Cadmium Sites Research Articles

Investigating the structural, electronic, and magnetic properties of Cd1-xVxTe: Insights from First-Principles calculations

In our study, we aim to investigate the structural, electronic, and magnetic properties of CdVTe, a diluted magnetic semiconductor with a Cadmium telluride (CdTe) structure. To achieve this, we employ the full potential linear augmented plane wave method implemented in the CASTEP code, which allows us to accurately simulate the behavior of the system. To describe the electronic exchange and correlation effects, we adopt the generalized gradient approximation (GGA) within the density functional theory (DFT) framework. This choice of methodology ensures reliable and accurate calculations of the electronic and magnetic properties of Cd1-xVxTe. Our results reveal that the substitution of Vanadium (V) into the Cadmium (Cd) site of the CdTe lattice does not alter the zinc blende crystal structure, demonstrating the stability and structural integrity of the system. Furthermore, our calculations demonstrate that the introduction of Vanadium impurities leads to spin polarization within the material, resulting in the emergence of a magnetic moment. Notably, we find that a Vanadium concentration of approximately x≈0.12 exhibits the strongest magnetic properties, characterized by a significant magnetic moment. These findings provide valuable insights into the behavior and potential applications of CdVTe as a diluted magnetic semiconductor, shedding light on the interplay between structural, electronic, and magnetic properties in this material.

Local modification of the crystalline structure due to co-doping with RE3+ in cadmium metasilicate

Persistent emission is a well-known property of cadmium metasilicate (CdSiO3) doped and co-doped with rare earth ions due to the ease of choosing the desired luminescence colour, as well as the possibility of adjusting the emission colour and the luminescence duration. Experimental work has demonstrated that combinations of different rare earth ions can produce different emission spectra colours as well as modify the lifetime of emissions. Theoretical work demonstrated a preference of single dopants to substitute cadmium sites with a Cd-vacancy as a compensation mechanism. To help elucidate the luminescent mechanisms through structural modification and consequently modification of the crystal field generated in the material by the defective region, in this work, several configurations for combined defects were tested considering the distance and preferential configuration of all the defects that comprise the system, as well as the possibility of a high concentration of these defects. Results showed a preferential arrangement for the incorporation of a Cd-vacancy as a form of charge compensation. The arrangement forms an angle closer to 180° considering the Cd-vacancy as vertex and presents a distance of around 7 Å between rare earth ions. It was also identified that the formation of a single pair with two different RE3+ ions close to a cadmium vacancy are minimally energetically more favourable to be formed in relation to clusters of dopants and co-dopants. This indicates that at low doping concentrations, RE3+ dopant pairs will form separately, but by increasing the concentration it is possible to form a cluster of defects involving RE3+. This may explain the low concentrations of dopants in this matrix. The distortion caused in the local lattice by the presence of a RE3+ pair of different dopants is bigger than the distortion caused by a RE3+ pair of dopants of the same chemical species. Therefore, CdSiO3: RE13+, RE23+ has a crystal field that is different from the crystal field experienced by RE3+ as a single dopant and the presence of the co-dopant ion will modify the luminescence of the system even though the generating defect of the luminescent centre remains the same.

Influence of Capping Ligands, Solvent, and Thermal Effects on CdSe Quantum Dot Optical Properties by DFT Calculations.

Cadmium selenide nanomaterials are very important materials in photonics, catalysis, and biomedical applications due to their optical properties that can be tuned through size, shape, and surface passivation. In this report, static and ab initio molecular dynamics density functional theory (DFT) simulations are used to characterize the effect of ligand adsorption on the electronic properties of the (110) surface of zinc blende and wurtzite CdSe and a (CdSe)33 nanoparticle. Adsorption energies depend on ligand surface coverage and result from a balance between chemical affinity and ligand-surface and ligand-ligand dispersive interactions. In addition, while little structural reorganization occurs upon slab formation, Cd···Cd distances become shorter and the Se-Cd-Se angles become smaller in the bare nanoparticle model. This originates mid-gap states that strongly influence the absorption optical spectra of nonpassivated (CdSe)33. Ligand passivation on both zinc blende and wurtzite surfaces does not induce a surface reorganization, and thus, the band gap remains nonaffected with respect to bare surfaces. In contrast, structural reconstruction is more apparent for the nanoparticle, which significantly increases its highest occupied molecular orbital (HOMO)-lowest unoccupied molecular orbital (LUMO) gap upon passivation. Solvent effects decrease the band gap difference between the passivated and nonpassivated nanoparticles, the maximum of the absorption spectra being blue-shifted around 20 nm by the effect of the ligands. Overall, calculations show that flexible surface cadmium sites are responsible for the appearance of mid-gap states that are partially localized on the most reconstructed regions of the nanoparticle that can be controlled through appropriate ligand adsorption.

Covalent organic frameworks embedding single cadmium sites for efficient carboxylative cyclization of CO2with propargylic amines

Single cadmium sites on covalent organic frameworks promote adsorption and activation of CO2to efficiently catalyze cyclization of propargylic amines.

Identification of a Stable Ozonide Ion Bound to a Single Cadmium Site within the Zeolite Cavity

Molecular metal oxides are invoked as the key intermediate in a variety of oxidative reactions. Although an atomic oxygen ligand and molecular O2 ligands are well known, the triatomic oxygen ligand (ozonide) is very limited due to its instability. Here, we report a successful preparation and characterization of stable cadmium ozonide species. Our approach used the negatively charged local environments within the zeolite pore, which allowed us to isolate the single cadmium ozonide species as the counter cation even at room temperature. Its state was characterized by vibronic progressions closely similar to those observed in the cryogenic inert-element matrix system. Density functional theory calculations determined the lowest-energy geometry as the side-on [CdII(O3–•)]+ having C2v symmetry. This model was stable within the ab initio molecular dynamics simulation at 300 K, rationalizing the abnormal stability of [CdII(O3–•)]+observed experimentally. The O3-a1 → Cd-5s-donation orbital interaction was the driving force for the formation of the stable CdII–(O3–•) bond. The zeolite lattice plays a pivotal role in the enhancement of the acidity of the cadmium ion and stabilizes the donation interaction but constrains the O3 adduct as a pseudo-free ozonide ion. The findings in the present work will be applicable for designing new metal ozonide compounds.

Residential Proximity to Metal-Containing Superfund Sites and Toenail Metal Concentrations in a Nationwide Study of US Women

BACKGROUND AND AIM: Superfund sites in the United States contain hazardous substances, including toxic metals, which could potentially expose those living nearby. However, it is unclear whether residential proximity to sites may increase body burden of toxic metals. We aimed to evaluate the association between residential proximity to metal-containing Superfund sites and toenail metal concentrations. METHODS: Metal concentrations (aluminum, antimony, arsenic, cadmium, and lead, ng/g) were measured in toenail clippings collected between 2003-2009 in 2,998 women with a family history of breast cancer. Residential proximity to Superfund sites was measured by living ≤5 or 10 miles of a site (yes/no), site density (sites/mile^2) and an inverse-weighted sum distance measure (sites/mile). Linear regression was used to estimate the difference in toenail metal concentrations and 95% confidence intervals (CIs) per unit change in residential proximity measures (β). We evaluated whether associations varied by race/ethnicity. RESULTS:Women who lived closer to, or had a higher residential density of, Superfund sites reporting contamination of lead or antimony had higher toenail concentrations of the corresponding metals. For example, living ≤5-miles of a lead site was associated with 0.37 ng/g higher lead concentrations (95% CI: 0.18-0.57), and an increase in 1 additional lead-containing site/mile^2 was associated with 2.9 ng/g higher lead concentrations (95% CI: 1.8-4.0). Negligible associations were observed for sites containing arsenic or aluminum for any distance metric. For cadmium, associations were only evident in non-Hispanic Black women living near Superfund sites (N=744) but not non-Hispanic White women (N=2,244, e.g., living ≤5-miles of a cadmium site, βNon-Hispanic Black= 0.69, CI: 0.37-1.0; βNon-Hispanic white = -0.04, CI: -0.3-0.23; p-heterogeneity=0.02). CONCLUSIONS:Increased residential proximity to Superfund sites was associated with higher toenail concentrations of certain metals. Results for cadmium suggest important racial/ethnic differences in exposure that warrant follow-up for potential issues of environmental justice. KEYWORDS: chemical exposures, hazardous waste, heavy metals

Synthesis, crystal structure, high-resolution l13Cd and 13C MAS NMR investigation and dielectric study of [C2H10N2]Cd (SCN)4

A new crystalline polymer compound [C2H10N2]Cd (SCN)4 was synthesized and analyzed using XRD single crystal, differential scanning calorimetry (DSC), thermal gravimetric analysis (TGA), complex impedance and solid state 13C and 113Cd CP/MAS NMR. The crystal structure shows that the cadmium atoms have a S4N2-hexa-coordination sphere, exhibiting pseudo-octahedral geometry. The Cd(II) atoms are bridged by two SCN− anions generating 1D polymeric chains. Crystal packing with significantly different interactions was determined by Hirshfeld surface analysis and discussed herein. The crystal packing was assured by mean of hydrogen bonds, Van der Waals and π-π interactions. Solid state 113Cd CP/MAS NMR shows that each distinct cadmium site in the cadmium thiocyanates exhibits multiplets that result from 113Cd,14N spin-spin coupling. Examination of the 13C CP/MAS NMR line shapes allows direct measurement of the indirect spin-spin coupling constants 1J(14N, 13C) = 28 Hz and 2J(111/113Cd,13C) = (75+8)Hz, for the unique N-bonded thiocyanate ligand. DSC analysis shows a phase transition at about 359 K. The temperature dependence of bulk conductivity σ(Rp) and relaxation frequency (fr) were described and discussed by the use of the Arrhenius relationship. The frequency dependence of the real part of the AC conductivity in both phases follows the Jonscher's universal dynamic law. The evolution of S(T) as function of temperatures suggests that the quantum mechanical tunneling QMT mechanism prevails in phases I and II.

Cd2 and Co2 dumbbell formation in the yttrium-rich intermetallic compounds Y14Ni3Cd3 and Y6Co2Zn

Abstract The yttrium-rich intermetallic compounds Y14Ni3Cd3 and Y6Co2Zn were obtained by direct reactions of the elements in sealed tantalum tubes in an induction furnace. Both samples were characterized by X-ray powder diffraction and the structures were refined from single-crystal X-ray diffraction data: Lu14Co3In3 type, P42/nmc, a = 960.06(5), c = 2314.9(1) pm, wR2 = 0.0669, 2034 F 2 values, 63 parameters for Y14Ni3.16(2)Cd2.84(2) and Ho6Co2Ga type, Immm, a = 943.08(7), b = 950.08(7), c = 997.64(7) pm, wR2 = 0.0476, 981 F 2 values, 34 parameters for Y6Co2Zn. One cadmium site shows a small degree of Cd/Ni mixing, leading to the composition Y14Ni3.16(2)Cd2.84(2). Although both compounds crystallize with significantly different structure types, they show very similar monomeric building units: (i) transition metal centered trigonal prisms of yttrium, (ii) empty Y6 octahedra and (iii) icosahedral coordination of the cadmium respectively zinc atoms. The condensation patterns of these building units are discussed and for Y14Ni3.16(2)Cd2.84(2), we elaborate a crystal chemical building principle along with the rare earth metal-rich phases RE 15Rh5Cd2 (La15Rh5Cd2 type), RE 23 T 7 X 4 (Pr23Ir7Mg4 type), RE 4 TX (Gd4RhMg type) and RE 10 TX 3/RE 9 TX 4 (ordered Co2Al5 versions). The structures of Y14Ni3Cd3 and Y6Co2Zn show dumbbell formation: 306 pm Cd–Cd in Y14Ni3Cd3 and 224 pm Co1–Co1 and 246 pm Co2–Co2 in Y6Co2Zn.

Unravelling the possibility of hydrogen storage on naphthalene dicarboxylate-based MOF linkers: a theoretical perspective

Post-synthetic modification of organic linkers embedded in a metal–organic framework (MOF) is a favourable strategy to improve the storage of hydrogen through physisorption at ambient conditions. Density functional and domain-based local pair natural orbital coupled cluster calculations are conducted to evaluate the feasibility of hydrogen adsorption on open metal sites of a Napthalene Dicarboxylate-based linker. Both alkaline metal ions like Ca2+ and Mg2+ and transition metal ions like Zn2+ and Cd2+ are chosen for this study. DFT and DLPNO-CCSD(T) energies reveal that the Napthalene Dicarboxylate systems with open magnesium, zinc and cadmium sites are capable of reversible H2 binding. However, the adsorption energy with calcium is rather low precluding build-up of H2 on CaNDC coordination site. Furthermore, local energy decomposition analysis reveals charge transfer interaction is dominant in small ions like magnesium while exchange interaction of same spin electrons governs the complexation energy in transition metals like zinc and cadmium.

Влияние радиационных дефектов на электрофизические и детекторные свойства CdTe:Cl, облученного нейтронами

A promising material for semiconductor detectors of ionizing radiation is CdTe:Cl which allows obtaining detectors with high resistivity ρ and electron mobility μn. During operation, the detector materials may be exposed to neutron irradiation, which causes radiation defects to form in crystal lattice and deep levels to appear in the band gap, acting as centers of capture and recombination of nonequilibrium charge carriers, thus reducing the detection capability. The aim of this study was to use computer simulation to investigate the mechanisms of the influence of such radiation defects on the electrophysical properties (ρ, μn) of CdTe:Cl and the charge collection efficiency η of radiation detectors based on this material. The simulations were based on the models tested for reliability. It was found that the increase of the CdTe:Cl resistivity ρ during low-energy neutrons bombardment and at the initial stages of high-energy neutrons bombardment is caused by an increase in the concentration of radiation donor defect Z (with an energy level EC – 0.47 eV), presumably interstitial tellurium, which shifts the Fermi level into the middle of the band gap. The sharp rise of ρ observed at high-energy neutron bombardment is probably caused by the restructuring of the crystalline structure of the detector material with a change in the lattice constant and with an increase of the band gap, accompanied by a change in the conductivity properties. The degradation of the detector properties of CdTe:Cl during neutron irradiation is due to the capture and recombination of nonequilibrium electrons at radiation defects: Te interstitial, Te substitutional at the cadmium site, on tellurium vacancies and cadmium vacancies. The degradation of electron mobility μn can be caused by the scattering of electrons at microscopic areas of radiation defect clusters. The increase in concentration of the defects over the volume of the crystal at their uniform distribution of up to 1016 cm–3 does not significantly affect the electron mobility at room temperature.

A DFT/ZORA Study of Cadmium Magnetic Shielding Tensors: Analysis of Relativistic Effects and Electronic-State Approximations.

Theoretical considerations are discussed for the accurate prediction of cadmium magnetic shielding tensors using relativistic density functional theory (DFT). Comparison is made between calculations that model the extended lattice of the cadmium-containing solids using periodic boundary conditions and pseudopotentials with calculations that use clusters of atoms. The all-electron cluster-based calculations afford an opportunity to examine the importance of (i) relativistic effects on cadmium magnetic shielding tensors, as introduced through the ZORA Hamiltonian at either the scalar (SC) or spin-orbit (SO) levels and (ii) variation in the class of the DFT approximation. Twenty-three combinations of pseudopotentials or all-electron methods, DFT functionals, and relativistic treatments are assessed for the prediction of the principal components of the magnetic shielding tensors of 30 cadmium sites. We find that the inclusion of SO coupling can increase the cadmium magnetic shielding by as much as ca. 1100 ppm for a certain principal values; these effects are most pronounced for cadmium sites featuring bonds to other heavy atoms such as cadmium, iodine, or selenium. The best agreement with experimental values is found at the ZORA SO level in combination with a hybrid DFT method featuring a large admixture of Hartree-Fock exchange such as BH&HLYP. Finally, a theoretical examination is presented of the magnetic shielding tensor of the Cd(I) site in Cd2(AlCl4)2.

Crystalline Superlattices of Nanoscopic CdS Molecular Clusters: An X-ray Crystallography and 111Cd SSNMR Spectroscopy Study.

Systematic 111Cd solid-state (SS) NMR experiments were performed to correlate X-ray crystallographic data with SSNMR parameters for a set of CdS-based materials, varying from molecular crystals of small complexes [Cd(SPh)4]2- and [Cd4(SPh)10]2- to superlattices of large monodisperse clusters [Cd54S32(SPh)48(dmf)4]4- and 1.9 nm CdS. Methodical data analysis allowed for assigning individual resonances or resonance groups to particular types of cadmium sites residing in different chemical and/or crystallographic environments. For large CdS frameworks, 111Cd resonances were found to form three groups. This result is noteworthy, since for related systems with size polydispersity and variations in composition, such as CdS or CdSe nanoparticles protected with an organic ligand shell, typically only two groups of resonances were observed. The generalized information obtained in this work can be used for the interpretation of 111/113Cd SSNMR data for large CdS clusters and nanoparticles, for which crystal structure analysis remains inaccessible. Comparison of the powder X-ray diffraction patterns for freshly prepared and dried superlattices of large CdS clusters revealed an interesting superstructure rearrangement that was not observed for the smaller frameworks.

Influence of Se and Zn substitution on the electronic transport on a CdTe nanotube-based molecular device: a first-principles study

The electronic transport property of pure cadmium telluride (CdTe) nanotube, selenium-substituted and zinc-substituted CdTe nanotube-based molecular device are investigated with density functional theory. The electronic transport property of CdTe nanotube is studied in terms of device density of states (DOS), electron density, transmission spectrum, and transmission pathways. The substitution of selenium and zinc atoms along the left electrode and bias voltage has the impact in the DOS. The electron density is found to be more at cadmium site in the left electrode. The transmission spectrum provides the insight into the transmission of electrons from valence band to conduction band across CdTe nanotube. The transmission pathway provides the visualization of electron transmission along CdTe nanotube. The results of present work provide a clear vision to tailor CdTe nanostructures with enhanced electronic property with substitution impurity for optoelectronic devices and photovoltaic cells.

First-principles studies on electronic transport properties of CdS nanoribbon based molecular device

The electronic transport properties of cadmium sulfide nanoribbon based molecular device were investigated by employing first principles calculation using density functional theory. The electronic properties are discussed in terms of density of states spectrum and electron density. The density of states of charge depends on the applied bias voltage. The electron density is seen more at cadmium sites. The transport properties of CdS nanoribbon are studied using transmission coefficient spectrum and transmission pathways. The electronic transmission all along the scattering region depends on the bias voltage; depending upon the bias voltage the transmission path also gets altered. The information provided in the present study will pave way to tailor nanostructures with improved performance in nanoelectronic devices.

Quantum Confinement Controls Photocatalysis: A Free Energy Analysis for Photocatalytic Proton Reduction at CdSe Nanocrystals

The ability to adjust the mechanical, optical, magnetic, electric, and chemical properties of materials via the quantum confinement effect is well-understood. Here, we provide the first quantitative analysis of quantum-size-controlled photocatalytic H2 evolution at the semiconductor-solution interface. Specifically, it is found that the hydrogen evolution rate from illuminated suspended CdSe quantum dots in aqueous sodium sulfite solution depends on nanocrystal size. Photoelectrochemical measurements on CdSe nanocrystal films reveal that the observed reactivity is controlled by the free energy change of the system, as determined by the proton reduction potential and the quasi-Fermi energy of the dots. The corresponding free energy change can be fitted to the photocatalytic activity using a modified Butler-Volmer equation for reaction kinetics. These findings establish a quantitative experimental basis for quantum-confinement-controlled proton reduction with semiconductor nanocrystals. Electrochemical data further indicate that proton reduction occurs at cadmium sites on the dots, and that charge separation in these nanocrystals is controlled by surface effects, not by space charge layers.

Probing Spin Density and Local Structure in the Prussian Blue Analogues CsCd[Fe/Co(CN)6]⋅0.5 H2O and Cd3[Fe/Co(CN)6]2⋅15 H2O with Solid‐State MAS NMR Spectroscopy

Magic-angle spinning (MAS) NMR spectroscopy is used to study the local structure and spin delocalisation in Prussian blue analogues (PBAs). We selected two common archetypes of PBAs (A(I)M(II)[M(III)(CN)(6)]·xH(2)O and M(II)(3)[M(III)(CN)(6)](2)·xH(2)O, in which A(I) is an alkali ion, and M(II) and M(III) are transition-metal ions) that exhibit similar cubic frameworks but different microscopic structures. Whereas the first type of PBA contains interstitial alkali ions and does not exhibit any [M(III)(CN)(6)](3-) vacancies, the second type of PBA exhibits [M(III)(CN)(6)](3-) vacancies, but does not contain inserted alkali ions. In this study, we selected Cd(II) as a divalent metal in order to use the (113)Cd nuclei (I=1/2) as a probe of the local structure. Here, we present a complete MAS NMR study on two series of PBAs of the formulas Cd(II)(3)[Fe(III)(x)Co(III)(1-x)(CN)(6)](2)·15H(2)O with x=0 (1), 0.25 (2), 0.5 (3), 0.75 (4) and 1 (5), and CsCd(II)[Fe(III)(x)Co(III)(1-x)(CN)(6)]·0.5H(2)O with x=0 (6), 0.25 (7), 0.5 (8), 0.75 (9) and 1 (10). Interestingly, the presence of Fe(III) magnetic centres in the vicinity of the cadmium sites has a magnifying-glass effect on the NMR spectrum: it induces a striking signal spread such that the resolution is notably improved compared to that achieved for the diamagnetic PBAs. By doping the sample with varying amounts of diamagnetic Co(III) and comparing the NMR spectra of both types of PBAs, we have been able to give a view of the structure which is complementary to that usually obtained from X-ray diffraction studies. In particular, this study has shown that the vacancies are not randomly distributed in the mesoporous PBAs. Moreover the cadmium chemical shift, which is a measure of the hyperfine coupling, allows the estimation of the spin density on the cadmium nucleus, and consequently, the elucidation of the spin delocalisation mechanism in these compounds along with its dependency on structural parameters.

Characterization of Primary Amine Capped CdSe, ZnSe, and ZnS Quantum Dots by FT-IR: Determination of Surface Bonding Interaction and Identification of Selective Desorption

Surface ligands of semiconductor quantum dots (QDs) critically influence their properties and functionalities. It is of strong interest to understand the structural characteristics of surface ligands and how they interact with the QDs. Three quantum dot (QD) systems (CdSe, ZnSe, and ZnS) with primary aliphatic amine capping ligands were characterized primarily by FT-IR spectroscopy as well as NMR, UV-vis, and fluorescence spectroscopy, and by transmission electron microscopy (TEM). Representative primary amines ranging from 8 to 16 carbons were examined in the vapor phase, KBr pellet, and neat and were compared to the QD samples. The strongest hydrogen-bonding effects of the adsorbed ligands were observed in CdSe QDs with the weakest observed in ZnS QDs. There was an observed splitting of the N-H scissoring mode from 1610 cm(-1) in the neat sample to 1544 and 1635 cm(-1) when bound to CdSe QDs, which had the largest splitting of this type. The splitting is attributed to amine ligands bound to either Cd or Se surface sites, respectively. The effect of exposure of the QDs dispersed in nonpolar medium to methanol as a crashing agent was also examined. In the CdSe system, the Cd-bound scissoring mode disappeared, possibly due to methanol replacing surface cadmium sites. The opposite was observed for ZnSe QDs, in which the Se-bound scissoring mode disappeared. It was concluded that surface coverage and ligand bonding partners could be characterized by FT-IR and that selective removal of surface ligands could be achieved through introduction of competitive binding interactions at the surface.

A new one-dimensional hybrid material lattice: AC conductivity and structural characterization of [C7H12N2][CdCl4

The present paper reports the synthesis, crystal structure, 13C and 111Cd cross-polarization magic-angle spinning nuclear magnetic resonance(CP-MAS-NMR) analysis and ac conductivity for a new organic–inorganic hybrid salt, [C7H12N2][CdCl4]. The compound crystallizes in the triclinic system, space group P $$ \overline 1 $$ , with unit cell dimensions: a = 7.1050(3) A, b = 8.9579(3) A, c = 9.4482(3) A, α = 81.415(1)°, β = 89.710(2)°, γ = 85.765(1)°, V = 592.97(4) A3, and Z = 2. The asymmetric unit is composed of one-2,4-diammonium toluene cation and one [CdCl4]2− anion. The Cd atom is in a slightly distorted octahedra coordination environment. Its structure can be described by infinite chains of CdCl6 octahedron linked to organic cations by a strong charge-assisted N–H∙∙∙Cl interactions in order to build organic–inorganic layers staked along $$ \left[ {0\overline 1 1} \right] $$ direction. The solid state 13C CP-MAS-NMR spectra has shown seven isotropic resonances, confirming the existence of seven non-equivalent carbon atoms, which is consistent with crystal structure determined by X-ray diffraction. As for 111Cd MAS-NMR, it has shown one cadmium site with isotropic chemical shift observed at 167.2 ppm. The complex impedance of the compound has been investigated in the temperature range of 403–460 K and in the frequency range of 200 Hz–5 MHz. The impedance plots have shown semicircle arcs at different temperatures and an electrical equivalent circuit has been proposed to explain the impedance results. The circuits consist of the parallel combination of bulk resistance R p and constant phase elements.

Syntheses, structures and properties of coordination polymers of cadmium(ii) with 4-methyl-1,2,4-triazole-3-thiol ligand

Hydro(solvo)thermal reactions of cadmium(II) salts with 4-methyl-1,2,4-triazole-3-thiol (Hmptrz) afforded six novel cadmium(II) coordination polymers, namely, [Cd(mptrz)2]n (1), [Cd(mptrz)X]n (X = Br (2) and I (3)), [Cd(mptrz)(μ2-X)]n (X = Br (4) and Cl (5)), and [Cd3(μ3-OH)2(mptrz)4]n (6). Compound 1 is a 1D looped chain structure. Compounds 2 and 3 are isostructural and have 1D ladder structures. Compounds 4 and 5 are isomorphs and feature 2D layered structures. Cadmium(II) bromide formed 1D ladder of 2 and 2D layer of 4, representing an unusual example of Br bond isomerism. Compound 6 has a 1D tape structure with an uncommon 1D inorganic ⋯Cd2(μ3-OH)2–Cd–Cd2(μ3-OH)2⋯ chain. The structural diversity of these materials is reflected in the variety of coordination polyhedra displayed by the cadmium sites: tetrahedral; trigonal bipyramidal; octahedral. The solid state photoluminescence of all compounds have been investigated. However, only compound 6 exhibits photoluminescence with an emission maximum at 435 nm upon excitation at 346 nm. Solid-state density functional theory (DFT) calculations were performed on compound 6. In addition, these compounds were characterized by IR, elemental analysis, and thermogravimetric analysis.

Structural analysis of actinidin and a comparison of cadmium and sulfur anomalous signals from actinidin crystals measured using in-house copper- and chromium-anode X-ray sources

The structure of the 24 kDa cysteine protease saru-actinidin from the fruit of Actinidia arguta Planch. (sarunashi) was determined by the cadmium/sulfur-SAD method with X-ray diffraction data collected using in-house Cu Kα and Cr Kα radiation. The anomalous scatterers included nine sulfurs and several cadmium ions from the crystallization solution. The high quality of the diffraction data, the use of chromium-anode X-ray radiation and the substantial anomalous signal allowed structure determination and automated model building despite both a low solvent content (<40%) and low data multiplicity. The amino-acid sequence of saru-actinidin was deduced from the cDNA and was modified based on experimental electron-density maps at 1.5 Å resolution. The active site of saru-actinidin is occupied by a cadmium ion and the active-site cysteine is found to be in an unmodified, cysteine sulfenic acid or cysteine sulfinic acid form. The cadmium sites, coordination geometries and polygonal water structures on the protein surface have also been extensively analyzed. An analysis and comparison of the sulfur/cadmium anomalous signals at the Cu Kα and Cr Kα wavelengths was carried out. It is proposed that the inclusion of cadmium salts in crystallization solutions coupled with chromium-anode radiation can provide a convenient route for structure determination.