Cuprous Halides Research Articles

Organic-Inorganic Hybrid Cuprous Halide Scintillators for Flexible X-ray Imaging.

Recently, organic-inorganic hybrid scintillators have received more and more attention because of their merits of easy preparation, good stability, and nontoxicity. Considering the high cost of traditional inorganic scintillators, here we describe experimental investigations of a low-cost zero-dimensional scintillator comprising organic-inorganic hybrid cuprous halide and its capabilities for sensitive X-ray detection and flexible X-ray imaging. This scintillator is synthesized using a facile antisolvent diffusion method with large scalability (50 g). The crystal structure shows an unreported plane rhombus cuprous halide core, which also demonstrates outstanding photoluminescence with a high quantum yield (99.5%), excellent radioluminescence with an efficient internal light yield (25 000 photon/MeV), and sensitive X-ray response with a low detection limit (40.4 nGy/s). The organic-inorganic hybrid chemical feature allows the fabrication of a flexible film based on this scintillator for fine-resolution X-ray radiography. These advantages endow our organic-inorganic hybrid scintillator with promising potential in wearable and portable medical devices.

Zero‐Dimensional Organic Copper(I) Iodide Hybrid with High Anti‐Water Stability for Blue‐Light‐Excitable Solid‐State Lighting

AbstractThe discovery of rare‐earth free luminescent materials with blue‐light‐excitable characteristic is of great importance for solid‐sate lighting applications. Herein, a Cu(I)‐based 0D luminescent hybrid (1,3‐dppH2)2Cu4I8∙H2O is synthesized by a facile solution method, and it shows the orange‐red emission peaking at 625 nm upon 460 nm excitation. The structure‐related luminescence mechanism has been elaborated by experimental and theoretical investigations. Moreover, the emission intensity remains unchanged even after continuous water treatment for 60 days due to the improved structural stability originating from intermolecular π–π interaction between organic cations. A warm white light‐emitting diode (LED) device with the color rendering index of 91.4% has been fabricated by combining the 440 nm LED chip, green‐emitting Lu3Al5O12:Ce3+, and (1,3‐dppH2)2Cu4I8∙H2O. This work provides a new design route towards 0D cuprous halide materials and will initiate more exploration of their intrinsic luminescence mechanism.

Versatile, Rapid, and Plasma‐Assisted Synthesis of Cuprous Halide Composites at Room Temperature and Pressure (Adv. Mater. Technol. 4/2022)

Liquid Halogenated Molecules Under exposure to atmospheric pressure dielectric barrier discharge plasma, liquid halogenated molecules react on a copper surface to form cuprous halide (CuX) nanocrystals with a composition defined by the halogens in the precursor molecule, enabling a range of CuX products through a rapid, simple process by Jennifer MacLeod and coworkers in article number 2100509.

Pure White Emission with 91.9% Photoluminescence Quantum Yield of [(C3H7)4N]2Cu2I4 out of Polaronic States and Ultra-High Color Rendering Index.

Recently, cuprous halide perovskite-type materials have drawn tremendous attention for their intriguing optical properties. Here, a zero-dimensional (0D) Cu(I)-based compound of [(C3H7)4N]2Cu2I4 ([C3H7)4N]+ = tetrapropylammonium cation) was synthesized by a facile solution method, a monoclinic system of P21/n symmetry with a Cu2I42- cluster as the confined structure. The as-synthesized [(C3H7)4N]2Cu2I4 exhibits bright dual-band pure white emission with a photoluminescence quantum yield (PLQY) of 91.9% and CIE color coordinates of (0.33, 0.35). Notably, this compound also exhibits an ultrahigh color rendering index (CRI) of 92.2, which is comparable to the highest value of single-component metal halides reported recently. Its Raman spectra provide a clear spectral profile of strong electron-phonon interaction after [(C3H7)4N]+ incorporation, favoring the self-trapped exciton (STE) formation. [(C3H7)4N]2Cu2I4 can give dual-STE bands at the same time because of the Cu-Cu metal bond in a Cu2I42- cluster, whose populations could be scaled by temperature, together with the local dipole orientation modulation of neighboring STEs and phase transition related emission color coordinate change. Particularly, the outstanding chemical- and antiwater stability of this compound was also demonstrated. This work illustrates the potential of such cuprous halide perovskite-type materials in multifunctional applications, such as lighting in varied environments.

Star-shaped Pd(II) and Pt(II) complexes containing C3-symmetric conjugated thiophenes: Synthesis, characterization, and chemical reactions with organic unsaturated molecules

Triple oxidative addition reactions of [M0(styrene)(PMe3)2] (M = Pd/Pt) with C3-symmetric star-shaped molecules containing 1-, 3-, and 5-thiophene-substituted benzene, in 1:0.3 ratio, afforded new Pd(II) and Pt(II) trinuclear complexes in suitable yields. Analogous trinuclear complexes were formed by similar reactions of thiophenyl halide derivatives containing triazine or triphenylamine cores. Alternatively, a trinuclear Pd(II) complex was obtained by oxidative addition of a Pd(0) complex (synthesized from allyl(cyclopentadienyl) palladium(II), [(η5-C5H5)Pd(η3-C3H5)] with PEt3. Sonogashira-type coupling between trinuclear Pt(II) halides (containing C3-symmetric conjugated thiophenes) and alkynes, in the presence of cuprous halide and diethylamine, afforded alkynyl-containing trinuclear Pt(II) complexes with extended π-conjugation. Insertion reactions of organic isocyanides (CN-R) with trinuclear Pd(II) complexes yielded trinuclear Pd(II) imidoyl complexes by insertion of CN-R into Pd-carbon (thiophene) bonds. Reactions of trinuclear Pt(II) halides with Ag(OCOCF3) and NaN3 formed pseudohalogen-containing Pt(II) complexes.

Band gap anomaly in cuprous halides

Unlike the conventional zinc-blende II-VI and III-V common-cation systems, which exhibit a general trend of decreasing band gap with increasing anion atomic number, the zinc-blende I-VII cuprous halides CuX (X = Cl, Br, and I) all have an approximately equal direct band gap. Here, using first-principles calculations, we demonstrate that this band gap anomaly in Cu halides is attributed to the unique energy level order of Cu 3d well above X p, making the valence band maximum (VBM) an antibonding state derived mostly from the Cu 3d orbital, thus, a relatively small variation of the band gap with respect to the anion atomic number.

Versatile, Rapid, and Plasma‐Assisted Synthesis of Cuprous Halide Composites at Room Temperature and Pressure

AbstractCuprous halides (CuX) are transparent semiconductors with a range of appealing characteristics, and with targeted applications in electronics, energy storage, and sensing. Here, it is demonstrated that CuX films can be formed at room temperature and atmospheric pressure using a rapid, plasma‐based approach. Crystalline CuX products are formed using dielectric barrier discharge plasma to react liquid small‐molecule precursors (1,2‐dichloro‐4‐X‐benzene, where X = Cl, Br, and I) with a copper substrate via a plasma‐assisted reaction. This process produces a composite film, containing both an organic polymer and the cuprous halide crystallites, with a hierarchical nanostructure. The cuprous halides have the zincblende structure, with sizes ranging from ≈10 to ≈85 nm. By employing either neat or mixed precursors, products including CuCl, CuBr, CuCl0.1I0.9, and CuBr0.5I0.5 are accessed. Furthermore, the same process can be used to produce AgI films from the iodated precursor molecule on a silver film, demonstrating the remarkable versatility of this approach. This work reveals a flexible new method to produce these technologically relevant I–VII semiconductor films, which can have applications in sensing, batteries, or photovoltaics.

Accuracy trade-off between one-electron and excitonic spectra of cuprous halides in first-principles calculations.

Because of the sophisticated error cancellation in the density functional theory (DFT)-based calculations, a theoretically more accurate input would not guarantee a better output. In this work, our first-principles GW plus Bethe-Salpeter equation calculations using pseudopotentials show that cuprous halides (CuCl and CuBr) are such extreme cases for which a better one-electron band is not accompanied with a better exciton binding energy. Moreover, we find that the exchange interaction of Cu core electrons plays a crucial role in their ground-state electronic properties, especially in the energy gap and macroscopic dielectric constant. Our work provides new insights into the understanding of the electronic structure of cuprous halides from the DFT perspective.

The superiority of cuprous chloride to iodide in the selective aerobic oxidation of benzylic alcohols at ambient temperature

Cuprous halides, best described as (CuX)n (X = Cl−, Br−, and I−) in their solid state, catalyse selective aerobic oxidation of alcohols with the assistance of both NMI (N‐methylimidazole) and TEMPO (2,2,6,6‐tetramethylpiperidine‐1‐oxyl), and the iodide generally demonstrates the highest activity, for example, in the oxidation of 1‐octanol at ambient temperature under 24 h' reaction. However, in the aerobic oxidation of benzylic alcohols, the chloride showed superiority to the iodide in that the aerobic oxidation was quantitatively completed within 3 h at ambient temperature whereas the iodide showed only about half the activity of the chloride analogue. By probing the system using electrochemistry, electric conductivity, and 1H NMR titration, it was revealed that the surprising anomaly was due to the difference in the rate of forming active species, [Cu (NMI)2X(MeCN)], from the polymeric solid in a two‐stage process. Substrates expansion of 11 benzylic alcohols indicated that CuCl/NMI/TEMPO system demonstrated quantitative conversion of benzylic alcohols into corresponding aldehydes within 3 h and showed great tolerance to the substituents on the phenyl ring of the substrates. Furthermore, electron‐withdrawing substituent was beneficial to the oxidation and could offset the steric effect at orthro‐substituent. Such a behaviour suggested that in the catalysis, increasing the acidity of the hydroxyl group (OH) of the substrates could ease the oxidation, which implied that the deprotonation via an internal pathway might be one of the rate‐determining steps. Our results also showed that the anion halide participated actively in the catalysis by coordinating to Cu(I) in the active species.

N-Heterocyclic Carbenes–Cu

The electronic structures of N-heterocyclic carbenes (NHC) imidazolinylidene, thiazolinylidene, imidazolylidene, thiazolylidene, and 1,2,4-triazolylidene and their complexes with cuprous halides (CuX, X = Cl, Br, I) were investigated theoretically at the B3LYP/def2-SVP level. In contrast to other NHCs, imidazolylidene and 1,2,4-triazolylidene do not dimerize owing to the negligible coefficient of the vacant p-orbital at the carbene centre in their respective LUMOs. This is further supported by their greater thermodynamic and kinetic stabilities revealed by greater activation free energies and smaller standard free energies for their dimerization. Second-order perturbation interactions in the natural bond orbital (NBO) analysis of the NHCs indicate that six π electrons are delocalized in imidazolylidene, thiazolylidene, and 1,2,4-triazolylidene, conferring aromatic character and thereby enhancing their thermodynamic stability. NBO analysis reveals the existence of effective back bonding from a d orbital of Cu to the NHC, increasing the Wiberg bond index of the C–Cu bond to ~1.5. Owing to the large electronic chemical potential (μ) and high nucleophilicity indices, NHCs are able to transfer their electron density effectively to the cuprous halides having low μ values and high electrophilicity indices to yield stable NHC–CuI complexes. Large values of the Fukui function f(r) at the carbene centre of the NHCs and Cu atom of the NHC–CuI complexes indicate their softness. Imidazolylidene was found to be the softest, rationalizing wide use of this class of NHCs as ligands. The coordination of the NHCs to cuprous halides is either barrierless or has a very low activation free energy barrier. In the A3 reaction wherein NHC–Cu(I) complexes are used as catalyst, the reaction of NHC–CuI with phenylacetylene changes the latter into acetylide accompanied by raising the energy level of its HOMO considerably compared with the level of the uncomplexed alkyne, making its reaction with benzaldehyde barrierless.

First-Principles Study of Anharmonic Lattice Dynamics in Low Thermal Conductivity AgCrSe_{2}: Evidence for a Large Resonant Four-Phonon Scattering.

We report a study of the anharmonic lattice dynamics in low lattice thermal conductivity (κ_{l}) material AgCrSe_{2} by many-body perturbation theory. We demonstrate surprisingly giant four-phonon scattering exclusive for the heat-carrying transverse acoustic phonons due to large quartic anharmonicity and nondispersive phonon band structure, which lead to four-phonon Fermi resonance and breaks the classical τ^{-1}∼ω^{m}T^{n} relation for phonon-phonon interactions. This strong resonant scattering extends over the Brillouin zone and substantially suppresses the thermal transport, even down to a low temperature of 100K. The present results provide fundamental insights into the four-phonon resonant dynamics in the low-κ_{l} system with flat phonon dispersions, i.e., cuprous halides and skutterudites.

Coordination-Bond-Driven Dissolution-Recrystallization Structural Transformation with the Expansion of Cuprous Halide Aggregate.

Metal-organic frameworks (MOFs) with cuprous-halide-aggregates have shown superiority as organic LED (OLED) and semiconductor materials, while engineering MOF flexibility by involving the expansion of cuprous aggregates remains a great challenge. In this particular work, a dissolution-recrystallization structural transformation (DRST) with the dramatic growth of CuI-I aggregates, from 2D NJNU-100 to 3D NJNU-101 has been successfully realized. The unsaturated coordination nodes (2-positional nitrogen atoms) in NJNU-100 have been demonstrated to be the driven force for DRST to NJNU-101 via the formation of coordination bonds. The structural transformation process was irreversible and observed with optical microscopy and powder XRD. The expansion of CuI-I aggregates was also computational simulated accompanying with the rotation of the neutral tripodal TTTMB ligand (1,3,5-tris(1,2,4-triazol-1-ylmethyl)-2,4,6-trimethylbenzene) and the reduction of CuII to CuI. Moreover, the intermediate product NJNU-102 was captured by adding the planar molecular anthrancene to shut down the reaction, where only partial 2-positional nitrogen atoms coordinated to the aggregates and the anthrancene was oxidized to anthraquinone. NJNU-102 has further confirmed that DRST involved the breakage and recombination of coordination bonds and the electron transfer. NJNU-100 and NJNU-101 could be applied as semiconductor and OLED materials. This work has provided insights for crystal engineering, especially for the construction of the CuIxXy aggregates, and illustrated that DRST could be controlled with a rational design (as the unsaturated coordination modes).

Carboxylation of Alkenyl Boronic Acids and Alkenyl Boronic Acid Pinacol Esters with CO2 Catalyzed by Cuprous Halide

A cuprous halide catalysed carboxylation of alkenyl boronic acids and alkenyl boronic acid pinacol esters under CO2, affording the corresponding α, β‐unsaturated carboxylic acids in good yield, has been developed. The potassium (E)‐trifluoro(styryl)borate is also compatible with this reaction. This simple and efficient copper(I) catalytic system showed good functional group tolerance.

Intrinsically p-type cuprous iodide semiconductor for hybrid light-emitting diodes

Cuprous halides, characterized by a direct wide band-gap and a good lattice matching with Si, is an intrinsic p-type I-VII compound semiconductor. It shows remarkable optoelectronic properties, including a large exciton binding energy at room temperature and a very small piezoelectric coefficient. The major obstacle to its application is the difficulty in growing a single-crystal epitaxial film of cuprous halides. We first demonstrate the single crystal epitaxy of high quality cuprous iodide (CuI) film grown on Si and sapphire substrates by molecular beam epitaxy. Enhanced photoluminescence on the order of magnitude larger than that of GaN and continuous-wave optically pumped lasing were found in MBE grown CuI film. The intrinsic p-type characteristics of CuI were confirmed using an n-AlGaN/p-CuI junction that emits blue light. The discovery will provide an alternative way towards highly efficient optoelectronic devices compatible with both Si and III-nitride technologies.

Giant pressure-enhancement of multiferroicity in CuBr2

Type-II multiferroic materials, in which ferroelectric polarization is induced by inversion non-symmetric magnetic order, promise new and highly efficient multifunctional applications based on the mutual control of magnetic and electric properties. Although this phenomenon has to date been limited to low temperatures, here we report a giant pressure-dependence of the multiferroic critical temperature in CuBr$_2$. At 4.5 GPa, $T_\mathrm{C}$ is enhanced from 73.5 to 162 K, to our knowledge the highest value yet reported for a non-oxide type-II multiferroic. This growth shows no sign of saturating and the dielectric loss remains small under these high pressures. We establish the structure under pressure and demonstrate a 60\% increase in the two-magnon Raman energy scale up to 3.6 GPa. First-principles structural and magnetic energy calculations provide a quantitative explanation in terms of dramatically pressure-enhanced interactions between CuBr$_2$ chains. These large, pressure-tuned magnetic interactions motivate structural control in cuprous halides as a route to applied high-temperature multiferroicity.

Syntheses, crystal structures and visible light driven photocatalytic properties of organic-inorganic hybrid cuprous halides

By using in situ N-alkylating [(Me)2-2,2-bipy]2+ organic cation as structural-directing agent (SDA), two new types of organic-inorganic hybrid cuprous halides, namely, [(Me)2-2,2-bipy]Cu3I5 (1) and [(Me)2-bipy)]2Cu7Br9I2(2), have been solvothermally synthesized and structurally characterized. The compound 1 crystallizes in the monoclinic space group P21/n (No. 147) and features one-dimensional (1D) anionic [Cu3I5]2- chains separated by [(Me)2-2,2-bipy]2+ cations. The structure of compound 2 contains a 1D [Cu7Br9I2]2- anionic chain, which belongs to the first hybrid cuprous halide with mixed halogen elements. The UV–vis absorption optical measurement reveals that the compounds possesses narrow band gaps of 1.95–2.14 ​eV, which leads to stable photocatalytic degradation activity over organic pollutant under visible light irradiation. The possible photocatalytic mechanism and reason of photochemical stability is also proposed based on experimental results and electronic band structural calculation.

Room temperature cupric halides mediated olefin alkoxylation of BODIPYs with methanol: mechanisms and scope.

We disclose an efficient methodology for olefin alkoxylation of fluorescent BODIPYs (boron-dipyrromethene) at the 3,5-styryl group with methanol by cupric halide (chloride or bromide) at room temperature. Mechanistic studies provide evidence for the alkoxylation reaction firstly initiated by a radical cation, that is, halide promotes the oxidizing ability of the Cu(ii) center to an extent that the single electron transfer (SET) from BODIPYs to the cupric ion and results in the production of a BODIPYs radical cation and Cu(i), then the BODIPYs radical cation subsequently reacts with methanol to afford the alkoxylated product. As the dialkoxylated product complexes with cuprous halide and further decreases its reducing ability, which is supported by DFT calculations, only strongly oxidative cupric bromide can mediate tetraalkoxylation and give rise to the tetraalkoxylated product. In addition, the expanded scope studies suggest that this method is also well suited for the alkoxylation of electron-rich conjugated olefins. The active benzyl bromide derivative may be another intermediate in the presence of cupric bromide. Therefore, the reaction is highly dependent on the anions of cupric salts; Cu(OAc)2, CuSO4 and Cu(NO3)2 containing weakly nucleophilic anions show no activity in alkoxylation.

Cuprous cluster as effective single-molecule metallaphotocatalyst in white light-driven C[sbnd]H arylation

This study investigated a series of ferrocenyltelluroether based cuprous halide clusters as effective single-molecule metallaphotocatalysts (SMP) in white light-driven CH arylation at room temperature and air. A systematic mechanistic study reveals that Cu(I) cluster can be irradiated by visible light to promote proton-coupled electron transfer (PCET), during which the electron from Cu(I)* leaves together with the proton from benzothiazole CH, leading to the formation of benzothiazolate-coordinated Cu(II) intermediate and aryl radical. Subsequently, the electron transfer (ET) from the ferrocene unit to the Cu(II) center releases the reactive benzothiazolate to form the target product with aryl radical. The advantages of these copper(I) halide clusters as SMP include high photocatalytic efficiency, structure adjustability, mild reaction conditions and good functional group tolerance.

Rapid and Scalable Synthesis of Cuprous Halide-Derived Copper Nano-Architectures for Selective Electrochemical Reduction of Carbon Dioxide.

Electrochemical reduction of carbon dioxide (CO2) into value-added chemicals and fuels provides a promising pathway for environmental and energy sustainability. Copper (Cu) demonstrates a unique ability to catalyze the electrochemical conversion of CO2 into valuable multicarbon products. However, developing a rapid, scalable and cost-effective method to synthesize efficient and stable Cu catalysts with high selectivity toward multicarbon products at a low overpotential is still hard to achieve and highly desirable. In this work, we present a facile wet chemistry approach to yield well-defined cuprous halide (CuX, X = Cl, Br or I) microcrystals with different degrees of truncations at edges/vertices, which can be ascribed to the oxidative etching mechanism of halide ions. More importantly, the as-obtained cuprous halides can be electrochemically transformed into varied Cu nanoarchitectures, thus exhibiting distinct CO2 reduction behaviors. The CuI-derived Cu nanofibers composed of self-assembled nanoparticles are reported for the first time, which favor the formation of C2+3 products at a low overpotential with a particular selectivity toward ethane. In comparison, the Cu nanocubes evolved from CuCl are highly selective toward C1 products. For CuBr-derived Cu nanodendrites, C1 products are subject to form at a low overpotential, while C2+3 products gradually become dominant with a favorable formation of ethylene when the potential turns more negative. This work explicitly reveals the critical morphology effect of halide-derived Cu nanostructures on the CO2 product selectivity, and also provides an ideal platform to investigate the structure-property relationship for CO2 electroreduction.

Organic cation directed one-dimensional cuprous halide compounds: syntheses, crystal structures and photoluminescence properties.

In recent years, organic-inorganic hybrid metal halides have emerged as a highly promising class of semiconducting light emitting diodes (LEDs) due to their fascinating photoluminescence properties. Here, by specifically selecting different organic cations as templates, a series of new hybrid cuprous halides have been solvothermally prepared, namely [Me-Py]CuI2 (1), [(Me)2-DABCO]Cu2I4 (2), [Me-MePy]Cu2I3 (3), and [H2DABCO]Cu3X5 (X = I (4) and Br (5)). These hybrid cuprous halides feature one-dimensional (1D) [CuI2]-, [Cu2I3]- and [Cu3X5]2- (X = Br, I) chains surrounded and charge-balanced by organic cations. Under UV photoexcitation, these hybrid cuprous halides exhibit strong tunable photoluminescence from cyan (480 nm) to red (675 nm) emissions with large Stokes shifts (345 nm). The intrinsic nature of PL emissions is also investigated based on temperature-dependent PL emission, lifetime, photoluminescence quantum efficiencies, etc.