Cadmium Halides Research Articles

Blue light emissive zero-dimensional hybrid cadmium bromide as fluorescence sensor toward benzaldehyde

Organic-inorganic hybrid low-dimensional metal halides have been widely studied as a new class of luminescence materials due to abundant structural diversity and intriguing photophysical property. Herein, we explored two new Cd-based 0D halides of [BHEPZ]CdBr4 (BHEPZ = 1,4-Bis(2-hydroxyethyl) piperazine) and [EPIPZ]CdBr4 (EPIPZ = 1-ethylpiperazine) through facile wet-chemistry method. These 0D halides exhibit blue light emissions derived from radiative recombination of self-trapped excitons (STEs) based on detailed spectroscopy investigations. More interestingly, [BHEPZ]CdBr4 exhibits rapid luminescence off switching toward benzaldehyde but fails in any other organic solvents. In-depth investigations demonstrate that the detection limit can fall to 2.65 ppm indicating perfect real-time fluorescent probe to detect benzaldehyde with high sensitivity and selectivity. This work enriches the cadmium halide materials and provide a new perspective for potential applications of 0D hybrid metal halides.

Multisite Fine-Tuning in Hybrid Cadmium Halides Enables Wide Range Emissions for Anti-Counterfeiting.

Achieving tunable emissions spanning the spectrum, from blue to near-infrared (NIR) light, within a single component is a formidable challenge with significant implication, particularly in tailoring multicolor luminescence for anti-counterfeiting purposes. In this study, we demonstrate a broad spectrum of emissions, covering blue to red and extending into NIR light in [BPy]2CdX4 : xSb3+ (BPy=Butylpyridinium; X=Cl, Br; x=0 to 0.08) through precise multisite structural fine-tuning. Notably, the multicolor emissions from [BPy]2CdBr4 : Sb3+ manifest a distinctive pattern, transitioning from blue to yellow in tandem with the host [BPy]2CdBr4 and further extending from yellow to NIR with its homologous [BPy]2CdCl4 : Sb3+, resulting in the simultaneous presence of intersecting and independent emission colors. Detailed modulation of chemical composition enables partial luminescence switching, facilitating the creation of diverse patterns with multicolor luminescence by employing [BPy]2CdX4 : xSb3+ as phosphors. This study for the first time successfully implements several groups of tunable emission colors in a single matrix via multisite fine-tuning. Such an effective strategy not only develops the specific relationships between tunable emissions and adjustable compositions, but also introduces a cost-effective and straightforward approach to achieving unique, high-level, plentiful-color and multiple-information-storage labels for advanced anti-counterfeiting applications.

Multisite Fine‐Tuning in Hybrid Cadmium Halides Enables Wide Range Emissions for Anti‐Counterfeiting

AbstractAchieving tunable emissions spanning the spectrum, from blue to near‐infrared (NIR) light, within a single component is a formidable challenge with significant implication, particularly in tailoring multicolor luminescence for anti‐counterfeiting purposes. In this study, we demonstrate a broad spectrum of emissions, covering blue to red and extending into NIR light in [BPy]2CdX4 : xSb3+ (BPy=Butylpyridinium; X=Cl, Br; x=0 to 0.08) through precise multisite structural fine‐tuning. Notably, the multicolor emissions from [BPy]2CdBr4 : Sb3+ manifest a distinctive pattern, transitioning from blue to yellow in tandem with the host [BPy]2CdBr4 and further extending from yellow to NIR with its homologous [BPy]2CdCl4 : Sb3+, resulting in the simultaneous presence of intersecting and independent emission colors. Detailed modulation of chemical composition enables partial luminescence switching, facilitating the creation of diverse patterns with multicolor luminescence by employing [BPy]2CdX4 : xSb3+ as phosphors. This study for the first time successfully implements several groups of tunable emission colors in a single matrix via multisite fine‐tuning. Such an effective strategy not only develops the specific relationships between tunable emissions and adjustable compositions, but also introduces a cost‐effective and straightforward approach to achieving unique, high‐level, plentiful‐color and multiple‐information‐storage labels for advanced anti‐counterfeiting applications.

Reactions of Cadmium(II) Halides and Di-2-Pyridyl Ketone Oxime: One-Dimensional Coordination Polymers.

The coordination chemistry of 2-pyridyl ketoximes continues to attract the interest of many inorganic chemistry groups around the world for a variety of reasons. Cadmium(II) complexes of such ligands have provided models of solvent extraction of this toxic metal ion from aqueous environments using 2-pyridyl ketoxime extractants. Di-2-pyridyl ketone oxime (dpkoxH) is a unique member of this family of ligands because its substituent on the oxime carbon bears another potential donor site, i.e., a second 2-pyridyl group. The goal of this study was to investigate the reactions of cadmium(II) halides and dpkoxH in order to assess the structural role (if any) of the halogeno ligand and compare the products with their zinc(II) analogs. The synthetic studies provided access to complexes {[CdCl2(dpkoxH)∙2H2O]}n (1∙2H2O), {[CdBr2(dpkoxH)]}n (2) and {[CdI2(dpkoxH)]}n (3) in 50-60% yields. The structures of the complexes were determined by single-crystal X-ray crystallography. The compounds consist of structurally similar 1D zigzag chains, but only 2 and 3 are strictly isomorphous. Neighboring CdII atoms are alternately doubly bridged by halogeno and dpkoxH ligands, the latter adopting the η1:η1:η1:μ (or 2.0111 using Harris notation) coordination mode. A terminal halogeno group completes distorted octahedral coordination at each metal ion, and the coordination sphere of the CdII atoms is {CdII(η1 - X)(μ - X)2(Npyridyl)2(Noxime)} (X = Cl, Br, I). The trans-donor-atom pairs in 1∙2H2O are Clterminal/Noxime and two Clbridging/Npyridyl; on the contrary, these donor-atom pairs are Xterminal/Npyridyl, Xbridging/Noxime, and Xbridging/Npyridyl (X = Br, I). There are intrachain H-bonding interactions in the structures. The packing of the chains in 1∙2H2O is achieved via π-π stacking interactions, while the 3D architecture of the isomorphous 2 and 3 is built via C-H∙∙∙Cg (Cg is the centroid of one pyridyl ring) and π-π overlaps. The molecular structures of 1∙2H2O and 2 are different compared with their [ZnX2(dpkoxH)] (X = Cl, Br) analogs. The polymeric compounds were characterized by IR and Raman spectroscopies in the solid state, and the data were interpreted in terms of the known molecular structures. The solid-state structures of the complexes are not retained in DMSO, as proven via NMR (1H, 13C, and 113Cd NMR) spectroscopy and molar conductivity data. The complexes completely release the coordinated dpkoxH molecule, and the dominant species in solution seem to be [Cd(DMSO)6]2+ in the case of the chloro and bromo complexes and [CdI2(DMSO)4].

Structure Prediction and Ultrasonic Assisted Synthesis of Coordination Compound Cadmium (II) Bromide with N,N’-diethylthiourea Ligand

Cadmium (II) halides with N,N'-diethylthiourea (detu) ligands at a stoichiometry of 1: 2 tend to form molecular complexes [Cd(detu)2X2] with a distorted tetrahedral geometry at the central atom. Generally, these complex compounds are prepared by the conventional method of reflux for 4 hour. The use of ultrasonic waves for complex synthesis can be an alternative to make the reaction time more efficient and environmentally friendly. The aim of this study was to synthesize and characterize complex compounds from CdBr2 and detu ligands using the ultrasonication method that have not previously reported. The synthesis of complex compounds was carried out by reacting CdBr2 and detu (1:2) in methanol solvent. In the synthesized compounds, a melting point test, electrical conductivity test, Fourier Transform Infrared (FTIR), Scanning Electron Microscope-Energy Dispersive Xray (SEM-EDX), qualitative test of bromide ion and calculation of free energy using Spartan'14 software were carried out for the complex structure prediction. The complex compound resulted has colorless needle crystals with a melting point of 93-94°C. The results of the EDX analysis provide the empirical formula C10H24CdBr2N4S2. The electrical conductivity test data and the bromide ion qualitative test proved that the synthesized complex compound was a molecular complex compound with the molecular formula [Cd(detu)2Br2]. The complex compound has two possible structures, namely a distorted tetrahedral and a square planar. Free energy calculations showed that complex compounds with a distorted tetrahedral structure and a square planar have free energies of -527.5574 kJ/mol and -408.7424 kJ/mol, respectively.

Ultralong Room‐Temperature Phosphorescence from Organic–Inorganic Hybrid Perovskitoid Based on Metal‐Organic Complex Component

AbstractOrganic–inorganic hybrid perovskite or perovskitoid phosphorescent materials have aroused extensive research interests due to their applications in organic light emitting diodes, anti‐counterfeiting, display, and other fields. Herein, a new strategy is proposed, employing metal‐organic complex (MOC) cations as the organic components, which can increase the spin–orbit coupling (SOC) and intersystem crossing (ISC) efficiencies of the organic units, and hybrid with inorganic parts to form a novel type MOC–inorganic composed perovskitoid. In detail, a lead‐free MOC–inorganic perovskitoid material, named P‐Cl, is synthesized by self‐assembly of preassembled MOC from metallized crown ethers with inorganic cadmium halide component. In the solid state, the assembled perovskitoid exhibits a tunable fluorescence color from blue to green, during which a cold white light emission is achieved. Interestingly, after removal of the radiation source, the perovskitoid still emits a bright and color‐tunable long persistent luminescence (LPL) from cyan to green. Single‐crystal X‐ray diffraction analysis and theoretical calculations reveal that the bright LPL of P‐Cl arises from the improvement of the metal‐organic part to increase the SOC and the interlocking of metal halogenated layers to inhibit the nonradiative transition. The proposed strategy not only broadens the range of organic–inorganic perovskitoid hybrid materials but also facilitates the design of multifunctional LPL materials.

High open-circuit voltage in lead sulfide quantum dot solar cells via solution-phase ligand exchange with low electron affinity cadmium halides

A solution-phase ligand exchange strategy is developed for cadmium halide ligands to passivate PbS quantum dots. The cadmium halide passivation curtails bandtail and trap states to achieve a record 0.7 V open circuit voltage in solar cells.

High-Efficiency Carbon-based CsPbI2 Br Perovskite Solar Cells from Dual Direction Thermal Diffusion Treatment with Cadmium Halides.

In recent years, carbon-based CsPbI2 Br perovskite solar cells (PSCs) have attracted more attention due to their low cost and good stability. However, the power conversion efficiency (PCE) of carbon-based CsPbI2 Br PSCs is still no more than 16%, because of the defects in CsPbI2 Br or at the interface with the electron transport layer (ETL), as well as the energy level mismatch, which lead to the loss of energy, thus limiting PCE values. Herein, a series of cadmium halides are introduced, including CdCl2 , CdBr2 and CdI2 for dual direction thermal diffusion treatment. Some Cd2+ ions thermally diffuse downward to passivate the defects inside or on the surface of SnO2 ETL. Meanwhile, the energy level structure of SnO2 ETL is adjusted, which is in favor of the transfer of electron carriers and blocking holes. On the other hand, part of Cd2+ and Cl- ions thermally diffuse upward into the CsPbI2 Br lattice to passivate crystal defects. Through dual direction thermal diffusion treatment by CdCl2 , CdI2 and CdBr2 , the performance of devices has been significantly improved, and their PCE has been increased from 13.01% of the original device to 14.47%, 14.31%, and 13.46%, respectively. According to existing reports, 14.47% is one of the highest PCE of carbon-based CsPbI2 Br PSCs with SnO2 ETLs.

A synergetic model for implementing single-component white-light emission: a case study of zero-dimensional cadmium halides

A serial of 0D (C6H7NX)2CdX4 (X = Cl, Br, I) are developed, and the synergetic controlling of π-conjugated ligands and [CdX4] units enables single-component ultra-broadband white-light emissions of (C6H7NCl)2CdCl4 and (C6H7NBr)2CdBr4.

An organic-inorganic hybrid cadmium chloride with face-sharing CdCl6 octahedral chains: Synthesis, crystal structure, optical and conduction mechanisms: [NH2(CH3)2]5Cd3Cl11

Organic-inorganic cadmium halides have recently emerged as promising alternatives to conventional optoelectronic materials thanks to their fascinating physical properties. The hybrid organic-inorganic compound Penta-dimethylammonium-Undecachlorotricadmate (II) [(CH3)2NH2]5Cd3Cl11, denoted DMAPCC, was synthesized at room temperature and its optical and electrical properties were studied. The structure shows the orthorhombic system with the Cmcm space group. The Raman spectroscopy, at room temperature, confirmed the presence of organic and inorganic sub-lattices. The UV–visible confirms the disorder of the structure and the semiconducting behavior of this compound. Furthermore, the electrical measurement confirms the thermal analysis result. Indeed, the variation of exponent s indicates the overlapping small polaron tunneling (NSPT) conduction model described the two phases of this material.Keys-words: hybrid materials, Optical properties, thermal properties, electrical properties and conduction mechanism.

Green Triplet Self-Trapped Exciton Emission in Layered Rb3Cd2Cl7:Sb3+ Perovskite: Comparison with RbCdCl3:Sb3.

Metal halide materials have recently sparked intense research because of their excellent photophysical properties and chemical stability. For example, RbCdCl3:Sb3+ exhibits broad emission at about 600 nm with a high photoluminescence quantum yield (PLQY) over 91% and double emission bands with bright white color. Herein, we obtained a novel Rb and Cd layered perovskite Rb3Cd2Cl7 doped with Sb3+, which gives luminescence at 525 nm with a large Stokes shift of 200 nm, originating from a self-trapped exciton (STE). Its PLQY is 57.47%, but its low-temperature PLQY becomes much higher at the same wavelength. When Rb3Cd2Cl7:Sb3+ and RbCdCl3:Sb3+ were compared, the two classes of quantum confinement effects by Rb and Cd ions in the lattice were identified to describe their electronic states and different optical properties. These results suggest that properties of Sb-doped cadmium halides could be modified by the structure type and local atomic confinement to find applications as promising luminescent materials for optoelectronic devices.

All-Inorganic Luminescent Ternary Cadmium Halide Cs7Cd3Br13 with Two Types of Cd-Centered Polyhedrons.

All-inorganic metal halides comprise a class of semiconductor material with a wide range of applications. In these materials, cadmium-related materials have excellent optical properties in the field of binary quantum dots. However, ternary cadmium halides have not attracted much attention until now. Here, we successfully synthesize a ternary all-inorganic cesium cadmium bromide, Cs7Cd3Br13, and obtained its acicular single crystals through a simple solvent evaporation method. Cadmium atoms are found to be coordinated with bromine atoms in two different polyhedrons including isolated [CdBr4]2- tetrahedrons and corner-shared [CdBr6]4- octahedral chains in the unit cells of Cs7Cd3Br13. Optical properties are then measured and the needlelike single crystals are found to have an orange emission at 630 nm upon 365 nm UV light with a photoluminescence quantum yield (PLQY) of 9.85%. The orange luminescence with large Stokes shift (255 nm) and broad full width at half-maximum (fwhm = 147 nm) is derived from self-trapped excitons, and it is further evidenced by temperature-variable photoluminescence spectra. The PL decay spectrum shows the lifetime of Cs7Cd3Br13 is 1.26 μs. Finally, DFT calculation reveals that Cs7Cd3Br13 has a direct band gap with a value of 3.09 eV.

Crystal rigidifying strategy toward hybrid cadmium halide to achieve highly efficient and narrowband blue light emission

Highly efficient and narrowband blue light-emitting performance is extremely crucial for the optoelectronic applications of organic-inorganic hybrid perovskites. However, the not yet viable approach has been shown to simultaneously improve photoluminescence quantum yield (PLQY) and narrow linewidth of blue light emission. Herein, a new crystal rigidifying strategy is proposed as a viable dual-optimization avenue. Specifically, we perform a post-synthetic technique on hybrid cadmium halides and successfully convert zero-dimensional (0D) DMP-0-CdBr4 to one-dimensional (1D) DMP-1-CdBr3, accompanied by luminescent transformation from sky-blue (470 nm) to deep-blue (432 nm) emissions. The structural evolution from discrete block to infinite chain significantly enhances the crystal rigidity, which results in narrower emission linewidth (89 to 50 nm) and increased color purity (74.5% to 96.7%). Synchronously, the PLQY also realizes a notable enhancement from 14.0% to 52.3%. Systematical characterizations demonstrate that enhanced crystal rigidity simultaneously weakens the electron-phonon interaction and slows down nonradiative decay, which narrows the emission linewidth and boosts the PLQY. The highly efficient light-emitting performance enables them as excellent down-conversion blue phosphors to fabricate solid-state LED giving bright warm white light with high color rendering index of 95.4. This work paves a novel structural optimization way to rationally design or fine-tune high-performance blue-light emitting halides.

Hard-Soft Interactions in Solvent Extraction with Basic Extractants: Comparing Zinc and Cadmium Halides.

Solvent extraction is often applied to separate and purify metals on an industrial scale. Nevertheless, solvent extraction processes are challenging to develop because of the complex chemistry involved. For basic extractants, much of the chemical behavior remains poorly understood due to the conditions far from thermodynamic ideality. To elucidate the extraction mechanism, we studied the speciation and extraction of zinc(II) and cadmium(II) from chloride, bromide, and iodide media by using a basic extractant consisting of a trioctylmethylammonium cation and, respectively, a chloride, bromide, or iodide anion. These systems were specifically selected to increase the understanding of the less-studied bromide and iodide media and to focus on the effect of hard–soft interactions on solvent extraction systems. It was observed that, in general, a metal is more efficiently extracted when its hydration in the aqueous phase is lower and its stabilization in the organic phase is higher. In the investigated systems, these conditions are obtained by forming metal complexes with a lower charge density by coordinating the right number of halide anions and by selecting a halide with a lower charge density. In the organic phase, the stability of the metal complex can be increased by forming strong metal–anion bonds and by decreasing the water content. These insights might be of interest in the development and optimization of separation schemes for metals.

Synthesis, crystal structures, and luminescence properties of coordination polymers and a discrete complex of cadmium(ii) halides with 1-(1,2,4-triazol-1-yl)adamantane

Synthesis, crystal structures, and luminescence properties of coordination polymers and a discrete complex of cadmium(ii) halides with 1-(1,2,4-triazol-1-yl)adamantane

Zinc and Cadmium Complexes of Chelating N-Heterocyclic Silylene and Their Reactivity toward Elemental Chalcogens

The reactions of the pyridine-functionalized silylene LNSi [L = PhC(NtBu)2; N = 2-(methylamido)pyridine] with zinc and cadmium halides are described. These resulted in the formation of a series of zinc and cadmium silylene complexes: [LNSi-ZnX2] (X = Cl, Br, I) and [{LNSi-CdI2}2], which is the first cadmium silylene compound. Subsequent reaction of these silylene complexes with elemental sulfur and selenium under mild conditions at room temperature afforded under activation of these elements the corresponding silanethione-stabilized zinc [(LNSi═S)-ZnX2] (X = Cl, I) and cadmium [(LNSi═S)-CdI2] complexes and the silaneselenone-stabilized zinc species [(LNSi═Se)-ZnCl2]. A selective insertion of the group 16 elements into the M-Si bond of the silylenes was observed. Because of metal coordination, the Si-chalcogen bond lengths in the silanethiones and silaneselenones are enlarged and thus range between a single and a double bond. All new compounds were fully characterized by single-crystal X-ray diffraction analyses, multinuclear NMR spectroscopy, elemental analyses, and IR spectroscopy.

Cadmium halide coordination complexes of serpentine pentadentate ligands

A series of morphologically distinct cadmium halide complexes were obtained from potentially pentadentate, serpentine ligands 2,6-bis([(2-pyridylmethyl)oxy]methyl)-pyridine (L) and 2,6-bis([(2-pyridylmethyl)thio]methyl)pyridine (L*). Methods were developed to isolate crystalline materials ranging from mononuclear [CdLCl2] (1) to zig-zag one-dimensional polymer {[CdL(μ-Cl)]2(CdCl4)}n·n(CH3CN) (2) for L and from one-dimensional helical polymers [CdL*Cl2]n (3) and [CdL*Br2]n (4) to dinuclear [CdL*(μ-Br)(CdBr3)]2 (toluene solvate 5a, ether solvate 5b) or three-dimensional polymer [((Cd(μ-Cl)2)2L*)2]n (6) for L*. Compounds 1 and 2 had pentagonal bipyramidal metal centers with L in a pseudo-planar spiral, pentadentate mode. In contrast, the complexes of L* had octahedral metal centers with a bis-N,S metal-bridging ligand binding mode linking Cd(halogen)2 units in polymeric complexes 3, 4, and 6, but a pentadentate Λ2/Δ2 ligand conformation in dinuclear complexes 5a and 5b. Interactions involved in supramolecular aggregation included offset π-π stacking interactions and edge-to-face σ-π interactions, as well as anion-π(pyridine) interactions, chalcogen–chalcogen interactions, halogen-chalcogen interactions and CH⋯X–Cd halide hydrogen bonds. Additional characterizations of the complexes included elemental analysis, solution 1H NMR spectroscopy, FTIR, TGA and PXRD.

Multi‐Mode Color‐Tunable Long Persistent Luminescence in Single‐Component Coordination Polymers

AbstractMaterials with tunable long persistent luminescence (LPL) properties have wide applications in security signs, anti‐counterfeiting, data encrypting, and other fields. However, the majority of reported tunable LPL materials are pure organic molecules or polymers. Herein, a series of metal‐organic coordination polymers displaying color‐tunable LPL were synthesized by the self‐assembly of HTzPTpy ligand with different cadmium halides (X=Cl, Br, and I). In the solid state, their LPL emission colors can be tuned by the time‐evolution, as well as excitation and temperature variation, realizing multi‐mode dynamic color tuning from green to yellow or green to red, and are the first such examples in single‐component coordination polymer materials. Single‐crystal X‐ray diffraction analysis and theoretical calculations reveal that the modification of LPL is due to the balanced action from single molecule and aggregate triplet excited states caused by an external heavy‐atom effect. The results show that the rational introduction of different halide anions into coordination polymers can realize multi‐color LPL.

Multi-Mode Color-Tunable Long Persistent Luminescence in Single-Component Coordination Polymers.

Materials with tunable long persistent luminescence (LPL) properties have wide applications in security signs, anti-counterfeiting, data encrypting, and other fields. However, the majority of reported tunable LPL materials are pure organic molecules or polymers. Herein, a series of metal-organic coordination polymers displaying color-tunable LPL were synthesized by the self-assembly of HTzPTpy ligand with different cadmium halides (X=Cl, Br, and I). In the solid state, their LPL emission colors can be tuned by the time-evolution, as well as excitation and temperature variation, realizing multi-mode dynamic color tuning from green to yellow or green to red, and are the first such examples in single-component coordination polymer materials. Single-crystal X-ray diffraction analysis and theoretical calculations reveal that the modification of LPL is due to the balanced action from single molecule and aggregate triplet excited states caused by an external heavy-atom effect. The results show that the rational introduction of different halide anions into coordination polymers can realize multi-color LPL.

Coordination of a (Npy)2NimineNamine-Donor Oxazolidine Ligand Toward CdX2 (X = Cl, Br, I) with 1:1 and 2:1 M:L Molar Ratios Along with Spectral, Theoretical, and Structural Studies

A series of reactions between an oxazolidine ligand 2-(2-(pyridin-2-yl)oxazolidin-3-yl)-N-(pyridin-2-ylmethylene)ethanamine (POPME) and CdX2 (X = Cl, Br, I) salts with different M:L molar ratios (1:1 and 2:1) is experimentally studied to determine the most stable product of these reactions. All products are characterized by the elemental analysis, FTIR, Raman, and 1H NMR spectroscopy, and single crystal X-ray diffraction. Examinations reveal that only one product is formed from 1:1 and 2:1 M:L reactions between each cadmium(II) halide with POPME. The thermodynamic stability and charge distribution patterns of the compound containing bromide are analyzed by DFT and NBO.