-CuNPs probe has a high quenching fluorescence response to Cys, and shows a good linearity relationship with Cys in 0.05-65 µM, with a detection limit of 52 nM. Moreover, the MBI-CuNPs probe could eliminate the interference of biological mercaptan Hcy and GSH with a similar structure and reaction properties, due to the strong electron-donating ability of Cys, which can quench the fluorescence of the MBI-CuNPs probe. The MBI-CuNPs probe was applied to the analysis of Cys in real serum, and the absolute recovery rate was as high as 90.23-97.00%. Such a fluorescent probe with high sensitivity and selectivity has potential applications for the early prevention of various diseases caused by abnormal Cys levels.

Intramolecular charge transfer enables highly-efficient X-ray luminescence in cluster scintillators

Luminescence clusters composed of organic ligands and metals have gained significant interests as scintillators owing to their great potential in high X-ray absorption, customizable radioluminescence, and solution processability at low temperatures. However, X-ray luminescence efficiency in clusters is primarily governed by the competition between radiative states from organic ligands and nonradiative cluster-centered charge transfer. Here we report that a class of Cu₄I₄ cubes exhibit highly emissive radioluminescence in response to X-ray irradiation through functionalizing biphosphine ligands with acridine. Mechanistic studies show that these clusters can efficiently absorb radiation ionization to generate electron-hole pairs and transfer them to ligands during thermalization for efficient radioluminescence through precise control over intramolecular charge transfer. Our experimental results indicate that copper/iodine-to-ligand and intraligand charge transfer states are predominant in radiative processes. We demonstrate that photoluminescence and electroluminescence quantum efficiencies of the clusters reach 95% and 25.6%, with the assistance of external triplet-to-singlet conversion by a thermally activated delayed fluorescence matrix. We further show the utility of the Cu₄I₄ scintillators in achieving a lowest X-ray detection limit of 77 nGy s^-1 and a high X-ray imaging resolution of 12 line pairs per millimeter. Our study offers insights into universal luminescent mechanism and ligand engineering of cluster scintillators.

Syntheses, Structures, and Photoluminescence of Copper-Based Halides

Copper-based halides have been found to be a new family of lead-free materials with high stability and superior optoelectrical properties. In this work, we report the photoluminescence of the known (C₈H₁₄N₂)CuBr₃ and the discovery of three new compounds, (C₈H₁₄N₂)CuCl₃, (C₈H₁₄N₂)CuCl₃·H₂O, and (C₈H₁₄N₂)CuI₃, which all exhibit efficient light emissions. All these compounds have monoclinic structures with the same space group (P2₁/c) and zero-dimensional (0D) structures, which can be viewed as the assembly of promising aromatic molecules and different copper halide tetrahedrons. Upon the irradiation of deep ultraviolet light, (C₈H₁₄N₂)CuCl₃, (C₈H₁₄N₂)CuBr₃,_, and (C₈H₁₄N₂)CuI₃ show green emission peaking at ∼520 nm with a photoluminescent quantum yield (PLQY) of 3.38, 35.19, and 17.81%, while (C₈H₁₄N₂)CuCl₃·H₂O displays yellow emission centered at ∼532 nm with a PLQY of 2.88%. A white light-emitting diode (WLED) was successfully fabricated by employing (C₈H₁₄N₂)CuBr₃ as a green emitter, demonstrating the potential of copper halides for applications in the green lighting field.

Smart Reversible Transformations between Chiral Superstructures of Copper Clusters for Optical and Chiroptical Switching

Superstructures made from nanoscale clusters with new collective properties are promising in high-tech applications; however, chiral superstructures remain elusive, and the limited intercluster coupling effect at room temperature hampers the tailoring of collective properties. Here, we show that from chiral monomeric copper clusters to two enantiomeric pairs of supercrystals with distinct phases, the absorption band edge red-shifts by over 1.3 eV, with photoluminescence and circularly polarized phosphorescence from visible (572 nm) to near-infrared (NIR, 858 nm). These supercrystals with high NIR quantum yields of up to 45% at room temperature are prototyped for night-vision imaging. In response to solvent and temperature stimuli, chiral supercrystal-to-supercrystal transformations occurred, concomitant with high-contrast optical/chiroptical switching. In situ single-crystal X-ray diffraction (SCXRD), steady-state and time-resolved optical spectroscopy, and response experiments combined with theoretical calculations demonstrate that distance-sensitive intercluster orbital interactions contribute to the exceptional collective optical responses. Such chiral supercrystals built from subnanoscale metal clusters with novel collective chiroptical responses would be useful in the fields of information storage and NIR optical devices.

One-Dimensional Chiral Copper Iodide Chain-Like Structure Cu4 I4 (R/S-3-quinuclidinol)3 with Near-Unity Photoluminescence Quantum Yield and Efficient Circularly Polarized Luminescence

Chiral organic-inorganic hybrid metal halide materials have shown great potential for circularly polarized luminescence (CPL) related applications for their tunable structures and efficient emissions. Here, this work combines the highly emissive Cu₄ I₄ cubane cluster with chiral organic ligand R/S-3-quinuclidinol, to construct a new type of 1D Cu-I chains, namely Cu₄ I₄ (R/S-3-quinuclidinol)₃ , crystallizing in noncentrosymmetric monoclinic P2₁ space group. These enantiomorphic hybrids exhibit long-term stability and show bright yellow emission with a photoluminescence quantum yield (PLQY) close to 100%. Due to the successful chirality transfer from the chiral ligands to the inorganic backbone, the enantiomers show intriguing chiroptical properties, such as circular dichroism (CD) and CPL. The CPL dissymmetry factor (g_lum ) is measured to be ≈4 × 10^-3 . Time-resolved photoluminescence (PL) measurements show long averaged decay lifetime up to 10 µs. The structural details within the Cu₄ I₄ reveal the chiral nature of these basic building units, which are significantly different than in the achiral case. This discovery provides new structural insights for the design of high performance CPL materials and their applications in light emitting devices.

Interaction of N-nitrosamines with binuclear copper complexes for luminescent detection

Cu(I) from tetrakis(acetonitrile)copper(I) hexafluorophosphate ([Cu(MeCN)₄]PF₆) was complexed with five structurally related phosphines containing N-heterocycles. The interactions between the resulting complexes and some N-nitrosamines were studied using X-ray crystallography as well as emission spectroscopy. Upon complexation, three phosphine ligands bridge two Cu(I) centers to give paddlewheel type structures that displayed a range of emission wavelengths spanning the visible region. N-Nitrosodimethylamine (NDMA) was shown to coordinate to one of the two copper centers in some of the paddlewheel complexes in the solid state and this interaction also quenches their emissions in solution. The influence of the weakly coordinating anion on crystal and spectroscopic properties of one of the paddlewheel complexes was also examined using tetrakis(acetonitrile)copper(I) perchlorate ([Cu(MeCN)₄]ClO₄) as an alternative Cu(I) source. Similarly, copper(II) perchlorate hexahydrate (Cu(ClO₄)₂·6H₂O) was used for complexation to observe the impact of metal oxidation state on the two aforementioned properties. Lastly, the spectroscopic properties of the complex between Ph₂P(1-Isoquinoline) and Cu(I) was shown to exhibit solvent dependence when the counterion is ClO₄^-. These Cu(I) complexes are bench stable solids and may be useful materials for developing a fluorescence based detection method for N-nitrosamines.

A family of CuI-based 1D polymers showing colorful short-lived TADF and phosphorescence induced by photo- and X-ray irradiation

Exploiting 2-(alkylsulfonyl)pyridines as 1,3-N,S-ligands, herein we have constructed 1D CuI-based coordination polymers (CPs) bearing unprecedented (CuI)_n chains and possessing remarkable photophysical properties. At room temperature, these CPs show efficient TADF, phosphorescence or dual emission in the deep-blue to red range with outstandingly short decay times of 0.4-2.0 μs and good quantum performance. Owing to great structural diversity, the CPs demonstrate a variety of emissive mechanisms, spanning from TADF of ¹(M + X)LCT type to ³CC and ³(M + X)LCT phosphorescence. Moreover, the designed compounds emit strong X-ray radioluminescence with the quantum efficiency of up to an impressive 55% relative to all-inorganic BGO scintillators. The presented findings push the boundaries in designing TADF and triplet emitters with very short decay times.

Highly Effective Hybrid Copper(I) Iodide Cluster Emitter with Negative Thermal Quenched Phosphorescence for X-Ray Imaging

The low efficiency triplet emission of hybrid copper(I) iodide clusters is a critical obstacle to their further practical optoelectronic application. Herein, we present an efficient hybrid copper(I) iodide cluster emitter (DBA)₄ Cu₄ I₄ , where the cooperation of excited state structure reorganization and the metallophilicity interaction enables ultra-bright triplet yellow-orange emission with a photoluminescence quantum yield over 94.9 %, and the phonon-assisted de-trapping process of exciton induces the negative thermal quenching effect at 80-300 K. We also investigate the potential of this emitter for X-ray imaging. The (DBA)₄ Cu₄ I₄ wafer demonstrates a light yield higher than 10⁴  photons MeV^-1 and a high spatial resolution of ≈5.0 lp mm^-1 , showing great potential in practical X-ray imaging applications. Our new copper(I) iodide cluster emitter can serve as a model for investigating the thermodynamic mechanism of photoluminescence in hybrid copper(I) halide phosphorescence materials.

Solution-Processable Copper Halide Based Hybrid Materials Consisting of Cationic Ligands with Different Coordination Modes

Using cationic ligands containing both aromatic and aliphatic coordination sites, we have synthesized and structurally characterized five new CuX-based hybrid materials consisting of anionic inorganic motifs that also form coordinate bonds with the cationic organic ligands. As a result of the unique bonding nature at the inorganic/organic interfaces, these compounds demonstrate strong resistance toward heat and can be readily processed in solution. They emit light in the visible region ranging from cyan to yellow color, with the highest photoluminescence quantum yield (PLQY) reaching 71%. The influence of the different coordination modes of the ligands on their emission behavior was investigated employing both experimental and theoretical methods, which have provided insight in understanding structure-property relationships in these materials and guidelines for tuning and enhancing their chemical and physical properties.

A high-performance fluorescent probe for detection of cysteine in plasma constructed by combining Cu(I) and 2,5-dimercapto-1,3,4-thiadiazole

A high-performance fluorescent probe 2,5-dimercapto-1,3,4-thiadiazole copper nanoparticles (DMTD-CuNPs) was synthesized by hydrothermal method based on monovalent copper (Cu(I)) and 2,5-dimercapto-1,3,4-thiadiazole (DMTD), and it can effectively detect cysteine (Cys) in plasma. Experiments show that DMTD can reduces band gap of Cu(I) in DMTD-CuNPs, promote charge transfer transition from DMTD to Cu(I) and significantly enhance fluorescence intensity of DMTD-CuNPs at 515 nm. The large Stokes shift of DMTD-CuNPs is 315 nm, which can reduce the self-quenching of probe fluorescence and improves detection accuracy of the probe. In the presence of Cys, fluorescence of DMTD-CuNPs at 515 nm is significantly quenched because Cys reacts with Cu(I) in DMTD-CuNPs through Cu-S bond to form reduced charge transfer, which can be successfully used for the detection of Cys. Linear range and detection limit for Cys detection are 25-65 µM and 50 nM, respectively. Furthermore, feasibility of detecting Cys in plasma using DMTD-CuNPs probe was evaluated by standard addition method, and the absolute recovery is 96-99%. Such a DMTD-CuNPs probe shows high sensitivity, good selectivity and low detection limit for Cys, which is expected to be used for the practical analysis of Cys in plasma.

Carborane-thiol protected copper nanoclusters: stimuli-responsive materials with tunable phosphorescence

Atomically precise nanomaterials with tunable solid-state luminescence attract global interest. In this work, we present a new class of thermally stable isostructural tetranuclear copper nanoclusters (NCs), shortly Cu4@oCBT, Cu4@mCBT and Cu4@ICBT, protected by nearly isomeric carborane thiols: ortho-carborane-9-thiol, meta-carborane-9-thiol and ortho-carborane 12-iodo 9-thiol, respectively. They have a square planar Cu4 core and a butterfly-shaped Cu4S4 staple, which is appended with four respective carboranes. For Cu4@ICBT, strain generated by the bulky iodine substituents on the carboranes makes the Cu4S4 staple flatter in comparison to other clusters. High-resolution electrospray ionization mass spectrometry (HR ESI-MS) and collision energy-dependent fragmentation, along with other spectroscopic and microscopic studies, confirm their molecular structure. Although none of these clusters show any visible luminescence in solution, bright μs-long phosphorescence is observed in their crystalline forms. The Cu4@oCBT and Cu4@mCBT NCs are green emitting with quantum yields (Φ) of 81 and 59%, respectively, whereas Cu4@ICBT is orange emitting with a Φ of 18%. Density functional theory (DFT) calculations reveal the nature of their respective electronic transitions. The green luminescence of Cu4@oCBT and Cu4@mCBT clusters gets shifted to yellow after mechanical grinding, but it is regenerated after exposure to solvent vapour, whereas the orange emission of Cu4@ICBT is not affected by mechanical grinding. Structurally flattened Cu4@ICBT didn't show mechanoresponsive luminescence in contrast to other clusters, having bent Cu4S4 structures. Cu4@oCBT and Cu4@mCBT are thermally stable up to 400 °C. Cu4@oCBT retained green emission even upon heating to 200 °C under ambient conditions, while Cu4@mCBT changed from green to yellow in the same window. This is the first report on structurally flexible carborane thiol appended Cu4 NCs having stimuli-responsive tunable solid-state phosphorescence.

Novel 1,2,3-triazolyl phosphine with a pyridyl functionality: synthesis, coinage metal complexes, photophysical studies and Cu(I) catalyzed C-O coupling of phenols with aryl bromides

This manuscript describes the synthesis and coinage metal complexes of pyridine appended 1,2,3-triazolyl-phosphine [2-{(C₆H₄N)(C₂(PPh₂)N₃C₆H₅)}] (1), photophysical studies and their catalytic application. The reactions of 1 with copper salts afforded dimeric complexes [{Cu(μ₂-X)}₂{2-(C₆H₄N)(C₂(PPh₂)N₃C₆H₅)}₂] (2, X = Cl; 3, X = Br; and 4, X = I). The crystal structure indicates that the Cu⋯Cu distance in 4 (2.694 Å) is significantly shorter than that in complexes 3 (3.0387 Å) and 2 (3.104 Å), indicating strong cuprophilic interactions which is also supported by NBO calculations, signifying the involvement of 3d_z² orbitals from each Cu atom contributing to the bonding interaction. The fluorescence studies on complexes 2-4 carried out in the solid state showed broad emission bands around 560 nm on excitation at λ_ex = 420 nm. Complex 4 on treatment with two equivalents of 1,10-phenanthroline yielded a mononuclear complex 5 which showed almost complete quenching of fluorescence in the solid state, clearly indicating that the emissive properties of 4 are mainly due to the Cu⋯Cu interaction, along with (M + X)LCT. The reactions of 1 with silver salts led to the isolation of dimeric complexes [{Ag(μ₂-X)}₂{2-(C₆H₄N)(C₂(PPh₂)N₃C₆H₅)}₂] (6, X = Cl; 7, X = Br; and 8, X = I) in good yield. The reaction between 1 and [AuCl(SMe₂)] yielded [{AuCl}{2-(C₆H₄N)(C₂(PPh₂)N₃C₆H₅)}] (9). The molecular structures of 2-5 and 7-9 were confirmed by single crystal X-ray analysis. The complex 4 is found to be an excellent catalyst for C-O coupling under mild conditions.

Synthesis, Electrochemistry, Photophysics, and Photochemistry of a Discrete Tetranuclear Copper(I) Sulfido Cluster

A tetranuclear copper(I) complex, [Cu₄{μ-(Ph₂P)₂NH}₄(μ₄-S)](PF₆)₂ (1), was synthesized. It was found to display intense and long-lived phosphorescence in the solid and solution states. The lowest-energy excited state was assigned as ligand-to-metal charge transfer (LMCT) [S^2- → Cu₄] mixed with some metal-centered (ds/dp) character. In addition, the phosphorescent state of this complex was found to be quenched by pyridinium acceptors via an oxidative electron-transfer quenching process. An excited-state reduction potential of -1.74 V versus saturated salt calomel electrode was estimated through oxidative quenching studies with a series of structurally related pyridinium acceptors, indicative of its strong reducing power in the excited state. From the transient absorption difference spectrum of the tetranuclear copper(I) sulfido complex and 4-(methoxycarbonyl)-N-methylpyridinium hexafluorophosphate, in addition to the characteristic absorption of the pyridinyl radical at ca. 395 nm, two absorption bands at ca. 500 and 660 nm were also observed. The former was assigned as an LMCT absorption [S^2- → Cu₄] and the latter as an intervalence charge-transfer transition, associated with the mixed-valence species Cu^I/Cu^I/Cu^I/Cu^II.

Synthesis and Photophysical Properties of Heavier Pnictogen Complexes

Recent success in the synthesis of π-conjugated heavier pnictogen (As, Sb, and Bi) compounds and their transition metal complexes has led to the current surge in interest that led to significant development in the field of photophysical and optoelectronic properties of heavier pnictogens and their transition metal complexes. The presence of heavier pnictogens (As, Sb and Bi) in the molecular skeleton promotes inter-system crossing (ISC) and reverse inter-system crossing (RISC), because of the heavy atom effect, via altering the intermolecular interactions and orbital energy levels. As a result, π-conjugated heavier pnictogen compounds such as arsines, dibenzoarsepins, arsinoquinoline, heterofluorene, benzo[b]heterole (heterole=arsole, bismole, and stibole) show unique optoelectronic properties such as narrow bandgap, low-energy absorption, and long-wavelength emission than lighter pnictogen-based compounds. This review focuses on recent advances in the synthesis and photophysical properties of heavier pnictogen compounds. The synthesis and photophysical properties of heavier pnictogens are discussed and elaborated.

Structure and emission properties of dinuclear copper(i) complexes with pyridyltriazole

A new series of five highly emissive binuclear heteroleptic pyridyltriazole-Cu(i)-phosphine complexes 1-5 was synthesized and examined by different experimental (IR, elemental and thermogravimetric analysis, single crystal X-ray diffraction technique, UV-vis and fluorescence spectroscopy) and quantum chemical aproaches. Complexes 1-5 exhibited excellent stimuli-responsive photoluminescent performance in the solid state at room temperature (quantum yield (QY) = 27.5-52.0%; lifetime (τ) = 8.3-10.7 μs) and when the temperature was lowered to 77 K (QY = 38.3-88.2; τ = 17.8-134.7 μs). The highest QY was examined for complex 3 (52%) that can be explained by the small structural changes between the ground S₀ and exited S₁ and T₁ states leading to the small S₁-T₁ triplet gap and efficient thermally-activated delayed fluorescence. Moreover, complex 4 demonstrates reversible mechanochromic and excitation dependent luminescence.

Sky Blue and Yellow Cluster Light-Emitting Diodes Based on Asymmetric Cu4I4 Nanocubes

Controllably optimizing excited-state characteristics is crucial for luminescent nanoclusters but remains a formidable challenge. Herein, we report an effective "ligand-induced asymmetrization" strategy for constructing thermally activated delayed fluorescence-featured cubic Cu4I4 nanoclusters with asymmetric configurations, named [tBCzDBFDP]2Cu4I4 and [PTZDBFDP]2Cu4I4. Through changing 3,6-di-tert-butyl-carbazole (tBCz) to phenothiazine (PTZ) with a stronger electron-donating effect, emission color is tuned from greenish blue of [tBCzDBFDP]2Cu4I4 to yellow of [PTZDBFDP]2Cu4I4, as well as the triplet locally excited state of the former to the triplet charge transfer state of the latter. Temperature-correlated spectroscopic investigation indicates that in terms of triplet quenching suppression, [tBCzDBFDP]2Cu4I4 is superior to [PTZDBFDP]2Cu4I4, in accord with the stabilities of their triplet locally excited state and triplet charge transfer state. As a consequence, these asymmetric Cu4I4 nanocubes endowed their cluster light-emitting diodes with the external quantum efficiencies beyond 12% for sky blue and 8% for yellow. These results suggest the significance and effectiveness of ligand engineering for optoelectronic nanoclusters.

An Insight into nd10 Metal Cyanide-based Coordination Polymers Through ab-initio Calculations: Electronic Properties and Optical Response

Semiconductors are essential for modern life since they are the basis of many current technologies that are related to better living standards. Some of them, characterized by the periodic assembling of metal cyanides with filled d-shell (nd¹⁰ ) constitute an interesting series of cyanide-based coordination polymers with physical properties such like anomalous anisotropic thermal expansion and quantum confinement effects related to the polymer's width that can be exploited for technological applications. Herein, the electronic structure of nd¹⁰ metal cyanide-based systems were studied both experimentally and through Density Functional Theory. The band gap found for one-dimensional (1D) -M-C≡N- (M=Cu, Ag, Au) and tetrahedral M-(C≡N)₂ (M=Zn, Cd, Hg) systems can be attributed to Laporte-allowed π → ${\to }$ π* (Metal to Ligand Charge Transfer mechanism) combined with metal center (d → ${\to }$ s,p) electronic transitions. Aurophilic bonding was found on the AuCN structure, and a new forbidden electronic transition associated to its band gap is reported. Computed effective and reduced masses from carriers revealed that carrier mobility and quantum confinement effects are greater in 1D systems.