Two-dimensional Cadmium Research Articles

Data acquisition system for a newly-built hard x-ray/soft gamma-ray spectrometer imaging system on experimental advanced superconducting tokamak

A portable hard X-ray and soft gamma-ray spectrometer imaging system (HXS) has been constructed to gather physical information about fast electrons confined in the Experimental Advanced Superconducting Tokamak (EAST). The system is installed on the low field side of the mid-plane and provides a viewing field tangential to the toroidal field. The system utilizes a two-dimensional Cadmium Zinc Telluride (CdZnTe) semiconductor detector with 128 channels, and a data acquisition (DAQ) system has been designed for it. The DAQ system features a highly integrated signal processing system with the capability of high-speed processing and digital transmission of signals from 128 channels. In addition, a related DAQ software has been developed using a modular design approach, facilitating tasks such as data reception, storage, and preliminary processing. HXS, which has been applied during the recent EAST campaign, directly obtains the digital energy spectrum of incident photons. The DAQ system is described in detail in this paper. The hardware components and energy calibration have also been described. Experimental data have been successfully obtained and briefly discussed. More physical research will be reported in future publications.

Amplified Spontaneous Emission from Electron-Hole Quantum Droplets in Colloidal CdSe Nanoplatelets.

Two-dimensional cadmium selenide nanoplatelets (NPLs) exhibit large absorption cross sections and homogeneously broadened band-edge transitions that offer utility in wide-ranging optoelectronic applications. Here, we examine the temperature-dependence of amplified spontaneous emission (ASE) in 4- and 5-monolayer thick NPLs and show that the threshold for close-packed (neat) films decreases with decreasing temperature by a factor of 2-10 relative to ambient temperature owing to extrinsic (trapping) and intrinsic (phonon-derived line width) factors. Interestingly, for pump intensities that exceed the ASE threshold, we find development of intense emission to lower energy in particular provided that the film temperature is ≤200 K. For NPLs diluted in an inert polymer, both biexcitonic ASE and low-energy emission are suppressed, suggesting that described neat-film observables rely upon high chromophore density and rapid, collective processes. Transient emission spectra reveal ultrafast red-shifting with the time of the lower energy emission. Taken together, these findings indicate a previously unreported process of amplified stimulated emission from polyexciton states that is consistent with quantum droplets and constitutes a form of exciton condensate. For studied samples, quantum droplets form provided that roughly 17 meV or less of thermal energy is available, which we hypothesize relates to polyexciton binding energy. Polyexciton ASE can produce pump-fluence-tunable red-shifted ASE even 120 meV lower in energy than biexciton ASE. Our findings convey the importance of biexciton and polyexciton populations in nanoplatelets and show that quantum droplets can exhibit light amplification at significantly lower photon energies than biexcitonic ASE.

Topological control through the solvent effect in two-dimensional cadmium coordination polymers

Two new solvent-induced cadmium (II) coordination polymers, {[CdL1.5(NO3)2](CH3CN)}n (1) and [CdL(NO3)2(H2O)]n (2) were successfully synthesized from the same initial materials Cd(NO3)2.4H2O and 1,4-bis(3-pyridyl)-2,3-diaza-1,3-butadiene (L) in EtOH/CH3CN and CH3CN solvent systems, respectively. These coordination polymers were structurally characterized by single-crystal X-ray diffraction analysis and further identified by infrared spectra (FTIR) and powder X-ray diffraction (PXRD). The influence of the solvent system can be observed by a significant change in the topological features. As controlled by solvent, compound 1 shows a 2D coordination polymer that can be simplified as a (6,3) net, while compound 2 is two-dimensional (4,4) coordination network. Our results provide interesting insights into solvent effects on the topological control in construction of non-interpenetrated coordination polymers. Hirshfeld surface analysis of the structures 1 and 2 is used to investigate the percentage of participation of intermolecular interactions in the crystal packing of compounds 1 and 2.

Flexible Memristor Constructed by 2D Cadmium Phosphorus Trichalcogenide for Artificial Synapse and Logic Operation (Adv. Funct. Mater. 9/2023)

Transition-Metal Phosphorus Trichalcogenide In article number 2211269, Jiahong Wang, Cong Ye, and co-workers report a flexible memristor fabricated utilizing two-dimensional cadmium phosphorus trichalcogenide nanosheets; the synaptic plasticity, including paired-pulse facilitation and spiking timing-dependent plasticity, are further observed. Owing to the linear conductance modulation capacity, the decimal operation is explored.

Dual imaging modality of fluorescence and transmission X-rays for gold nanoparticle-injected living mice.

X-ray fluorescence (XRF) imaging for metal nanoparticles (MNPs) is a promising molecular imaging modality that can determine dynamic biodistributions of MNPs. However, it has the limitation that it only provides functional information. In this study, we aim to show the feasibility of acquiring functional and anatomic information on the same platform by demonstrating a dual imaging modality of pinhole XRF and computed tomography (CT) for gold nanoparticle (GNP)-injected living mice. By installing a transmission CT detector in an existing pinhole XRF imaging system using a two-dimensional (2D) cadmium zinc telluride (CZT) gamma camera, XRF and CT images were acquired on the same platform. Due to the optimal X-ray spectra for XRF and CT image acquisition being different, XRF and CT imaging were performed by 140 and 50kV X-rays, respectively. An amount of 40mg GNPs (1.9nm in diameter) suspended in 0.20ml of phosphate-buffered saline were injected into the three BALB/c mice via a tail vein. Then, the kidney and tumor slices of mice were scanned at specific time points within 60min to acquire time-lapse in vivo biodistributions of GNPs. XRF images were directly acquired without image reconstruction using a pinhole collimator and a 2D CZT gamma camera. Subsequently, CT images were acquired by performing CT scans. In order to confirm the validity of the functional information provided by the XRF image, the CT image was fused with the XRF image. After the XRF and CT scan, the mice were euthanized, and major organs (kidneys, tumor, liver, and spleen) were extracted. The ex vivo GNP concentrations of the extracted organs were measured by inductively coupled plasma mass spectrometry (ICP-MS) and L-shell XRF detection system using a silicon drift detector, then compared with the in vivo GNP concentrations measured by the pinhole XRF imaging system. Time-lapse XRF images were directly acquired without rotation and translation of imaging objects within an acquisition time of 2min per slice. Due to the short image acquisition time, the time-lapse in vivo biodistribution of GNPs was acquired in the organs of the mice. CT images were fused with the XRF images and successfully confirmed the validity of the XRF images. The difference in ex vivo GNP concentrations measured by the L-shell XRF detection system and ICP-MS was 0.0005-0.02% by the weight of gold (wt%). Notably, the in vivo and ex vivo GNP concentrations in the kidneys of three mice were comparable with a difference of 0.01-0.08wt%. A dual imaging modality of pinhole XRF and CT imaging system and L-shell XRF detection system were successfully developed. The developed systems are a promising modality for in vivo imaging and ex vivo quantification for preclinical studies using MNPs. In addition, we discussed further improvements for the routine preclinical applications of the systems.

A new two-dimensional cadmium(II) coordination polymer based on the asymmetric dicarboxylic acid homophthalic acid: synthesis, structure and properties.

A new coordination polymer poly[[μ2-4,4'-bis(2-methylimidazol-1-yl)biphenyl-κ2N3:N3']bis[μ3-2-(2-carboxylatophenyl)acetato-κ5O,O':O',O'':O'']dicadmium(II)], [Cd(C9H6O4)(C20H18N4)0.5]n or [Cd(HMPH)(4,4'-BMIBP)0.5]n [H2HMPH is homophthalic acid and 4,4'-BMIBP is 4,4'-bis(2-methylimidazol-1-yl)biphenyl], (I), was synthesized by the solvothermal method and was structurally characterized by means of single-crystal X-ray diffraction, IR spectroscopy and elemental analysis. Coordination polymer (I) exhibits a two-dimensional layer based on one-dimensional [Cd(HMPH)]n chains. Remarkably, photocatalytic degradation experiments on methylene blue (MB) indicated that (I) exhibits an obvious degradation effect. Moreover, an investigation of the luminescence properties of (I) revealed that it could be considered as a potential highly selective luminescence sensor for nitrofurantoin (NFT).

Insight into the High Proton Conductivity of One-/Two-Dimensional Cadmium Phosphites.

The study describes the synthesis and structural attributes of two new cadmium phosphites, [Cd{OP(O)(OH)H}2(4,4'-bipy)] (1) and [H2pip][Cd(HPO3)2(H2O)]·H2O (2). The structure of 1 adopts a two-dimensional motif featuring alternate [Cd-μ2-O]2 and [Cd-O-P-O]2-cyclic rings, while the inorganic chains are held together by 4,4'-bipyridine. The presence of strong hydrogen bonding interactions between the appended H2PO3 groups (O---O = 2.55 Å) provides a facile proton conduction pathway and results in a proton conductivity of 3.2 × 10-3 S cm-1 at 75 °C under 77% relative humidity (RH). Compound 2 comprises an anionic framework formed by vertex-shared [Cd-O-P-O]2-cyclic rings, while the [H2pip] cations between the adjacent chains assist a well-directed O-H---O hydrogen-bonded network between coordinated water, lattice water, and phospite groups. The bulk proton conductivity value under conditions as in 1 reaches 4.3 × 10-1 S cm-1. For both 1 and 2, the proton conductivity remains practically unchanged under ambient temperatures (25-35 °C), suggesting their potential in low-temperature fuel cells.

A new two-dimensional cadmium(II) coordination polymer based on Cd6(CHADC)6 clusters (H2CHADC is cyclohexane-1,2-dicarboxylic acid): synthesis, structure and properties.

The highly effective recognition and detection of metal ions and anions in water has attracted much attention with respect to environmental safety. Herein, a novel Cd-based coordination polymer, poly[[4,4'-bis(2-methylimidazol-1-yl)biphenyl]bis(cyclohexane-1,2-dicarboxylato)dicadmium(II)], [Cd2(C8H10O4)2(C20H18N4)]n or [Cd(CHADC)(4,4'-BMIBP)0.5]n, (I), has been synthesized employing cis-cyclohexane-1,2-dicarboxylic acid (H2CHADC) and 4,4'-bis(2-methyl-1H-imidazol-1-yl)biphenyl (4,4'-BMIBP). Single-crystal X-ray analysis reveals that (I) presents a 6-connected hxl two-dimensional layer based on Cd6(CHADC)6 clusters with the point symbol (36·46·53). Furthermore, (I) has been characterized by elemental analysis, IR spectroscopy, thermogravimetric analysis and fluorescence spectroscopy, and exhibits good stability and excellent photoluminescence properties. Coordination polymer (I) was chosen as a fluorescent probe to sense different target analytes and shows an obvious selective recognition response to Fe3+ cations and Cr2O72-/CrO42- anions through luminescence-quenching effects in aqueous solution. The sensing mechanism was investigated and showed that the detection mechanism was resonance energy transfer between (I) and the Fe3+, Cr2O72- and CrO42- ions.

A new two-dimensional homochiral cadmium(II) coordination polymer: synthesis, structure determination, optical properties, and fluorescent sensing

A new two-dimensional (2D) homochiral cadmium(II) coordination polymer, {[Cd4(OH)2(L)2(pea)4]·CH3OH} n (1) (pea = (S)-1-phenylethanamine), was solvothermally synthesized based on an enantiomerically pure chiral ligand (S)-5-(((1-carboxy-2-phenylethyl)amino) methyl)isophthalic acid (H3L). Crystal structure analysis shows that 1 is a 2D homochiral framework consisting of coaxial double-helical chains where a pair of left- and right-handed 21 helixes shares tetranuclear Cd cluster subunits [Cd4(μ 3-OH)2]. Topologically, 1 is an interesting 3,6-connected network with the point symbol of (43)2(46·66·83). The thermal stability and solid-state optical properties, including circular dichroism, and nonlinear optical and luminescent properties of 1 were systematically investigated. Furthermore, the fluorescence response of 1 to various common solvents and metal ions was preliminarily studied. Interesting enough, N,N-dimethylformamide (DMF), N,N-dimethylacetamide (DMA), acetone and Fe3+ ion have strong quenching effect on the fluorescence of 1, indicating that 1 has certain potential application in the visual detection of these species.

Hydrothermal synthesis of two-dimensional cadmium(II) micro-porous coordination material based on Bi-functional building block and its application in highly sensitive detection of Fe3+ and Cr2O72−

Metal-organic framework (MOFs), also known as porous coordination polymers (PCPs), is a new kind of crystalline porous materials, which has received extensive attention in the past few decades. As a new type of sensing material, MOFs stand out from many other traditional fluorescence sensors because of its crystal characteristics, structural diversity, stable porosity and adjustable functional characteristics. In this work, the bi-functional building block containing aromatic carboxylic acid and triazole moieties, namely 3-(1H-1,3,4-triazol-1-yl) benzoic acid, was selected as the linker to synthesize {[Cd(µ5-L)⋅I}n (1, HL = 3-(1H-1,3,4-triazol-1-yl)benzoic acid) by hydrothermal method with transition CdII metal centers. Firstly, the preliminary characterization of 1 was carried out by means of PXRD, FT-IR, and then the UV and fluorescence tests were conducted to study the fluorescence properties of 1. The crystal structure analysis indicates that CdII is the center and the ligand is bridged to form a two-dimensional porous structure. In addition, 1 has good selectivity for Fe3+ and Cr2O72−, meanwhile, it has high detection sensitivity (Ksv quenching efficiency for Fe3+: 1.2 × 104 M−1 and Cr2O72− 1.85 × 104 M−1) and low detection limit (Fe3+: 19.21 μM and Cr2O72−: 12.46 μM). The results of photoluminescence test show that 1 can detect cations and anions with high sensitivity, resist the interference of other ions, and have good reusability. As far as we know, 1 is the first example of ultra-stable two-dimensional (2D) Cadmium (II) microporous coordination material as a fluorescence sensor for Fe3+ and Cr2O72−.

Aliphatic amine mediated assembly of [M6(mna)6] (M = Cu/Ag) into extended two-dimensional structures: synthesis, structure and Lewis acid catalytic studies

New aliphatic amine directed two-dimensional cadmium coordination polymers were shown to exhibit Lewis-acid catalytic activity for the cyanation of imines.

Electronic Band Structure and Ultrafast Carrier Dynamics of Two Dimensional (2D) Semiconductor Nanoplatelets (NPLs) in the Presence of Electron Acceptor for Optoelectronic Applications

Two-dimensional (2D) cadmium chalcogenide nanoplatelets (NPLs) have been grown as an emerging material for optoelectronic applications because of their unique properties. Here, we investigate the c...

2D Cadmium Chalcogenides for Optoelectronics

Two-dimensional(2D) cadmium chalcogenides have triggered worldwide interests due to their unique merits in both structure and physical properties, including thickness-dependent bandgaps, narrow emission line widths, high intrinsic absorption coefficient and large absorption cross sections, etc., rendering their great potential for next-generation electronics and optoelectronics devices. In this article, the progress of 2D cadmium chalcogenides in the past few years is comprehensively reviewed. We first discussed several synthetic strategies for various 2D cadmium chalcogenides. Then, their optoelectronic applications in photodetectors, lasers, LEDs, and piezoelectric devices are summarized and commented in detail. Finally, a brief conclusion of the article and the future prospects of the 2D cadmium chalcogenides are provided.

A multi-responsive regenerable water-stable two-dimensional cadmium (II) fluorescent probe for highly selective, sensitive and real-time sensing of nitrofurazone and cupric ion

In recent years, luminescent metal organic frameworks (MOFs) materials have attracted widespread attention in the field of fluorescence sensing. In this work, a novel two-dimensional (2D) micro-porous water-stable coordination material {[Cd(μ3-HL)2(H2O)]⋅2.3H2O}n (1, H2L = 4,4′-(1H-1,2,4-triazol-1-yl)methylene-bis (benzonic acid)) has been prepared through the powerful solvo-thermal approaches, which has been characterized by single crystal X-ray diffraction analysis, PXRD, scanning electron microscope (SEM) and Transmission electron microscopy (TEM) characterization. Crystal structural analysis also reveals the partly de-pronated μ3-coordinated HL− adopted tri-dentate bridging mode, which link these cadmium (II) centers, eventually forming the two-dimensional (2D) micro-porous coordination framework of 1. 1D channel with diemsionality of 12.216(3) Å × 8.578(11) Å that can be observed along the crystallographic a axis. It is noted that 1 has good chemical stability and maintains structural integrity not only in various solvents, but also in aqueous solutions with pH values varying from 2 to 12. Additionally, 1 has the unique advantages such as high detection sensitivity for Nitrofurazone (NZF) and Cupric ion (Cu2+) (Ksv quenching efficiency for NZF: 5.0 × 106 M−1 and Cu2+ 5.6 × 106 M−1) and low detection limits (NZF: 1.21 μM and Cu2+: 1.07 μM), good selectivity and good real-time performance. The result of photo-luminescent experiment demonstrates that 1 can realize high sensitivity and real-time chemical discrimination of antibiotics and ions, and has good reusability. To the best of our knowledge, 1 is the first example of the ultra-stable 2D cadmium (II) micro-porous coordination material as a renewable chemical sensor for NZF and Cu2+.

Two-Dimensional Cadmium Hydroxide Nanosheets for Electrochemical Capacitors Under High Operating Voltage

Electrochemical capacitors are deemed to be the most prospective energy storage devices in the field of alternative energy sources. Here, cadmium hydroxide (Cd(OH)2) nanosheets are hydrothermally synthesized and used as electrodes for supercapacitors. Physiochemical properties of the as-synthesized materials are examined using powder x-ray diffraction, scanning electron microscopy, high-resolution transmission electron microscopy and energy-dispersive x-ray spectroscopy measurements. Electrochemical investigations reveal an excellent operating potential window of 1.5 V, with the specific capacitance of ∼ 71 F g−1 at a scan rate of 2 mV s−1. In addition, the Cd(OH)2 electrodes are complemented by good cyclic retention for 2000 cycles. Further, the analysis of the type of charge-storage mechanism reveals prominent contributions from the diffusion-controlled processes.

Atomically Thin Population of Colloidal CdSe Nanoplatelets: Growth of Rolled-up Nanosheets and Strong Circular Dichroism Induced by Ligand Exchange

Colloidal two-dimensional cadmium chalcogenides nanoplatelets have recently emerged as a class of semiconductor nanoparticles with the narrowest emission and absorption excitonic bands that are of interest for optical applications. Here, we have developed a synthesis protocol for 2.5-monolayer-(ML) thick CdSe nanosheets as a single population. We found that a two-step synthesis in the presence of water promoted the growth of atomically thin nanosheets with high structural and morphological perfection. Using a seeded-growth technique, we extended the lateral size of nanosheets up to 400 nm, which led to the formation of multiwall rolled-up nanostructures. Ligand exchange of native oleic acid, attached to Cd-rich (001) planes, with achiral thioglycolic acid and chiral N-acetylcysteine retains a scroll-like morphology of nanosheets, in contrast to a thicker 3.5 ML population. A reorientation from the [110] to [100] folding direction was found during the change from an achiral to a chiral ligand. In the case ...

Exciton Spatial Coherence and Optical Gain in Colloidal Two-Dimensional Cadmium Chalcogenide Nanoplatelets.

Two-dimensional (2D) cadmium chalcogenide (CdX, X = Se, S, Te) colloidal nanoplatelets (NPLs) make up an emerging class of quantum well materials that exhibit many unique properties including uniform quantum confinement, narrow thickness distribution, large exciton binding energy, giant oscillator strength, long Auger lifetime, and high photoluminescence quantum yield. These properties have led to their great performances in optoelectrical applications such as lasing materials with a low threshold and large gain coefficient. Many of these properties are determined by the structure and dynamics of band-edge excitons in these 2D materials. Motivated by fundamental understanding of both 2D nanomaterials and their applications, the properties of 2D excitons have received intense recent interest. This Account provides an overview of three key properties of 2D excitons: how big is the 2D exciton (i.e., exciton center-of-mass coherent area); how the exciton moves in 2D NPLs (i.e., exciton in-plane transport mechanism); how multiple excitons interact with each other (i.e., biexciton Auger recombination); and their effects on the optical gain mechanism and threshold of colloidal NPLs. After a brief introduction in Section 1, the current understandings of 2D electronic structures of cadmium chalcogenide NPLs, and type-I CdSe/CdS and type-II CdSe/CdTe core/crown NPL heterostructures are summarized in Section 2. Section 3 discusses the direct measurement of exciton center-of-mass coherent area in 2D CdSe NPLs, its dependence on NPL parameters (thickness, lateral area, dielectric environment, and temperature), and the resulting giant oscillator strength transition (GOST) effect in 2D NPLs. 2D exciton diffusive in-plane transport in CdX NPLs and the comparison of exciton transport mechanisms in 2D NPLs and 1D nanorods are reviewed in Section 4. How Auger recombination lifetime depends on nanocrystal dimensions in NPLs, quantum dots, and nanorods is discussed in Section 5. The lateral area and thickness dependent Auger recombination rates of NPLs are shown to be well described by a model that accounts for the different dependence of the Auger recombination rates on the quantum confined and nonconfined dimensions. It is shown that Auger recombination rates do not follow the "universal volume scaling" law in 1D and 2D nanocrystals. Section 6 describes optical gain mechanisms in CdSe NPLs and the dependence of optical gain threshold on NPL lateral size, optical density, and temperature. The differences of optical gain properties in 0D-2D and the bulk materials are also discussed, highlighting the unique gain properties of 2D NPLs. At last, the Account ends with a summary and perspective of key remaining challenges in this field in Section 7.

A new twofold interpenetrated two-dimensional cadmium(II) coordination polymer constructed from 2,2'-(benzene-1,4-dicarboxamido)dipropionate.

In recent years, much initial interest and enthusiasm has focused on the self-assembly of coordination polymers due to the aesthetics of their crystalline architectures and their potential applications as new functional materials. As part of an exploration of chiral coordination polymers, a new twofold interpenetrated two-dimensional (2D) coordination polymer, namely, poly[[tetraaquabis[μ3-(2R,2'R)-2,2'-(benzene-1,4-dicarboxamido)dipropionato-κ5O,O':O'',O''':O'']dicadmium(II)] trihydrate], {[Cd2(C14H14N2O6)2(H2O)4]·3H2O}n, has been synthesized by the reaction of Cd(CH3COO)2·2H2O with the designed ligand (2R,2'R)-2,2'-(benzene-1,4-dicarboxamido)dipropionic acid (H2L). The compound has been structurally characterized by elemental analysis, IR spectroscopy, powder X-ray diffraction and single-crystal X-ray diffraction analysis. In the crystal structure, each CdII cation binds to three carboxylate groups from two crystallographically independent L2- dianions. Four carboxylate groups link two crystallographically independent cadmium cations into a 4,4-connected secondary building unit (SBU). The resulting SBUs are extended into a two-dimensional folding sheet via the terephthalamide moiety of the ligand as a spacer, which can be simplified as a (4,4)-connected 4,4L15 net with the point symbol (3.53.62)(32.52.62). In the lattice, two independent folding sheets interpenetrate each other to yield a double-sheet layer. The resulting 2D layers pack in parallel arrays through intermolecular hydrogen bonds and interlayer π-π interactions. The thermal stability and photoluminescence properties of the title compound have been investigated and it exhibits an enhanced fluorescence emission and a longer lifetime compared with free H2L.

A two-dimensional cadmium(II) coordination polymer constructed from 4-carboxy-1-(4-carboxylatobenzyl)-2-propyl-1H-imidazole-5-carboxylate and 1-(4-carboxylatobenzyl)-2-propyl-1H-imidazole-4-carboxylate ligands.

Crystals of poly[[aqua[μ3-4-carboxy-1-(4-carboxylatobenzyl)-2-propyl-1H-imidazole-5-carboxylato-κ5O1O1':N3,O4:O5][μ4-1-(4-carboxylatobenzyl)-2-propyl-1H-imidazole-4-carboxylato-κ7N3,O4:O4,O4':O1,O1':O1]cadmium(II)] monohydrate], {[Cd2(C15H14N2O4)(C16H14N2O6)(H2O)]·H2O}n or {[Cd2(Hcpimda)(cpima)(H2O)]·H2O}n, (I), were obtained from 1-(4-carboxybenzyl)-2-propyl-1H-imidazole-4,5-dicarboxylic acid (H3cpimda) and cadmium(II) chloride under hydrothermal conditions. The structure indicates that in-situ decarboxylation of H3cpimda occurred during the synthesis process. The asymmetric unit consists of two Cd2+ centres, one 4-carboxy-1-(4-carboxylatobenzyl)-2-propyl-1H-imidazole-5-carboxylate (Hcpimda2-) anion, one 1-(4-carboxylatobenzyl)-2-propyl-1H-imidazole-4-carboxylate (cpima2-) anion, one coordinated water molecule and one lattice water molecule. One Cd2+ centre, i.e. Cd1, is hexacoordinated and displays a slightly distorted octahedral CdN2O4 geometry. The other Cd centre, i.e. Cd2, is coordinated by seven O atoms originating from one Hcpimda2- ligand and three cpima2- ligands. This Cd2+ centre can be described as having a distorted capped octahedral coordination geometry. Two carboxylate groups of the benzoate moieties of two cpima2- ligands bridge between Cd2 centres to generate [Cd2O2] units, which are further linked by two cpima2- ligands to produce one-dimensional (1D) infinite chains based around large 26-membered rings. Meanwhile, adjacent Cd1 centres are linked by Hcpimda2- ligands to generate 1D zigzag chains. The two types of chains are linked through a μ2-η2 bidentate bridging mode from an O atom of an imidazole carboxylate unit of cpima2- to give a two-dimensional (2D) coordination polymer. The simplified 2D net structure can be described as a 3,6-coordinated net which has a (43)2(46.66.83) topology. Furthermore, the FT-IR spectroscopic properties, photoluminescence properties, powder X-ray diffraction (PXRD) pattern and thermogravimetric behaviour of the polymer have been investigated.

Temperature-dependent studies of a new two-dimensional cadmium dicyanamide framework exhibiting an unusual temperature-induced irreversible phase transition into a three-dimensional perovskite-like framework

We report the synthesis, crystal structure, and thermal, dielectric, optical and phonon properties of a new two-dimensional (2D) cadmium(ii) complex [(C3H7)4N][Cd(N(CN)2)3]. Our results show that this compound crystallizes in a two-dimensional monoclinic structure, with the space group P2/n, with ordered tetrapropylammonium cations and disorder of some dicyanamide linkers. It undergoes a structural phase transition at 245 K into another low-temperature (LT) monoclinic structure, with the space group P21/n. X-ray diffraction, dielectric, IR and Raman studies show that freezing of the dca motions stands at the origin of the phase transition. Optical studies indicate that this material has an energy band gap of 4.83 eV and exhibits intense bluish-white emission under 266 nm excitation. Upon heating, this compound undergoes an irreversible phase transition near 390 K associated with significant bond rearrangement. The high-temperature (HT) phase has a three-dimensinal (3D) perovskite-like structure. [(C3H7)4N][Cd(N(CN)2)3] is, therefore, the first example of a hybrid organic-inorganic dicyanamide exhibiting a temperature-induced reconstructive transition from a 2D (layered) structure to a 3D (perovskite-like) structure.