Pd Ions Research Articles

Exceptionally amino-quantitated 3D MOF@CNT-sponge hybrid for efficient and selective recovery of Au(III) and Pd(II)

• High-performance hybrid 30-MCNT was prepared for Au and Pd recovery. • 30-MCNT shows a superior selectivity to Au and Pd among other ten metals. • CNT sponge provides easier handpicked recycle framework to enhance recyclability. • Exceptional amino groups play the most critical roles for Au and Pd adsorption. • DFT simulation calculation elucidates interaction mechanisms during adsorption. Designing materials for selective recovery of precious metals is a critical challenge in response to recent outbreaks of electronic wastes owing to economic and environmental concerns. We introduced high-performance hybrid materials (MCNTs) comprising of six-amino groups based on hexaaminobenzene metal-organic framework (HAB-MOF) and carbon nano-tube (CNT) sponge for selective recovery of Au(III) and Pd(II). Among all MOFs ever reported in the literature, the particular synthesized 30-MCNT (30 mg HAB-MOF on CNT sponge) exhibited the highest adsorption capacity ( q e ) of 1832 mg/g (45 °C, pH 3.0) for Au(III) and 1651 mg/g (45 °C, pH 1.0) for Pd(II), which can be regarded as a benchmark in the MOF family. The highly selective nature of 30-MCNT was examined in the presence of ten different metal ions and the results showed that the Au(III)/Pd(II) adsorption efficiency was decreased by only 5–10%. Moreover, the Au(III) and Pd(II) recovery was maintained ∼ 100% from the initial solution with metal concentration of 200 mg/L. The superior performance was mainly attributed to the role of abundant amino groups in the hybrid framework, developing several types of interactions with Au(III) and Pd(II) ions such as hydrogen bonding, electrostatic interactions, acid-base affinity and π-π inner sphere complexation. Furthermore, the remarkably high surface area and robust chemical and mechanical stability of CNT-sponge provided an exceptional support for impregnation of HAB-MOF to avail greater active sites and easier handpicked recycle. Density functional theory (DFT) simulation and X-ray photoelectron spectroscopy (XPS) studies were employed to explore the interaction mechanisms during the adsorption processes. Owing to facile and environment-friendly synthesis, excellent recovery and recycling, the material can be possibly considered for industrial application in precious metal recovery.

New Pd(II) complexes of the bisthiocarbohydrazones derived from isatin and disubstituted salicylaldehydes: Synthesis, characterization, crystal structures and inhibitory properties against some metabolic enzymes.

Pd(II) complexes (Pd1, Pd2, and Pd3) were synthesized for the first time using asymmetric isatin bisthiocarbohydrazone ligands and PdCl2(PPh3)2. All complexes were characterized by a range of spectroscopic and analytical techniques. The molecular structures of Pd1 and Pd3 have been determined by single-crystal X-ray diffraction analysis. The complexes are diamagnetic and exhibit square planar geometry. The asymmetric isatin bisthiocarbohydrazone ligands coordinate to Pd(II) ion in a tridentate manner, through the phenolic oxygen, imine nitrogen and thiol sulfur, forming five- and six-membered chelate rings within their structures. The fourth coordination site in these complexes is occupied by PPh3 (triphenylphosphine). The free ligands and their Pd(II) complexes were evaluated for their carbonic anhydrase I, II (hCAs) and acetylcholinesterase (AChE) inhibitor activities. They showed a highly potent inhibition effect on AChE and hCAs. Ki values are in the range of 9 ± 0.6-30 ± 5.4nM for AChE, 7 ± 0.5-16 ± 2.2nM for hCA I and 3 ± 0.3-24 ± 1.9nM for hCA II isoenzyme. The results clearly demonstrated that the ligands and their Pd(II) complexes effectively inhibited the used enzymes.

Azo-chromophore based on functionalized silica nanotubes for enhanced identification of Pd(II) ions in e-residues

A bootstrap to build a novel solid chemical sensor was used functionalized by silica nanotubes (F-SNTs). This novel nanosized sensor has been developed to be immobilized directly on the F-SNTs with the new azo-chromophorous (z)-2-(2,4-dihydroxyphenyl)-terephthalic acid (HPDTP) using the two carboxylic acid groups. In the fluorescent technique detection range 5–825 ppb was achieved for Pd(II) ions, with linear correlation values of 0.9969. The new nanosized sensor has a high sensitivity for Pd(II) ions up to 28.8 ppb at extremely low concentration. This nanosized sensor was evaluated for its use as an adsorber. The sensor (HPDTP) has a fast detection feature for the removal without preconcentration of Pd(II) ions. This nanosized sensor also exhibits an effective Pd(II) identification in e-residues and preferential recovery.

Electrospun nanofibrous scaffolds of polycaprolactone containing binary ions of Pd/vanadate doped hydroxyapatite for biomedical applications

In this work, manipulation of scaffold compositions is executed, aiming to the enhancement of wound healing via the acceleration of the curing process and inhibition of bacterial growth. The study includes powder phase, palladium/vanadate hydroxyapatite (Pd/V-HAP), and fibrous phase (Pd/V-HAP@PCL) preparation in different Pd(II) ions contents. The structural inspection with palladium insertion is inspected for powder and nanofibrous compositions using XRD, while the morphological behavior was examined by the FESEM technique. The porous structure is detected clearly in the highest palladium composition in powder phase compositions, besides a significant reduction in fiber filament diameter from 4 μm to 1.5 μm. The roughness average of 0.8Pd/V-HAP@PCL shows detectable growing with palladium insertion reaching 23.6 and 103.7 nm for powder and fibrous phase, respectively. The narrowest contact angle is introduced by 0.8Pd/V-HAP@PCL scaffold with 88±3°, while it presented the highest cell viability with 95.1 ± 2%. Additionally, the 0.8Pd/V-HAP@PCL nanofibrous composite shows the maximum inhibition zones with 19.6 ± 0.8 and 18.7 ± 0.9 mm against E. coli and S. aureus microorganisms, respectively. It could be added that the cellular growth of fibroblasts cell line was observed via scanning microscope, where the spreading and the proliferation of cells increased upon the change of the compositions of nanofibers. The enlargement of the growing area of cells through the scaffold's surface might indicate the ability of these biomaterials for wound care potential applications.

Preparation of highly dispersed Pd/SBA-15 catalysts for dodecahydro-N-ethylcarbazole dehydrogenation reaction by ion exchange-glow discharge.

Dehydrogenation reactions are critical in hydrogen storage based on a liquid organic hydrogen carrier (LOHC) system. Speeding up the dehydrogenation rate and lowering the reaction temperature are the main focuses of LOHC dehydrogenation catalysts. In this paper, Pd/SBA-15 catalysts (Pd-IP/S15) were prepared by NaOH treatment of surface hydroxyl groups on SBA-15, the ion exchange of Na+ with Pd(NH3)42+, and then reduction of Pd ions via glow discharge plasma. The dehydrogenation performance of dodecahydro-N-ethylcarbazole on the prepared catalysts is studied. The turnover frequency of Pd-IP/S15 is 13.94 min-1 at 170°C, which is 10.25 times that of commercial Pd/C. It is ensured via the ion exchange method that Pd(NH3)42+ could be precisely targeted at the Si-OH of SBA-15 to form Si-O-Pd(NH3)42+, which effectively prevents the aggregation and uncontrollable growth of Pd nanoparticles (NPs) during the in situ reduction by plasma. Pd NPs with high dispersion are obtained on SBA-15, which enhances the catalytic activity of Pd-IP/S15. The coordination of Pd NPs with O of Si-OH on SBA-15 enabled Pd-IP/S15 to exhibit excellent catalytic stability. After 7 dehydrogenation cycles at 180°C, the dehydrogenation efficiency remained above 97%.

An Imidazole‐Rich Pd(II)‐Polymer Pre‐catalyst for the Suzuki‐Miyaura Coupling: Stability Influenced by Dissolved Oxygen and Reactants Concentration

AbstractHerein a novel Pd(II)‐polymeric pre‐catalyst was prepared by coordinating Pd(II) ions to a low cost imidazole/carboxylate‐rich polymer. The material displays good activity in the Suzuki‐Miyaura coupling towards a range of aryl bromides and iodides in iPrOH/H2O mixtures at 25 or 60 °C. Catalyst longevity and recyclability proved to be sensitive to the concentration of the cross‐coupling partners. When the concentration of PhBr is high ([PhBr]=250 mmol L−1), inactive Pd(0) aggregates were detected. On the other hand, when the reaction was performed at 20‐fold dilution ([PhBr]=12.5 mmol L−1) the material could be reused up to 12 times without significant loss of catalytic activity. In this condition, minimum amount of Pd(0) was detected by XPS analysis and no Pd(0) aggregates were observed by XRPD. Importantly, it was found that the presence of oxygen is fundamental for avoiding formation of inactive Pd(0) aggregates.

Microcapsules-supported Pd catalysts with ultralow ionic residues

Catalyst supports play an essential role in improving catalytic activity, preventing site loss, and promoting material diffusion. In this work, polyethyleneimine (PEI) microcapsules were prepared by interfacial crosslink polymerization on micro-droplets. The influence of reaction conditions on the formation of microcapsules was investigated in detail by combining the in-situ observation of optical microscope and kinetic modeling of interfacial polymerization. The obtained microcapsules can strongly absorb Pd2+ with an adsorption capacity of up to 1000 mg/g. The microcapsules-supported Pd (Pd/MCs) presented good catalytic activity for the Suzuki coupling reaction. The apparent activation energy was 28.3 kJ/mol. In addition, the catalyst demonstrated good recycling characteristics. The leakage rate of the Pd ion was less than 0.016%, and the residual amount of Pd in the reaction solution was lower than 0.099 ppm. Moreover, after repeatedly being used 10 times, the conversion efficiency of bromobenzene was maintained above 94%.

Elucidating the Role of CO in the NO Storage Mechanism on Pd/SSZ-13 with in Situ DRIFTS

Pd-ion-exchanged zeolites have emerged as promising materials for the adsorption and oxidation of air pollutants. For low-temperature vehicle exhaust, dispersed Pd ions can adsorb NOx even in H2O-rich exhaust containing carbon monoxide. To understand this phenomenon, changes in the Pd ligand environment have to be monitored in situ. Herein, we directly observe the activation of hydrated Pd ion shielded by H2O into a carbonyl–nitrosyl complex Pd2+(NO)(CO) in SSZ-13 zeolite. The subsequent thermal desorption of ligands on the Pd2+(NO)(CO) complex proceeds to nitrosyl Pd2+ rather than to carbonyl Pd2+ under various conditions. Thus, CO molecules act as additional ligands to provide an alternative pathway with a lower energy barrier in accelerating NO adsorption on hydrated Pd2+ ions through the Pd2+(NO)(CO) complex. We further demonstrate that hydration of Pd ions in the zeolite is a prerequisite for CO-induced reduction of Pd ions to metallic Pd. The reduction of Pd ions by CO is limited under dry conditions even at temperatures as high as 500 °C, while water makes it possible at near RT. However, the primary NO adsorption sites are Pd2+ ions even in gases containing CO and water. These findings clarify additional mechanistic aspects of the passive NOx adsorption (PNA) process and will help extend the NOx adsorption chemistry in zeolite-based adsorbers to practical applications.

Effect of N-benzyl group in indole scaffold of thiosemicarbazones on the biological activity of their Pd(II) complexes: DFT, biomolecular interactions, in silico docking, ADME and cytotoxicity studies

A series of N-benzyl substituted indole-based thiosemicarbazone (TSC) ligands (L4-L6) and palladium(II) TSC complexes, [Pd(L)2] (1–6) (L = monoanionic bidentate un/N-substituted indole-based TSC ligand) have been synthesized and characterized using analytical and spectroscopic tools. The exact molecular structures of L4-L6 and the complexes (2–4 and 6) were ascertained by single-crystal X-ray diffraction (XRD) method. Spectroscopic and crystallographic studies indicated that Pd(II) ion was coordinated with TSCs as monobasic bidentate ligands, forming two five-membered rings with square planar geometry. The effect of N-benzyl substitution in indole scaffold of TSCs in the complexes was studied using DFT method, and structure–activity relationships (SAR) were explored. The in silico ADME properties of the ligands and their complexes were thoroughly analyzed with respect to their lipophilicity and oral bioavailability. The complexes (1–6) exhibited strong intercalation with calf thymus DNA (CT DNA), which was examined by absorption/emission spectroscopic titrations and viscosity measurements. Similarly, the interaction of bovine serum albumin (BSA) with complexes examined using spectroscopic methods showed a strong binding between them. A better picture of various possible interactions was acquired from the molecular docking of the complexes with the targets like DNA, BSA, DNA Topoisomerase II and CASP3. In addition, in vitro cytotoxicity of the complexes was screened against two cancer (HeLa-S3 and A549) and one normal (IMR-90) cell lines. It was learnt that the N-benzyl substitution in the indole system inactivated the whole molecule by diminishing its anticancer activity. The unsubstituted indole TSC complex (2) displayed significant activity towards HeLa-S3 cells, and the results were compared with those of cisplatin. Beneficially, the active complex showed less toxicity against IMR-90 normal cells. Further, the results of AO-EB staining studies indicated that the complexes induced cell death via apoptosis pathway. The steric influence of the substituted indole moiety, its limited electronic effects and lesser stability in aqueous systems retarded the Pd(II) complexes of N-benzyl substituted indole TSCs from exhibiting their biological activities.

Separation of palladium and platinum metals by selective and simultaneous leaching and extraction with aqueous/non-aqueous solutions

The recovery of Pd and Pt from secondary resources has attracted much attention due to their unique chemical properties and economic values. The difference in the reduction potential of Pd(II) and Pt(IV) was utilized in the separation of the two metals by employing aqueous and non-aqueous solutions together. The two metals were selectively separated by employing simultaneous leaching and extraction occurred in one operation. A mixture of concentrated HCl, TBP (tributyl phosphate) in kerosene and H2O2 was able to selectively dissolve Pd over Pt metal and thus it was possible to separate the two metals by leaching and extraction. Replacement of H2O2 and kerosene with NaClO3 as an oxidizing agent and MIBK (methyl isobutyl ketone) as a polar diluent in the solvent mixture resulted in complete dissolution/extraction of Pt. The optimum conditions such as reaction time, temperature, stirring speed, the weight ratio of solid to HCl, TBP and oxidizing agents were obtained for the selective and complete leaching and extraction of Pd and Pt. The simultaneous leaching and extraction systems is more efficient than aqueous system of HCl and H2O2 in terms of selectivity and leaching ability for Pd. The Pd(II) and Pt(IV) ions in the loaded TBP phases were completely stripped by a mixture of HCl and thiourea and the purity of these metal ions in the respective stripping solutions was higher than 99.9%. A simple process can be developed to separate Pd and Pt metals by selective dissolution.

Корреляция между эффективностью генерации синглетного кислорода и параметрами люминесценции фотосенсибилизаторов

The quantum yield of interconversion to triplet states for free bases of 2,3,7,8,12,13,17,18-octaethylporphyrin and 5,10,15,20-tetraphenylporphyrin, as well as their metal complexes with Mg(II), Zn(II), Pd(II), and Pt(II) ions have been determined on the based on the data about efficiency of singlet oxygen generation. The quantum yields of singlet oxygen generation were measured for these compounds in several solvents. The maximum values of quantum yields of singlet oxygen generation are corresponding to compounds with heavy Pd(II) and Pt(II) ions, that is due to the high impact of the internal heavy atom on the spin-orbital coupling. High quantum yields of singlet oxygen generation for free bases of porphyrins indicate a significant role of spin-orbital coupling in the case without an internal heavy atom effect for these compounds. The effect of the internal heavy atom on the rates of deactivation of the lower triplet states for a porphyrins with Pd(II) and Pt(II) ions were detected at ambient and liquid nitrogen temperatures .

The upgrading role of Al at T1/T2 sites in stabilizing Pd ions over Pd-beta passive NOx adsorbers under a reducing atmosphere

The preserved Pd ions as γ and β sites related with Al at T1–T2 sites corresponded to the stabilized NOx storage capability and rendered a suitable desorption temperature.

A Novel Strategy for Preparing Metal-Organic Framework as a Smart Material for Selective Detection and Efficient Extraction of Pd(Ii) and Au(Iii) Ions from E-Wastes

A Novel Strategy for Preparing Metal-Organic Framework as a Smart Material for Selective Detection and Efficient Extraction of Pd(Ii) and Au(Iii) Ions from E-Wastes

Separation of Pd(II) and Pt(IV) ions using polymer inclusion membranes doped with alkylimidazoles

Separation of Pd(II) and Pt(IV) ions using polymer inclusion membranes doped with alkylimidazoles

Synthesis and characterization of a new 1-methyl imidazole derived ligand with its ionic complexes Pd(II) and Pt(IV) and study of biological activity as anticancer and antioxidant

The preparation and spectral identification of metal complexes for Pd(II) and Pt (IV) ions with new heterocyclic azo dye as ligand 2′[2′-(1-Hydroxy-4-methyl phenyl)azo] −1-methyl imidazole (HPA-1-MeI) were prepared by reacting diazonium chloride salt solution of 2-amino -4- methyl phenol with 1-methyl imidazole in alkaline ethanolic solution. Differing spectral techniques have been used to study the structures of the azo dye ligand (HPA-1-MeI) and chelate complexes such as elemental analysis (C.H.N), spectrum, 1H NMR, FT-IR, UV-Vis, XRD, thermal analysis (TGA-DTA), FE-SEM, and magnetic measurements. The molar conductivity indicates that the Pd(II) complex is not an electrolyte and does not contain conductive species, while the Pt(IV)-complex is the electrolyte because it contains Cl outside the coordination sphere. The results confirmed that the ligand (N, N, O) behaves as a tridentate and coordinates to the metal ion via the nitrogen atom of the azomethine group (CN) of heterocyclic imidazole molecule, nitrogen atom of the azo group (NN) which is the farthest of imidazole ring and the oxygen atom of the phenolic ring. Antioxidant studies of synthesized compounds were also performed by measuring the DPPH radical scavenging assay. The DPPH radical scavenging assay was used to measure the antioxidant activity of produced compounds and compared them with the known antioxidant ascorbic acid. However, in vitro anticancer and toxicity of ligand (HPA-1-MeI) and Pd (II)-Complex were assessed by MTT cytotoxicity assay against breast cancer cell line (MCF-7). Furthermore, molecular docking studies have been conducted on the potent compounds that have several crucial interactions with STI-571 proteins.

Photoluminescent polymer micelles with thermo-/pH-/metal responsibility and their features in selective optical sensing of Pd(ii) cations.

Photoluminescent polymers can be divided into two types of structures: one is the well-known conventional π-conjugated rigid chain polymers bearing π-conjugated chromophores in their side chains, and the other is the common flexible polymers without π-conjugated chromophores in their main or side chains but with a feature of clustering electron-rich and/or dipole groups in their main and/or side chains. In this work, we found a new photoluminescent polymer comprising theophylline (T) and imidazole (I) residues in a suitable ratio in the side chains on the common polystyrenic block (PVB-T/I). We synthesized a block copolymer (denoted as P2) consisting of hydrophobic PVB-T/I and hydrophilic poly(N-isopropylacrylamide), and we investigated its self-assembly into micelles and their micellar features, such as thermo-responsibility, fluorescence emission, pH, and metal ion-dependent photoluminescence, in detail. Especially, the micelles self-assembled from P2 showed intrinsic blue emission which was emitted from the charge transfer association between T and I residues in the intra-chains. Weakening the association by adjustment of the pH or addition of metal ions could evidently reduce the photoluminescence in the micellar state. Very interestingly, among many metal cations, only Pd2+, which can chelate strongly with theophylline, strongly quenched the photoluminescence from the micelles. Therefore, the polymer micelles functioned as an optical sensor for Pd(ii) ion not only by spectroscopy but also with the naked eye.

Bimetallic docked covalent organic frameworks with high catalytic performance towards coupling/oxidation cascade reactions.

Covalent organic frameworks (COFs) are an emerging class of crystalline porous polymers that make these materials suitable for use as excellent scaffold in heterogeneous catalysis. Here we synthesize a layered two-dimensional (2D) COF (TADP–COF) through the condensation reaction between four-branched 5,10,15,20-tetrakis(4-aminophenyl)porphyrin (TAPP) and linear 2,5-dihydroxyterephthalaldehyde (Dha) and 1,4-phthalaldehyde (PA) building blocks. Porphyrin units, imine and hydroxyl groups together with imines can provide wide coordination sites for metal docking. Using a programmed synthetic procedure, Cu(ii) ions first coordinated with the imine groups in conjunction with their adjacent hydroxyl groups, and porphyrin units and subsequently added Pd(ii) ions occupied the remaining imine sites in the space between adjacent COF layers. The bimetallic Pd(ii)/Cu(ii)@TADP–COF showed high catalytic activity in a one-pot coupling/oxidation cascade reaction in water. The high surface area, one-dimensional (1D) open channel structure and predesigned catalytic active sites of this material make it ideal candidate for use as heterogeneous catalyst in a wide range of catalytic reactions.

1,2-Bis[bis(pyridin-2-yl-methyl)phosphino]ethane and its PdCl2-based complex: synthesis and crystal structure

1,2-Bis[bis(pyridin-2-ylmethyl)phosphino]ethane, R2PCH2CH2PR2 (R = 2-PyCH2), has been synthesized in 92% yield via the reaction of Cl2PCH2CH2PCl2 with 2-[(trimethylsilyl)methyl]pyridine. Treatment of this phosphine with Pd(COD)Cl2 affords chelating complex of [PdLCl2] type, wherein the Pd(II) ion displays a square-planar [Pd@Cl2P2] geometry.

A DFT study on Ca-Alginate interactions with divalent transition metals

Alginate is a naturally occurring linear polysaccharide that is extracted from brown algae. This is generally produced as water-soluble Na alginate which in turn is transformed into water-insoluble Ca-Alginate beads. These beads are potential adsorbents for the removal of heavy metal ions from water through ion exchange with calcium ions present in the Ca-Alginate matrix. To investigate the feasibility of ion exchange of various heavy metal ions, Density Functional Theory (DFT) calculations were carried out using the Gaussian-16 simulation package. The heavy transition metal ions with + 2 valence in the 4th, 5th, and 6th periods of d-block were considered for the study as most of the heavy metals (e.g., Cu, Cr, Ni, Co, Mn, etc.) are present in this block and significantly contribute to water pollution. The widely accepted egg-box molecular model representation of alginate structures is used for computation purposes. For computation purposes, one monomer attached from top and bottom to the metal center is considered. The computations were carried out in both vapor and aqueous solvent phases and the trends of binding energy were found to be invariant. The binding energies of the alginate complexes formed with Ni, Pd, and Pt metal ions of the 4th, 5th, and 6th series were the highest amongst all the metals considered in this work.

Synthesis and characterization of organopalladium(II) complexes of N,N,S–tridentate sulfur-containing Schiff bases derived from 2-(2-pyridyl)benzothiazolines

The synthesis of mononuclear Pd(II) complexes of type [Pd(Ln)Me] (n = 1–4, 1a–4a) and dinuclear (η3–allyl)palladium(II) dichloro complexes [Pd2(Ln)(η3-C3H5)Cl2] (n = 1–3, 1b–3b) derived from 2-R-(2-pyridyl)benzothiazolines used as Schiff bases precursors (R = H, 1; R = Me, 2; R = Ph, 3; R = C5H4N-2, 4) is reported. The formation of the trinuclear complex [Pd3(L4)(η3-C3H5)2Cl3] (4c) and its behavior in solution is also described. Complexes 1a–4a, 1b–3b and 4c were obtained from the thiazole ring-opening reaction of precursors 1–4 in presence of the [Pd(tmeda)Me2] and [Pd(μ -Cl)(η3-C3H5)]2 starting materials. The {Ln}− anionic Schiff bases obtained showed a versatile behavior towards coordination to Pd(II) ion; in 1a–4a the ligand acted as tricoordinate whilst in 1b–3b and 4c, {Ln}− acted as mono- and tridentate ligand, respectively.1a–4a were stable complexes in DMSO‑d6 solution; the dinuclear 1b–3b and trinuclear 4c complexes showed the dissociation of S→Pd bond in DMSO‑d6 solution. Complexes 3a and 3b were characterized by X-ray diffraction studies and a distorted square planar geometry around the central Pd(II) ion was observed in the two five–membered chelate rings. A systematic analysis based on DFT calculation of the structural, electronic, and thermochemistry properties was performed for η3-ally complexes 1b–3b and 4c.