Alkali Metal Cations Research Articles

Formamidinium Incorporates into Rb-based Non-Perovskite Phases in Solar Cell Formulations.

Organic-inorganic hybrid perovskite materials, such as formamidinium lead iodide (FAPbI3), are among the most promising emerging photovoltaic materials. However, the spontaneous phase transition from the photoactive perovskite phase to an inactive non-perovskite phase complicates the application of FAPbI3 in solar cells. To remedy this, alkali metal cations, most often Cs+, Rb+ or K+, are included during perovskite synthesis to stabilize the photoactive phase. The atomic-level mechanisms of stabilization are complex. While Cs+ dopes directly into the perovskite lattice, Rb+ does not, but instead forms an additional non-perovskite phase, and the mechanism by which Rb confers increased stability remains unclear. Here, we use 1H-87Rb double resonance NMR experiments to show that FA+ incorporates into the Rb-based non-perovskite phases (FAyRb1-yPb2Br5 and δ-FAyRb1-yPbI3) for both bromide and iodide perovskite formulations. This is demonstrated by changes in the 1H and 87Rb chemical shifts, 1H-87Rb heteronuclear correlation spectra, and 87Rb{1H} REDOR spectra. Simulation of the REDOR dephasing curves suggests up to ~60 % FA+ incorporation into the inorganic Rb-based phase for the bromide system. In light of these results, we hypothesize that the substitution of FA+ into the non-perovskite phase may contribute to the greater stability conferred by Rb salts in the synthesis of FA-based perovskites.

Formamidinium Incorporates into Rb‐based Non‐Perovskite Phases in Solar Cell Formulations

AbstractOrganic‐inorganic hybrid perovskite materials, such as formamidinium lead iodide (FAPbI3), are among the most promising emerging photovoltaic materials. However, the spontaneous phase transition from the photoactive perovskite phase to an inactive non‐perovskite phase complicates the application of FAPbI3 in solar cells. To remedy this, alkali metal cations, most often Cs+, Rb+ or K+, are included during perovskite synthesis to stabilize the photoactive phase. The atomic‐level mechanisms of stabilization are complex. While Cs+ dopes directly into the perovskite lattice, Rb+ does not, but instead forms an additional non‐perovskite phase, and the mechanism by which Rb confers increased stability remains unclear. Here, we use 1H−87Rb double resonance NMR experiments to show that FA+ incorporates into the Rb‐based non‐perovskite phases (FAyRb1‐yPb2Br5 and δ‐FAyRb1‐yPbI3) for both bromide and iodide perovskite formulations. This is demonstrated by changes in the 1H and 87Rb chemical shifts, 1H−87Rb heteronuclear correlation spectra, and 87Rb{1H} REDOR spectra. Simulation of the REDOR dephasing curves suggests up to ~60 % FA+ incorporation into the inorganic Rb‐based phase for the bromide system. In light of these results, we hypothesize that the substitution of FA+ into the non‐perovskite phase may contribute to the greater stability conferred by Rb salts in the synthesis of FA‐based perovskites.

Synergistic Regulation of DNA Morphology by Metal Cations and Low pH.

As a flexible biomolecule, the spatial structure of DNA is variable. The effects of concentration, metal cations, and low pH on DNA morphology were studied. For the high concentration of DNA, the cross-linked branch-like or network structures were formed. For the low concentration of DNA, isolated, random and freely loose linear DNA chains were presented. These phenomena were related to the intermolecular interactions. Branch-like DNA structures were reformed with the addition of metal cations to the low concentration of DNA at pH 7-4, suggesting the negative charges of DNA were neutralized, thus transforming the spatial structure of DNA into a low charge density morphology and presenting the hypochromic effect. Compared to the monovalent alkaline metal cations, more negative charges of DNA were screened by the alkaline-earth metal cations. Distinct DNA morphologies were observed for pH 3. The linear and condensed DNA structures were simultaneously observed, which was met regardless of the solution with or without the addition of metal cations. This was further confirmed by the absorbance of DNA. Compared to the pure DNA, bulky and aggregated DNA collapsed structures were formed when the sodium and magnesium cations were added to the reaction solution. In addition, it was verified that the condensed DNA structures failed to revert back to the chain structure by neutralizing acidic solutions with alkali, but the compacted DNA spheres became loose. The conductivities of various DNA morphologies were measured. They were morphology-dependent. This study provides guidance forthe behavior of DNA in the acidic solutions and further promotes the application of DNA in DNA-based nano-optoelectronic devices.

Deciphering Doping Effects in a V-Doped Ni Catalyst for Hydrogen Electrooxidation.

The improved performance of soluble metal-doped Ni catalysts is perplexed by the evolvable surface structures in the alkaline electrolytes for hydrogen oxidation reaction (HOR). Herein, V-doped Ni nanoparticles, as a proof of concept, were carefully evaluated to explore the intrinsic function of the enthetic V-species in assisting the HOR kinetic improvement. As expected, it exhibits a mass-normalized kinetic current density of 50.34 mA mgNi-1, more than 12 times that of the Ni counterpart without the introduction of V. Systematic investigations prove that the surface V-species, including the V-oxides and the doped V atoms at the outmost layer, would be dissolved into the electrolytes during the alkaline HOR process. The remaining V-dopants inside the nanoparticles would rationally weaken the hydroxyl binding energy (OHBE) of the Ni-based surfaces, thereby accelerating the formation of water molecules. We also uncover that Ni is located at the overstrong branch of the OHBE-described volcano plot through theoretical calculations and alkali-metal cation probe experiments, and weakening the OHBE by internal V-doping can leave the activity to the volcanic apex.

Pb2TeV2O10: A Lead Vanadate Tellurate with Wide Mid-IR Transparency and Large Birefringence Induced by Multiple Birefringence-Active Groups.

Birefringent materials as the key materials in laser science and technology have attracted continuous attention due to their ability to modulate polarized light. Herein, a new lead vanadate tellurate, Pb2TeV2O10, has been synthesized through the rational integration of different kinds of birefringence-active functional units. Pb2TeV2O10 features a unique two-dimensional (2D) [TeV2O10]∞ layered structure consisting of [VO6]7- and [TeO6]6- octahedra, and Pb2+ cations reside between the [TeV2O10]∞ layers. In addition, the rare edge-sharing mode of [VO6]7- and [TeO6]6- octahedra was found in this structure. Attributed to the high polarizability and appropriate arrangement of PbO8, VO6, and TeO6 units, Pb2TeV2O10 possesses a great theoretical birefringence of 0.275 at 532 nm, which is the largest among the vanadate tellurate family. The spectral tests also prove that Pb2TeV2O10 showcases a broad transparency window (439 nm-10 μm), covering an important mid-infrared (IR) atmospheric window (3-5 μm). In addition, in order to improve the transparency, alkali and alkaline earth metal cations were introduced by the substitution strategy, and then the compound K2Sr2Te2O9 was synthesized. It owns a shorter ultraviolet (UV) cutoff edge of 234 nm and a wider transparency window (234 nm-13.8 μm). The findings of Pb2TeV2O10 and K2Sr2Te2O9 enrich the structure chemistry of the tellurate family and provide new insights for designing new compounds with large optical anisotropy and wide spectral transparency.

Alkali metal cations at work: Enhancing CO2 electroreduction to CO on ZnO nanorods

Oxide-derived zinc, an abundant and cost-effective electrode material alternative to gold and silver, has exhibited high activity for the electroreduction of CO2 to CO (CO2RR). However, the impact of cations on the CO2RR activity remains unexplored. In this study, we investigated the effect of three alkali metal cations (Cs+, K+, and Li+) on the CO2RR over a ZnO nanorod electrode, using a rotating ring disk electrode (RRDE) technique. Cyclic voltammetry of the Pt ring in the RRDE tip reveals a consistent trend in the buffering capacity of these cations (Cs+ > K+ > Li+), as evidenced by the availability of OH⁻ ions for CO electrooxidation and hydrogen oxidation reactions (HOR). Cs+ showed a pronounced effect on the activity of the CO2RR to CO since it can regulate OH⁻ concentration and maintain the local pH. This study addresses the ongoing debate concerning the effects of cations; interfacial electric field and buffering capacity; and elucidates the relationship among electrolyte/cation, local pH dynamics, and the CO2RR activity towards CO over the active oxide-derived Zn electrodes, all derived from the fast and facile RRDE technique.

Alkali metal cation adsorption–induced surface polarization in polymeric carbon nitride for enhanced photocatalytic hydrogen peroxide production

Photocatalytic hydrogen peroxide (H2O2) generation on the catalyst surface from oxygen is an electron-demanding process, making the construction of an electron-rich surface highly advantageous. In this study, a localized electric field was observed on the surface of polymeric carbon nitride (g-C3N4) when alkali metal cations were adsorbed onto it. These fields effectively inhibited surface carrier recombination and extended their lifespan, thereby enhancing H2O2 production. As a result, g-C3N4 achieved a superior H2O2 yield of 2.25 mM after 1 h in a 0.25 M K+ solution, which was 2.06 times greater than that (1.09 mM) achieved in a pure solvent. Notably, the increase in photocatalytic efficiency showed a remarkable dependence on ion species. At low concentrations, H2O2 generation efficiency was in the order of Li+ < Na+ < K+ < Rb+ < Cs+. However, after optimizing the ion concentration, the highest H2O2 production was achieved in a solution containing K+ instead of Cs+. Molecular dynamics simulations and temperature-dependent photocatalysis experiments revealed that the synergistic interaction between adsorption energy and adsorption distance was crucial in governing the extent to which alkali metal cation adsorption enhanced g-C3N4 photocatalytic H2O2 production. This study provides theoretical insights for the design of materials for electron-demanding photocatalysis and aids in understanding variations in photocatalytic behavior in natural waters.

Mitigating anodic corrosion in aluminum–air batteries: Effects of alkali metal cation size on electrochemical performance

Anodic corrosion limits the performance of aluminum–air batteries (AABs) by reducing discharge capacity and hindering energy density. This study proposes a strategy to mitigate anodic corrosion by controlling electrolyte cations to decrease the activity of free water molecules in the anodic corrosion process. Alkali metal cations (Na+, K+, Rb+) are introduced into a 1mol dm−3 KOH solution to examine their solvation properties and effects on free water molecule activity. Results show that larger cations (Na+ < K+ < Rb+) enhance anode discharge capacity by promoting more stable discharge reactions. Raman spectroscopy reveals that as cation radius increases, free water molecule activity decreases due to increased hydration. X-ray photoelectron spectroscopy analysis shows that larger cations favor the formation of corrosion-resistant aluminum compounds like Al2O3 and Al(OH)3, due to their higher concentration in the electric double layer, inhibiting anodic corrosion. This study highlights the critical role of cation solvation in enhancing electrochemical performance and corrosion resistance of AAB anodes.

Modulating the structural and electrical properties of SrFeO3–δ by a-site alkali metal ion doping

The electrical properties of perovskite structured SrFeO3–δ can be modulated by A site doping. The present work focuses on the influence of concentration and ionic radii of alkali metal cation on the structural and electrical properties of Sr1–xAxFeO3–δ (A = Ca, Ba and x = 0, 0.25, 0.50, 0.75). The x-ray diffraction studies confirm the phase change from cubic to orthorhombic with Ca content while orthorhombic to cubic structural translation was observed with Ba concentration. A lattice contraction and expansion were observed for doping depending on the ionic radii of dopant cation. The x-ray photoelectron spectroscopy results indicate the presence of Fe in mixed valence state of +2, +3, +4 state and adsorbed oxygen content was found to be higher upon Ba doping than that of Ca. A maximum conductivity of 1.82 × 10−3 S cm−1 (x = 0.25) and 5.31 × 10−3 S cm−1 (x = 0.5) was observed at 800 °C for Ca and Ba doped samples, respectively, one order higher than the base SrFeO3–δ .Thus, our results emphasise the importance of dopant addition on tailoring the electrode properties for SOFC application.

Alkali Metal Cations Induce Structural Evolution on Au(111) During Cathodic Polarization.

The activity of the electrocatalytic CO2 reduction reaction (CO2RR) is substantially affected by alkali metal cations (AM+) in electrolytes, yet the underlying mechanism is still controversial. Here, we employed electrochemical scanning tunneling microscopy and in situ observed Au(111) surface roughening in AM+ electrolytes during cathodic polarization. The roughened surface is highly active for catalyzing the CO2RR due to the formation of surface low-coordinated Au atoms. The critical potential for surface roughening follows the order Cs+ > Rb+ > K+ > Na+ > Li+, and the surface proportion of roughened area decreases in the order of Cs+ > Rb+ > K+ > Na+ > Li+. Electrochemical CO2RR measurements demonstrate that the catalytic activity strongly correlates with the surface roughness. Furthermore, we found that AM+ is critical for surface roughening to occur. The results unveil the unrecognized effect of AM+ on the surface structural evolution and elucidate that the AM+-induced formation of surface high-activity sites contributes to the enhanced CO2RR in large AM+ electrolytes.

High rate capability and ultra‐long cycling life: Electrochemical synthesis of PEDOT based electrode material doped with AMPS and its supercapacitor application

AbstractPoly(3,4‐ethylene dioxythiophene) (PEDOT) is a conducting polymer that can be used in flexible bioelectronic devices. The electrode/electrolyte interface interaction is one of the most important factors in improving the electrochemical performance of energy storage materials, and these polymers are often combined with a negatively charged poly(styrene sulfonate) (PSS) chain to improve their interaction with alkali metal cations such as sodium and potassium. In this work, we performed a one‐step electrochemical synthesis of PEDOT on carbon fabric using the molecule 2‐acrylamido‐2‐methyl‐1‐propane sulfonic acid (AMPS) to create highly effective materials for supercapacitor electrodes. The electrode had a significant increase in capacitance value, measured 16.4 times higher than that of the PEDOT electrode. The 2‐electrode system exhibited a specific capacitance value of 495.2 F g−1 at a scan rate of 5 mV s−1. It exhibited a high operating voltage of 2.3 V in aqueous electrolyte system. It showed a significant energy density of 109.0 Wh kg−1 when operating at 6.1 kW kg−1 power density and 85.2 Wh kg−1 when operating at 30.6 kW kg−1 power density. Recent findings reveal that the capacitance retention performance value of the device increased significantly to 113.9% after 25,000 cycles in 3.0 M NaCl aqueous electrolyte, demonstrating its outstanding long‐term durability. Thus, the creation of the synthesized supercapacitor electrode is a significant advance in the study of conducting polymers, which often have a limited lifetime in real‐world electronic applications.

Ethanol Oxidation Reaction on Electrodeposited Pd and Sb‒Pd Catalysts in Alkaline Solution Containing Na or Li Cations

Abstract This work reports the galvanostatical electrodeposition of Pd and Sb‒Pd catalysts on rotating glassy carbon (GC) electrode using surfactant-free electrolytes and the prepared catalysts were tested is the electro-oxidation reactions in alkaline solutions. Characterization of Pd and Sb‒Pd catalysts was performed with scanning electron microscope (SEM), energy-dispersive X-ray spectroscopy (EDS) and X-ray photoelectron spectroscopy (XPS) technique. Cyclic voltammetry (CV) and chronoamperometry were applied in order to study the electrocatalytic behavior of Pd and Sb‒Pd catalysts in the ethanol oxidation reaction (EOR) in alkaline solution containing Na+ or Li+ cations from the point of the impact of the selected alkali metal cations on the electrocatalytic activity. The peak current of EOR at Pd and Sb‒Pd catalysts in the solution with Li+ cations is 2.5 times higher compared to the values obtained in the solution with Na+ cations. EOR starts at rather negative potentials in LiOH solution regarding NaOH for approximately 0.03 V indicating the active role of OHad and the impact of the nature of alkali metal cations which consequently arises from the formation of OHad ‒ cation clusters. The role of Sb in bimetallic catalyst was established by adjusting the extent and persistence of OHad surface coverage.

1D Anionic Covalent Organic Frameworks With Directed Migration of Alkali Metal Ions for High Ionic Conductivity.

Rational construction of high-performance ionic conductors is a critical challenge in the field of energy storage. In this study, a series of 1D anionic titanium-based covalent organic frameworks (COFs) containing abundant alkali metal ion migration sites, namely, COF-M-R (M = Li, Na, K; R = H, Me, Et), is constructed. The integration of negative TiO6 2- sites on 1D anionic COFs allows alkali metal cations to migrate directly through the channels. Meanwhile, the π-π stacking of 1D chain-to-chain allows the distribution of ion-migration sites in 2D planes. In view of this, multidimensional ionic transport in COFs is realized to achieve high ionic conductivity. COF-M-Rs exhibit an increased ionic conductivity as the counterions change from Li+ to Na+ to K+. Notably, COF-Na-Et has an impressive ionic conductivity as high as 0.81 × 10-3 S cm-1. The different decorated groups (H, Me, and Et) on the skeleton influence the dissociation of the cation from the polyanion. This study offers deep insights into the design of COF-based solid-state electrolytes to achieve high ionic conductivity by increasing the ionic transport dimensions.

A Solid-State Electrolyte Facilitates Acidic CO2 Electrolysis without Alkali Metal Cations by Regulating Proton Transport.

Electrochemical CO2 reduction (CO2R) in acidic media provides a pathway to curtail CO2 losses by suppressing the formation of (bi)carbonates. In such systems, a high concentration of alkali metal cations is necessary for mitigating the proton-rich environment and suppressing the competing hydrogen evolution reaction. However, a high cation concentration also promotes salt precipitation within the gas diffusion layer, resulting in poor system durability. Here, we resolve this conundrum by replacing the liquid catholyte with a solid-state proton conductor to regulate H+ transport. This is postulated to allow for a locally alkaline environment at the cathode, enabling selective CO2R even without alkali metal cations. We show that this strategy is effective over a broad range of catalyst systems. For instance, we achieve an 87% CO faradaic efficiency (FE) at 300 mA/cm2 using a composite nanoporous Au and single-atom Ni catalyst, with 0.25 M H2SO4 as the anolyte. Stable operation over 110 h and a high single-pass carbon efficiency of 82.8% were also successfully demonstrated. Importantly, we find that this solid-state system is also particularly effective at converting dilute feedstock (5% CO2) with a CO FE of 47.7%, a factor of 16.4 times higher than a conventional system. Our results introduce a simple yet effective design approach for developing efficient acidic CO2R electrolyzers.

Effect of ion-specific water structures at metal surfaces on hydrogen production

Water structures at electrolyte/electrode interfaces play a crucial role in determining the selectivity and kinetics of electrochemical reactions. Despite extensive experimental and theoretical efforts, atomic-level details of ion-specific water structures on metal surfaces remain unclear. Here we show, using scanning tunneling microscopy and noncontact atomic force microscopy, that we can visualize water layers containing alkali metal cations on a charged Au(111) surface with atomic resolution. Our results reveal that Li+ cations are elevated from the surface, facilitating the formation of an ice-like water layer between the Li+ cations and the surface. In contrast, K+ and Cs+ cations are in direct contact with the surface. We observe that the water network structure transitions from a hexagonal arrangement with Li+ to a distorted hydrogen-bonding configuration with Cs+. These observations are consistent with surface-enhanced infrared absorption spectroscopy data and suggest that alkali metal cations significantly impact hydrogen evolution reaction kinetics and efficiency. Our findings provide insights into ion-specific water structures on metal surfaces and underscore the critical role of spectator ions in electrochemical processes.

Gas-Phase Structures of Fucosylated Oligosaccharides: Alkali Metal and Halogen Influences.

Fucosylated carbohydrate antigens play critical roles in physiology and pathology with function linked to their structural details. However, the separation and structural characterization of isomeric fucosylated epitopes remain challenging analytically. Here, we report for the first time the influence of alkali metal cations (Li+, Na+, K+, Rb+, and Cs+) and halogen anions (Cl-, Br-, and I-) on the gas-phase conformational landscapes of common fucosylated trisaccharides (Lewis A, X, and H types 1 and 2) and tetrasaccharides (Lewis B and Y) using trapped ion mobility spectrometry coupled to mass spectrometry and theoretical calculations. Inspection of the mobility profiles of individual standards showed a dependence on the number of mobility bands with the oligosaccharide and the alkali metal and halogen; collision cross sections are reported for all of the observed species. Results showed that trisaccharides (Lewis A, X, and H types 1 and 2) can be best mobility resolved in the positive mode using the [M + Li]+ molecular ion form (baseline resolution r ≈ 2.88 between Lewis X and A); tetrasaccharides can be best mobility resolved in the negative mode using the [M + I]- molecular ion form (baseline separation r ≈ 1.35 between Lewis B and Y). The correlation between the number of oligosaccharide conformers as a function of the molecular ion adduct was studied using density functional theory. Theoretical calculations revealed that smaller cations can form more stable structures based on the number of coordinations, while larger cations induced greater oligosaccharide reorganizations; candidate structures are proposed to better understand the gas-phase oligosaccharide rearrangement trends. Inspection of the candidate structures suggests that the interplay between ion size/charge density and molecular structure dictated the conformational preferences and, consequently, the number of mobility bands and the mobility separation across isomers. This work provides a fundamental understanding of the gas-phase structural dynamics of fucosylated oligosaccharides and their interaction with alkali metals and halogens.

Elucidating the Role of Alkali Metal Carbonates in Impact on Oxygen Vacancies for Efficient and Stable Perovskite Solar Cells.

Effectively suppressing nonradiative recombination at the SnO2/perovskite interface is imperative for perovskite solar cells. Although the capabilities of alkali salts at the SnO2/perovskite interface have been acknowledged, the effects and optimal selection of alkali metal cations remain poorly understood. Herein, a novel approach for obtaining the optimal alkali metal cation (A-cation) at the interface is investigated by comparatively analyzing different alkali carbonates (A2CO3; Li2CO3, Na2CO3, K2CO3, Rb2CO3, and Cs2CO3). Theoretical calculations demonstrate that A2CO3 coordinates with undercoordinated Sn and O on the surface, effectively mitigating oxygen vacancy (VO) defects with increasing A-cation size, whereas Cs2CO3 exhibits diminished preferability owing to enhanced steric hindrance. The experimental results highlight the crucial role of Rb2CO3 in actively passivating VO defects, forming a robust bond with SnO2, and facilitating Rb+ diffusion into the perovskite layer, thereby enhancing charge extraction, alleviating deep-level trap states and structural distortion in the perovskite film, and significantly suppressing nonradiative recombination. X-ray absorption spectroscopy analyses further reveal the effect of Rb2CO3 on the local structure of the perovskite film. Consequently, a Rb2CO3-treated device with aperture area of 0.14 cm2 achieves a notable efficiency of 22.10%, showing improved stability compared to the 20.11% achieved for the control device.

Electrochemical and surface characterisation of poly(3,4-ethylenedioxythiophene) dodecylbenzenesulfonate layers

Poly(3,4-ethylenedioxythiophene) (PEDOT) films were electrochemically synthesised with sodium dodecylbenzenesulfonate (DBS) and chloride acting as dopant anions within the polymer matrix. Upon redox switching of the PEDOT/DBS film between conducting and non-conducting states, the DBS anion remained within the polymer and cation insertion and expulsion occurred, as confirmed by Electrochemical Quartz Crystal Microbalance (EQCM) measurements. Electrolytes composed of alkali metal cations of varying masses (Li+, Na+, K+) were employed to investigate the cation insertion/expulsion processes, thereby resulting in varying mass changes being observed upon film redox switching. The charging and discharging of bulky anion doped polymer films presented higher capacitance upon charging and lower capacitance when discharging, which is expected during doping and de-doping as confirmed by AC impedance. In this work, the main results obtained by chemical-physical characterisation are presented and critically discussed, with regard to the possible use of a viable conducting polymer as a drug delivery vehicle.

Lanthanide (Sm, Dy) Complexes with the 9,10-Phenanthrenediimine Redox-Active Ligand: Synthesis and Structures

The complex formation of the redox-active ligand bis(N, N’-2,6-diisopropylphenyl)-9,10-phenanthrenediimine (DippPDI) with alkaline metal (Li, K) and lanthanide (Sm, Dy) cations is studied. The reduction of DippPDI with an alkaline metal excess affords the dianionic form of the ligand (DippPDA2–), which crystallizes with the potassium cation as the coordination polymer [K2(DippPDA)(Thf)3] (Thf is tetrahydrofuran, THF). The reaction of equimolar amounts of the lithium salt with the dianionic form of the ligand and neutral diimine affords the lithium complex with the radical-anion form (DippPSI•–) crystallized as [Li(DippPSI)(Thf)2]. The samarium(III) complex [SmCp*(DippPDA)(Тhf)] (I) is formed by the reduction ofDippPDI with samarocene [Sm (Thf)2] (Cp* is pentamethylcyclopentadienide): both the samarium(II) cation and Cp*– anion are oxidized in the reaction.DippPDI does not react with similar ytterbocene. The dysprosium(III) complexes are synthesized by the ion exchange reactions between DyI3(Thf)3.5 and potassium or lithium salt with theDippPDA2-dianion. Similar complexes [Dy(DippPDA)I(Thf)2] (IIThf) and [Dy(DippPDA)I(Thf)(Et2O)] () are formed in the reactions with the potassium salt depending on the solvent used: a THF-hexane or a diethyl ether-n-hexane mixture, respectively. The coordination of the dysprosium cation by the π system of the conjugated fragment of the NCCN ligand is observed in IIThf, whereas in this coordination is absent. The reaction with Li2(DippPDA) affords the binary complex salt [Li(Тhf)3(Et2O)][DyI2(DippPDA)(Тhf)] (III, crystallization from a THF-Et2O mixture). The crystallization from THF gives the [Li(Тhf)4][DyI2(DippPDA)(Thf)] salt (III') containing the same anion as III. The structures of all new complexes are studied by X-ray diffraction (XRD, CIF files CCDC nos. 2260307–2260313).

Structures and unimolecular chemistry of alkali metal cation complexes with glutathione in the gas phase

This study investigates the unimolecular reactions of glutathione complexes with alkali metal cations in the gas phase through sustained off-resonance irradiation collision-induced dissociation and examines their structures using a combination of infrared multiphoton dissociation spectroscopy and computational techniques. Under soft CID conditions, glutathione complexes with charge-dense cations such as Li⁺, Na⁺, and K⁺ show significant fragmentation of glutathione, while complexes with heavier cations, Rb⁺ and Cs⁺, primarily undergo loss of glutathione. This behavior is attributed to the stronger non-covalent binding between smaller metal cations and glutathione, which competes with the dissociation thresholds of covalent interactions within the peptide complex. Using CREST, a tool for determining trial structures which were submitted to density functional theory calculations, a thorough investigation of the conformational space revealed many possible structures, including pentacoordinated structures for the Na⁺ and K⁺ complexes, as well as tetra-tri-, bi-, and monocoordinated structures along with zwitterionic structures for all metal cation/GSH complexes. For all alkali metal cation complexes, the thermodynamically most stable structures were found to be tetracoordinated A-type structures where the metal cation is bound to the amine nitrogen and three of the carbonyl oxygens—all except O2, the amide between glycine and cysteine. These computed infrared spectra for these lowest energy complexes were also consistent with the experimental vibrational spectra in the fingerprint region. Based on relative energies and the comparison of computed and experimental infrared spectra in the fingerprint region, the tetracoordinate A-type structures are concluded to be the dominant forms of the [M(GSH)]+ complexes in the gas phase.