Anionic Complexes Research Articles

Mesomorphism and luminescence in coordination compounds and ionic salts based on pyridine-functionalized β-diketones. Influence of the pyridine nitrogen position

Pyridine-functionalized β-diketones with the pyridine nitrogen atom at 3 or 4 position (L3N and L4N, respectively) have been used as building blocks to obtain two new families of compounds with mesomorphic and luminescent behaviors. The N-pyridine coordination of the β-diketones to zinc(II), palladium(II) and platinum(II) metal centers has allowed to synthesize neutral coordination compounds of the type [MCl2(LZN)2] (M = Zn(II), Pd(II), Pt(II); Z = 3, 4). Particularly, coordination of L4N towards Pt(II) gives rise to the cationic species [Pt(NH3)2(L4N)2]2+. Otherwise, protonation of the pyridine moiety was strategically used to obtain a novel series of pyridinium ionic salts of the type (HLZN)nA (n = 1, A = Cl; n = 2, A = MCl4, M = Zn(II), Pd(II), Pt(II); Z = 3, 4). The neutral or ionic nature of the complexes, as well as the β-diketone ligands and the metal center in both the neutral and anionic complexes, has a great influence on the mesomorphic behavior. Thus, columnar or smectic mesophases can be selectively formed. Single-crystal and temperature-dependent powder X-ray diffraction studies have been performed to analyze the molecular packing in the crystal and the supramolecular ordering in the mesophase. All the aforementioned factors also play a key role on the luminescence properties, the Zn(II) coordination compounds and ionic salts being the best candidates as bifunctional materials.

Novel synthesis and evaluation of anion-π interactions in one-walled meso-cyanophenyl substituted calix[4]pyrrole (C4P): Experimental and computational insights

A novel one-walled meso-cyanophenyl functionalized calix[4]pyrrole (4) was synthesized from cyanophenyl appended dipyrromethane (3) through conventional strategy and also by utilizing deep eutectic solvent of N,N'-dimethyl urea (DMU) & L-(+)-tartaric acid (TA) in a ratio of 7:3. The structural confirmation of 4 was done through 1H-NMR, 13C-NMR, FT-IR, and HRMS spectral data. Anion binding studies of the receptor 4 with several anions (halides, trigonal oxoanions, tetragonal oxoanions, etc.) used as tetrabutylammonium (TBA) salts, were successfully investigated by virtue of UV–Vis spectroscopy and time dependent density functional theory (TD-DFT). Notably, the UV–Vis absorbance titrations performed in CH3CN solvent, revealed significantly higher anion binding of receptor 4 with F¯, Cl¯, Br¯, and SCN¯ in comparison to the simple C4P. This can be ascribed to the fact that the cyanophenyl moiety is π-acidic in nature which participates in anion complexation through weak anion-π interactions (observed through 1H-NMR spectroscopy) and hence modulates anion binding through cooperative effect of preliminary NH-hydrogen bonding due to C4P scaffold and anion-π contacts due to cyanophenyl moiety.

Chelate complexed multi-elemental printing performance of a small and cost efficient picoliter droplet printing device for micro preparation

We introduce an inexpensive modular picoliter pipetting device using modified commercially available thermal inkjet cartridges. The system is capable of reliable deposition of 65 elements. The printing solutions were modified to prevent the dissolution of Ni from the nozzle head, keeping those at a pH of >9. Loss of cations to the glass surfaces inside the nozzle head is prevented by forming anionic complexes with ethylenediaminetetraacetic acid in basic conditions. For some elements, e.g., Si, additives like tetramethylammonium hydroxide are necessary.The volumes of the droplets were obtained, weighing 30,000–360,000 droplets ejected by the printer using a laboratory scale. The droplet volume was within a range of 142–184 pL, depending on the formulation. The delivered elemental masses and the reproducibility were determined using total reflection X-ray fluorescence analysis and inductively coupled plasma optical emission spectrometry. Delivered masses were in the range of 0.98 pg – 11.9 pg per element and droplet.The shape of deposits of about 31 pg per element was studied using atomic force microscopy, optical microscopy, and confocal laser scanning microscopy. They were mostly spherical and ca. 14 μm in diameter and ca. 2 μm in height. The broad range of printable elements allows for the micro preparation of solid compounds for establishing a grazing incidence X-ray diffraction analysis library. As an example, the MgAl2O4 spinel was synthesized by printing of the formulation and subsequent calcination. Here we show its performance for the preparation of minerals in the context of recycling of critical elements from pyrometallurgical slags.

Controllable molecular orientation at the interface and coordination with second hydration-sphere to enhance separation of Pt(IV) and Pd(II) in hydrochloric acid solutions: Mass transfer based separation and molecular dynamics

In conventional liquid-liquid extraction, Pt(IV) and Pd(II) chloride complex anions PtCl62− and PdCl42− in concentrated hydrochloric acid cannot be separated using simple amine extractants according to the ion association mechanism based on the thermodynamic difference in the interaction of their inner sphere coordinated chloride ions with protonated amine. This study exhibits a novel strategy for enhancing the separation of PtCl62− and PdCl42− anions using thin-layer organic membrane-based laminar flow (TOMLF) extraction by controlling the acidified primary amine N1923 (A-N1923) molecular orientation on the surface of concentrated hydrochloric acid with a laminar shear flow. Experiments revealed that the separation selectivity is primarily determined by the interaction of A-N1923 molecules with the outer sphere-bound water molecules around PtCl62− and PdCl42− anions, and is easily controlled by regulating the A-N1923 molecular orientation on the surface of laminar flow. It is a new phenomenon that has not been previously documented. The evolution of A-N1923 molecular orientation and complexation sites induced by laminar shear flow would result in a controllable spatial geometry recognition, therefore promoting or inhibiting the separation of PtCl62− and PdCl42− anions in concentrated hydrochloric acid. This work is expected to provide new insight into the development of hydration-sphere coordination strategies based upon shear-switch laminar flow for controllable host-guest molecule recognition at a flowing liquid-liquid interface.

Synthesis of trioctyl polyvinyl chloride ammonium, membrane extraction properties, and electrodriven mass transfer behavior of Chromium (VI)

Trioctyl polyvinyl chloride ammonium (PVCTQAS) with quaternary ammonium salt content (QAS) of 25 % was synthesized by a nucleophilic substitution reaction of between polyvinyl chloride (PVC) and trioctylamine (TOA) for the first time. The mass transfer behavior of HCrO4−, CdCl3−, CoCl42−, FeCl4−, and CuCl42− metal complex anions within the plasticized PVCTQAS membrane followed a first-order kinetic rate equation. Taking the Cr(Ⅵ)-PVCTQAS system as a representative, the influences of plasticizer content and membrane thickness on the mass transfer performance were investigated, and the electrodriven mass transfer behavior of Cr(VI) was studied. The results showed that the mass transfer of HCrO4− in PVCTQASD followed a jumping mechanism, with a QAS content threshold of 22 %. In the Cr(VI)-PVCTQAS electrodriven mass transfer system, the PVCTQASD exhibited uniform electrochemical properties, and the membrane thickness had little influence on the mass transfer rate. The response of HCrO4− mass transfer rate to voltage depended on the distribution density of QAS in the membrane. The mass transfer performance of PVCTQASD with QAS between 15 % and 20 % had a high dependence on the voltage, while the permeability coefficient of Cr(VI)-PVCTQAS system became stable when the voltage exceeded 10 V after surpassing the QAS content threshold. 50 μm QAS 25 % Cr(VI)-PVCTQAS system had a treatment efficiency of 710 mg·m−2·h−1 for HCrO4− at 10 V, while maintaining exceptional selectivity and stability.

Hydroxylated Polyoxometalate with Cu(II)- and Cu(I)-Aqua Complexes: A Bifunctional Catalyst for Electrocatalytic Water Splitting at Neutral pH.

A sole inorganic framework material [Li(H2O)4][{CuI(H2O)1.5} {CuII(H2O)3}2{WVI12O36(OH)6}]·N2·H2S·3H2O (1) consisting of a hydroxylated polyoxometalate (POM) anion, {WVI12O36(OH)6}6-, a mixed-valent Cu(II)- and Cu(I)-aqua cationic complex species, [{CuI(H2O)1.5}{CuII(H2O)3}2]5+, a Li(I)-aqua complex cation, and three solvent molecules, has been synthesized and structurally characterized. During its synthesis, the POM cluster anion gets functionalized with six hydroxyl groups, i.e., six WVI-OH groups per cluster unit. Moreover, structural and spectral analyses have shown the presence of H2S and N2 molecules in the concerned crystal lattice, formed from "sulfate-reducing ammonium oxidation (SRAO)". Compound 1 functions as a bifunctional electrocatalyst exhibiting oxygen evolution reaction (OER) by water oxidation and hydrogen evolution reaction (HER) by water reduction at the neutral pH. We could identify that the hydroxylated POM anion and copper-aqua complex cations are the functional sites for HER and OER, respectively. The overpotential, required to achieve a current density of 1 mA/cm2 in the case of HER (water reduction), is found to be 443 mV with a Faradaic efficiency of 84% and a turnover frequency of 4.66 s-1. In the case of OER (water oxidation), the overpotential needed to achieve a current density of 1 mA/cm2 is obtained to be 418 mV with a Faradaic efficiency of 80% and turnover frequency of 2.81 s-1. Diverse electrochemical controlled experiments have been performed to conclude that the title POM-based material functions as a true bifunctional catalyst for electrocatalytic HER as well as OER at the neutral pH without catalyst reconstruction.

Cation Co-Intercalation with Anions: The Origin of Low Capacities of Graphite Cathodes in Multivalent Electrolytes.

Dual-ion batteries involving anion intercalation into graphite cathodes represent promising battery technologies for low-cost and high-power energy storage. However, the fundamental origins regarding much lower capacities of graphite cathodes in earth abundant and inexpensive multivalent electrolytes than in Li-ion electrolytes remain elusive. Herein, we reveal that the limited anion-storage capacity of a graphite cathode in multivalent electrolytes is rooted in the abnormal multivalent-cation co-intercalation with anions in the form of large-sized anionic complexes. This cation co-intercalation behavior persists throughout the stage evolution of graphite intercalation compounds and leads to a significant decrease of sites practically viable for capacity contribution inside graphite galleries. Further systematic studies illustrate that the phenomenon of cation co-intercalation into graphite is closely related to the high energy penalty of interfacial anion desolvation due to the strong cation-anion association prevalent in multivalent electrolytes. Leveraging this understanding, we verify that promoting ionic dissociation in multivalent electrolytes by employing high-permittivity and oxidation-tolerant co-solvents is effective in suppressing multivalent-cation co-intercalation and thus achieving increased capacity of graphite cathodes. For instance, introducing adiponitrile as a co-solvent to a Mg2+-based carbonate electrolyte leads to 83% less Mg2+ co-intercalation and a ∼29.5% increase in delivered capacity of the graphite cathode.

An oxalato-bridged dimetallic heptanuclear [K5IFe2III] complex anion with guanidinium as counter cation: Synthesis, crystal structure, Hirshfeld surface analysis and magnetism

An oxalato-bridged heterometallic heptanuclear [K5IFe2III] hybrid salt, (CH6N3)[K5(H2O)4Fe2(C2O4)6] (1) (CH6N3+ = guanidinium cation) has been synthesized and characterized by elemental and thermal analyses, IR spectroscopy, single-crystal X-ray diffraction, EPR and SQUID magnetometry. The asymmetric unit in 1 is composed of a dimetallic heptanuclear [K5(H2O)4Fe2(C2O4)6]− anionic complex and a guanidinium CH6N3+ cation insuring the charge compensation. Each Fe3+ center in the anionic complex is six-coordinate in a distorted octahedron defined by three chelating oxalato(2-) ligands. In contrast, the coordination numbers for K+ centers range from 7 to 9. The structural feature of focal interest in 1 is formation of an extended anionic network encapsulating guanidinium cations. This structure can be considered a sheet-MOF, where metal ions and oxalates (linkers) form infinite 2D units. The 3-D supramolecular architecture is stabilized by OH∙∙∙O and NH∙∙∙O hydrogen bonds linking polymeric oxalato-bridged anionic assemblies and organic cations. The thermal studies confirmed the anhydrous character of salt 1 and showed a three-step decomposition to yield a mixture of Fe2O3 and K2O as final residue. EPR spectrum of 1 is in accordance with the oxidation state + 3 of the iron center in an octahedral environment. Temperature-dependence susceptibility measurements investigated in the temperature range 2–300 K revealed weak antiferromagnetic coupling at low temperatures in salt 1. The distributions of different types of intermolecular interactions in the crystal structure were quantified by Hirshfeld surface analysis and their associated fingerprint plots.

Extraction and immediate solidification of uranium (VI) using malonamide functionalized ionic liquids from H2SO4 leaching liquor by specific self-assembly process

A novel self-assembly process for simultaneous extraction and solidification of uranium (VI) from H2SO4 leaching liquor was pioneered using malonamide-based distearyldimethylammonium ionic liquids ([D1821]+[MA]−), which exhibited the good affinity and excellent extraction efficiency for uranium compared to 18 main elements, including Ca, Na, K, Al, Mg, Fe, Cu, Se, Sr, W, Mn, Zn, V, Co, Cr, Ba, Pb and Cd in real leaching liquor. The simultaneous separation and recovery of uranium (VI) was firstly realized by the selective self-assembly extraction of complex anion to form the solid by [D1821]+[MA]−, while leaving the other sulfates in aqueous solution. More than 99 % of uranium(VI) was extracted and enriched as self-assembly solid in one-step process, which could be easily recovered by filtration without further stripping and final precipitation. The self-assembly solid was characterized by XPS, FT-IR, 1H NMR, DLS and SEM-EDS methods. Based on the slope analysis and ESI-HRMS data, an unusual extraction mechanism was proposed in three-step process. [D1821]+[MA·UO2SO4]− was confirmed as the predominant component of self-assembly solid. The maximum loading capacity reached as high as 0.52 mol U(VI) per mole of the ionic liquid. The fewer steps, low cost, high extraction efficiency and excellent selectivity endowed the present strategy with the significant value in uranium hydrometallurgy, which could be employed as a potential alternative for recovery of uranium from real leaching liquor.

Step-by-Step Electrocrystallization Processes to Make Multiblock Magnetic Molecular Heterostructures.

Assembling conductive or magnetic heterostructures by bulk inorganic materials is important for making functional electronic or spintronic devices, such as semiconductive p-doped and n-doped silicon for P-N junction diodes, alternating ferromagnetic and nonmagnetic conductive layers used in giant magnetoresistance (GMR). Nonetheless, there have been few demonstrations of conductive or magnetic heterostructures made by discrete molecules. It is of fundamental interest to prepare and investigate heterostructures based on molecular conductors or molecular magnets, such as single-molecule magnets (SMMs). Herein, we demonstrate the fabrication of a series of molecular heterostructures composed of (TTF)2M(pdms)2 (TTF = tetrathiafulvalene, M = Co(II), Zn(II), Ni(II), H2pdms = 1,2-bis(methanesulfonamido)benzene) multiple building blocks through a well-controlled step-by-step electrocrystallization growth process, where the Co(pdms)2, Ni(pdms)2, and Zn(pdms)2 anionic complex is a SMM, paramagnetic, and diamagnetic molecule, respectively. Magnetic and SMM properties of the heterostructures were characterized and compared to the parentage (TTF)2Co(pdms)2 complex. This study presents the first methodology for creating molecule-based magnetic heterostructural systems by electrocrystallization.

Anion Coordination into Ligand Clefts

A tripodal anion receptor has been obtained by an easy and fast single-reaction synthesis from commercial reagents. The three ligand arms-bearing aromatic groups able to form anion–π interactions define ligand clefts where large anions, such as perchlorate and perrhenate, are included. We report here the synthesis of the ligand, its acid/base properties in an aqueous solution which has been used to direct the synthesis of anion complexes, and the crystal structure of the free ligand and its anion complexes H3L(ClO4)2·H2O and H3L(ReO4)2.

Dramatic reduction of toxicity of Poly(hexamethylene guanidine) disinfectant by charge neutralization

The current study aimed to investigate the toxicity of positively charged polyhexamethylene guanidine (PHMG) polymer and its complexation with different anionic natural polymers such as k-carrageenan (kCG), chondroitin sulfate (CS), sodium alginate (Alg.Na), polystyrene sulfonate sodium (PSS.Na) and hydrolyzed pectin (HP). The physicochemical properties of the synthesized PHMG and its combination with anionic polyelectrolyte complexes (PECs) namely PHMG:PECs were characterized using zeta potential, XPS, FTIR, and TG analysis. Furthermore, cytotoxic behavior of the PHMG and PHMG:PECs, respectively, were evaluated using human liver cancer cell line (HepG2). The study results revealed that the PHMG alone had slightly higher cytotoxicity to the HepG2 cells than the prepared polyelectrolyte complexes such as PHMG:PECs. The PHMG:PECs showed a significant reduction of cytotoxicity to the HepG2 cells than the pristine PHMG alone. A reduction of PHMG toxicity was observed may be due to the facile formation of complexation between the positively charged PHMG and negatively charged anionic natural polymers such as kCG, CS, Alg. Na, PSS.Na and HP, respectively, via charge balance or neutralization. The experimental results indicate that the suggested method might significantly lower PHMG toxicity while improving biocompatibility.

Synthesis and crystal structures of yttrium and dysprosium tetrakis(hexafluoroacetylacetonato) complex anions with tetramethylammonium counterions

The isostructural mononuclear complexes (Et3NH)[M(hfac)4], where M = Y (1) and Dy (2), Hhfac = hexafluoroacetylacetone, have been synthesized and structurally characterized. The two compounds crystalize in monoclinic crystal system (P21/n space group). The purity of the crystalline phases was investigated by X-ray powder diffraction. The analysis of the packing diagram reveals the segregation of the fluorine atoms from the CF3 groups.

Synthesis and Luminescence Properties of Self-Assembled Lanthanide Complexes with an EDTA-Type Chelating Ligand in Aqueous Ethanol Solution

Abstract A hexadentate chelating ligand based on ethylenediaminetetraacetic acid (EDTA) with four cholesteryl groups (L2) was designed and synthesized. L2 forms stable 1:1 complexes with lanthanide ions, and the resulting L2-lanthanide complexes form stable self-assemblies with an average particle size of ∼50 nm in aqueous ethanol solution (20 wt%). Under these conditions, the L2-lanthanide complexes exhibit amphiphilic properties and long-lived luminescence. Sodium 2-naphthoate was added as a guest anion to form a 1:2 complex (anion:Ln) with a lanthanide complex resulting in exciton-coupled circular dichroism spectra. 4-Alkyl benzoates were also used as guest anions, and the intensity of the sensitized luminescence largely depends in this case on the length of their alkyl chain.

Immobilizing Surface Halide in Perovskite Solar Cells via Calix[4]pyrrole.

Halide diffusion across the charge-transporting layer followed by a reaction with metal electrode represents a critical factor limiting the long-term stability of perovskite solar cells (PSCs). In this work, a supramolecular strategy with surface anion complexation is reported for enhancing the light and thermal stability of perovskite films, as well as devices. Calix[4]pyrrole (C[4]P) is demonstrated as a unique anion-binding agent for stabilizing the structure of perovskite by anchoring surface halides, which increases the activation energy for halide migration, thus effectively suppressing the halide-metal electrode reactions. The C[4]P-stabilized perovskite films preserve their initial morphology after ageing at 85°C or under 1 sun illumination in humid air over 50 h, significantly outperforming the control samples. This strategy radically tackles the halide outward-diffusion issue without sacrificing charge extraction. Inverted-structured PSCs based on C[4]P modified formamidinium-cesium perovskite exhibit a champion power conversion efficiency of over 23%. The lifespans of unsealed PSCs are unprecedentedly prolonged from dozens of hours to over 2000 h under operation (ISOS-L-1) and 85°C ageing (ISOS-D-2). When subjected to a harsher protocol of ISOS-L-2 with both light and thermal stresses, the C[4]P-based PSCs maintain 87% of original efficiency after ageing for 500 h.

Assembly of One to Four As4 Analogues, (Ge2 As2 )2- or (Ge3 As)3- , in the Coordination Sphere of [PhM]+ , [MesM]+ , or M2+ (M=Zn, Cd, Hg).

Pseudo-tetrahedral units of p-block atoms proved to be excellent building blocks for novel molecular architectures and for introducing new elemental combinations which are not otherwise accessible. In this work, we present a series of clusters obtained by reactions of binary Ge/As anions with [MPh2 ] (M=Zn, Cd, Hg; Ph=phenyl). The study is grounded on the fact that the binary reactant gained by extracting the solid 'K2 GeAs' with ethane-1,2-diamine (en) co-exists as (Ge2 As2 )2- and (Ge3 As)3- in solution. This allows for a larger variety of products by 'selecting' the most suitable species for the final ternary complex to crystallize. The reactions afforded the unprecedented first step of the corresponding interaction, thus attachment of (MPh)+ to a pseudo-tetrahedral unit in [PhZn(Ge3 As)]2- (1) and [PhHg(Ge3 As)]2- (2), and complex anions with two, three, or four units, [(Ge3 As)Zn(Ge2 As2 )]3- (3), [Cd3 (Ge3 As)3 ]3- (4), and [Zn3 (Ge3 As)4 ]6- (5). Quantum chemistry confirmed the compositions and the positions of the Ge or As atoms, beside explaining structural peculiarities. The subtle impact of different [MR2 ] reactants was additionally studied by corresponding reactions using [ZnMes2 ] (Mes=mesityl), which showed success in selectively crystallizing [MesZn(Ge3 As)]2- (6). Based on our findings, we derive a suggestion of the underlying reaction cascade.

Assembly of One to Four As4 Analogues, (Ge2As2)2− or (Ge3As)3−, in the Coordination Sphere of [PhM]+, [MesM]+, or M2+ (M=Zn, Cd, Hg)

AbstractPseudo‐tetrahedral units of p‐block atoms proved to be excellent building blocks for novel molecular architectures and for introducing new elemental combinations which are not otherwise accessible. In this work, we present a series of clusters obtained by reactions of binary Ge/As anions with [MPh2] (M=Zn, Cd, Hg; Ph=phenyl). The study is grounded on the fact that the binary reactant gained by extracting the solid ‘K2GeAs’ with ethane‐1,2‐diamine (en) co‐exists as (Ge2As2)2− and (Ge3As)3− in solution. This allows for a larger variety of products by ‘selecting’ the most suitable species for the final ternary complex to crystallize. The reactions afforded the unprecedented first step of the corresponding interaction, thus attachment of (MPh)+ to a pseudo‐tetrahedral unit in [PhZn(Ge3As)]2− (1) and [PhHg(Ge3As)]2− (2), and complex anions with two, three, or four units, [(Ge3As)Zn(Ge2As2)]3− (3), [Cd3(Ge3As)3]3− (4), and [Zn3(Ge3As)4]6− (5). Quantum chemistry confirmed the compositions and the positions of the Ge or As atoms, beside explaining structural peculiarities. The subtle impact of different [MR2] reactants was additionally studied by corresponding reactions using [ZnMes2] (Mes=mesityl), which showed success in selectively crystallizing [MesZn(Ge3As)]2− (6). Based on our findings, we derive a suggestion of the underlying reaction cascade.

Frontispiece: Square‐Planar Anionic Pt0 Complexes

Coordination Compounds. A diphosphine-borane ligand (DPB) enables the straightforward synthesis of unique examples of square-planar anionic Pt0 complexes [(DPB)PtX]−, as reported by Hajime Kameo, Didier Bourissou et al. in their Communication (e202301509).

Frontispiz: Square‐Planar Anionic Pt0 Complexes

Coordination Compounds. A diphosphine-borane ligand (DPB) enables the straightforward synthesis of unique examples of square-planar anionic Pt0 complexes [(DPB)PtX]−, as reported by Hajime Kameo, Didier Bourissou et al. in their Communication (e202301509).

Monovalent Thulium. Synthesis and Properties of TmI

The reaction of thulium shavings with iodine at 680°C gave a poorly separable product mixture A, consisting of thulium metal (65%), TmI2 (14%), and TmI (21%). Monovalent thulium iodide could not be isolated in a pure state, but its presence among the products was confirmed, apart from magnetic measurements, by reactions with naphthalene and perylene, which proceed under mild conditions. The reaction of TmI with naphthalene, which takes place at –40°C, affords the trivalent thulium complex with naphthalene dianion, [TmI(C10H8)(DME)3]. The multistep reaction with perylene starts with the formation of the divalent thulium radical anion complex, [(TmI)+(C20H12)–•(DME)3], and ends in the formation of trivalent thulium complex, [(TmI)2+(C20H12)2–(DME)3]. The presence of a radical anion intermediate in the reaction mixture in an early stage was confirmed by ESR spectroscopy.