Size Of Alkali Metal Cation Research Articles

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.

Infrared multiple-photon dissociation spectroscopy of cationized glycine: effects of alkali metal cation size on gas-phase conformation.

The gas-phase structures of cationized glycine (Gly), including complexes with Li+, Na+, K+, Rb+, and Cs+, are examined using infrared multiple-photon dissociation (IRMPD) spectroscopy utilizing light generated by a free electron laser, in conjunction with ab initio calculations. To identify the structures present in the experimental studies, measured IRMPD spectra are compared to spectra calculated at B3LYP/6-311+G(d,p) for the Li+, Na+, and K+ complexes and at B3LYP/def2TZVP for the Rb+ and Cs+ complexes. Single-point energy calculations were carried out at the B3LYP, B3P86, and MP2(full) levels using the 6-311+G(2d,2p) basis set for Li+, Na+, K+ and the def2TZVPP basis set for Rb+ and Cs+. The Li+ and Na+ complexes are identified as metal cation coordination to the amino nitrogen and carbonyl oxygen, [N,CO]-tt, although Na+(Gly) may have contributions from additional structures. The heavier metal cations coordinate to either the carbonyl oxygen, [CO]-cc, or the carbonyl oxygen and hydroxy oxygen, [CO,OH]-cc, with the former apparently preferred for Rb+ and Cs+ and the latter for K+. These two structures reside in a double-well potential and different levels of theory predict very different relative stabilities. Some experimental evidence is provided that MP2(full) theory provides the most accurate relative energies.

Understanding alkali metal cation affinities of multi-layer guanine quadruplex DNA.

To gain better understanding of the stabilizing interactions between metal ions and DNA quadruplexes, dispersion-corrected density functional theory (DFT-D) based calculations were performed on double-, triple- and four-layer guanine tetrads interacting with alkali metal cations. All computations were performed in aqueous solution that mimics artificial supramolecular conditions where guanine bases assemble into stacked quartets as well as biological environments in which telomeric quadruplexes are formed. To facilitate the computations on these significant larger systems, optimization of the DFT description was performed first by evaluating the performance of partial reduced basis sets. Analysis of the stabilizing interactions between alkali cations and the DNA bases in double and triple-layer guanine quadruplex DNA reproduced the experimental affinity trend of the order Li+< Rb+ < Na+ < K+. The desolvation and the size of alkali metal cations are thought to be responsible for the order of affinity. Nevertheless, for the alkali metal cation species individually, the magnitude of the bond energy stays equal for binding as first, second or third cation in double, triple and four-layer guanine quadruplexes, respectively. This is the result of an interplay between a decreasingly stabilizing interaction energy and increasingly stabilizing solvation effects, along the consecutive binding events. This diminished interaction energy is the result of destabilizing electrostatic repulsion between the hosted alkali metal cations. This work emphasizes the stabilizing effect of aqueous solvent on large highly charged biomolecules.

Hysteresis analysis in dye-sensitized solar cell based on different metal alkali cations in the electrolyte

Hysteresis phenomenon occurs in solar cells and its cause is still an arguable issue as it redefines how accurately we control the device performance. Here, the hysteresis behavior in Dye-sensitized solar cell (DSSC) is studied based on the electrolyte. Three electrolytes were used containing Sodium iodide (NaI), Potassium iodide (KI), and Cesium iodide (CsI). Current density-voltage characteristics was measured for each device at fast (1 V/s) scan rate, medium (0.5 V/s) scan rate, and slow (0.1 V/s) scan rate. The charging-discharging process at TiO2/electrolyte interface during forward and reverse scan directions is propose as the responsible mechanism for hysteresis in DSSC. Based on our investigation, hysteresis phenomenon is strongly dependent on the size of alkali metal cation as well as J-V sweep scan rate. Hysteresis is dominant for NaI electrolyte with the smallest Na+ cation size while it diminishes for KI and CsI electrolytes with bigger K+ and Cs+ sizes, respectively. Also, using CsI electrolyte along with the slow scan rate of 0.1 V/s is the perfect combination for the minimal hysteresis in the solar cell. In addition, hysteresis index calculation was redefined based on the intercept cross points between forward and reverse scan directions. Our results suggest that DSSC has a charge storage efficiency accompanied by its primary function as a power conversion device. The charge storage ability occurs for V > VOC during the forward scan and it is significant for smaller cation size.

Single-Crystal Synthesis and Structures of Rb-Boroleucite Rb(BSi2)O6 and Boropollucite Cs(BSi2)O6 at 293 and 120 K

The structures of Rb-boroleucite Rb1.0(B0.333Si0.667)3O6 and boropollucite Cs0.87(B0.290Si0.710)3O6 were studied using single crystals, which were prepared under hydrothermal conditions. In the zeolite-like framework structures, Rb and Cs atoms are located in large window cavities formed by four, six, and eight tetrahedra. The B and Si atom randomly occupy general positions. Cubic space groups of both phases (acentric sp. gr. I $$\bar {4}$$ 3d for Rb and centrosymmetric holohedral sp. gr. Ia $$\bar {3}$$ d for Cs) remain unchanged at room temperature and down to 120 K. Rubidium boroleucite has a stoichiometric formula. Boropollucite is characterized by a deviation from the stoichiometric composition, which is manifested in the predominance of Si atoms in tetrahedra and the defect occupation of the Cs site. The size of alkali metal cations plays a crucial role in the existence of a particular modification, which is consistent with earlier results.

Organic-Free Synthesis of Silicoaluminophosphate Molecular Sieves.

Silicoaluminophosphate (SAPO) molecular sieves are an important class of microporous materials and are useful for industrial catalysis and separations. They have been synthesized exclusively by the use of expensive and environmentally unfriendly organic structure-directing agents. Now the synthesis of SAPO molecular sieves is reported with MER, EDI, GIS, and ANA topologies under wholly inorganic conditions. Multinuclear MAS NMR analyses demonstrate the presence of Si, Al, and P atoms in their frameworks. These SAPO materials all have unusually high framework charge densities (0.25-0.46), owing to the small size of alkali metal cations used as an inorganic structure-directing agent. A continuous Si increase in the synthesis gel for MER-type SAPO molecular sieves led to the formation of framework Si(0Al) units, decreasing the number of extra-framework cations per unit cell and thus making the resulting solid useful for CO2 adsorption.

Organic‐Free Synthesis of Silicoaluminophosphate Molecular Sieves

AbstractSilicoaluminophosphate (SAPO) molecular sieves are an important class of microporous materials and are useful for industrial catalysis and separations. They have been synthesized exclusively by the use of expensive and environmentally unfriendly organic structure‐directing agents. Now the synthesis of SAPO molecular sieves is reported with MER, EDI, GIS, and ANA topologies under wholly inorganic conditions. Multinuclear MAS NMR analyses demonstrate the presence of Si, Al, and P atoms in their frameworks. These SAPO materials all have unusually high framework charge densities (0.25–0.46), owing to the small size of alkali metal cations used as an inorganic structure‐directing agent. A continuous Si increase in the synthesis gel for MER‐type SAPO molecular sieves led to the formation of framework Si(0Al) units, decreasing the number of extra‐framework cations per unit cell and thus making the resulting solid useful for CO2 adsorption.

Characterization and controlling thermal expansion of materials with kosnarite- and langbeinite-type structures

MZr2(TO4)x(PO4)3–x (M=Li, Na, K, Rb, Cs; T=As, V) solid solutions, NaFeZr(PO4)2SO4 and Pb2/3FeZr(PO4)7/3(SO4)2/3 with mineral kosnarite structure and KPbMgTi(PO4)3, K5/3MgE4/3(PO4)3 (E=Ti, Zr) with mineral langbeinite structure have been synthesized. According to the yielded results, which encompass thermal expansion data and crystallographic information about the structure of individual compounds and solid solutions, the meaningful selection of compounds with kosnarite and langbeinite structure for novel materials with controllable thermal expansion was carried out. The potassium-, rubidium-, and cesium-containing arsenates, arsenate–phosphates, vanadate–phosphates and Pb2/3FeZr(PO4)7/3(SO4)2/3 are low expansion materials (αav<2×10−6K−1); sodium–zirconium arsenate and sodium–zirconium and lithium–zirconium arsenate–phosphates, vanadate–phosphates and K5/3MgZr4/3(PO4)3 have intermediate thermal expansion (3×10−6K−1<αav<7×10−6K−1); and lithium–zirconium arsenate, KPbMgTi(PO4)3, K5/3MgTi4/3(PO4)3 are the high expansion material (αav>7×10−6K−1). The present results demonstrate that change of the size of alkali metal cation, anion substitution and varying of solid solution composition can produce kosnarite ceramics with controlled linear thermal expansion coefficients and extremely low thermal expansion anisotropy or langbeinite ceramics with isotropic expansion.

Alkali Metal Variation and Twisting of the FeNNFe Core in Bridging Diiron Dinitrogen Complexes.

Alkali metal cations can interact with Fe–N2 complexes, potentially enhancing back-bonding or influencing the geometry of the iron atom. These influences are relevant to large-scale N2 reduction by iron, such as in the FeMoco of nitrogenase and the alkali-promoted Haber–Bosch process. However, to our knowledge there have been no systematic studies of a large range of alkali metals regarding their influence on transition metal–dinitrogen complexes. In this work, we varied the alkali metal in [alkali cation]2[LFeNNFeL] complexes (L = bulky β-diketiminate ligand) through the size range from Na+ to K+, Rb+, and Cs+. The FeNNFe cores have similar Fe–N and N–N distances and N–N stretching frequencies despite the drastic change in alkali metal cation size. The two diketiminates twist relative to one another, with larger dihedral angles accommodating the larger cations. In order to explain why the twisting has so little influence on the core, we performed density functional theory calculations on a simplified LFeNNFeL model, which show that the two metals surprisingly do not compete for back-bonding to the same π* orbital of N2, even when the ligand planes are parallel. This diiron system can tolerate distortion of the ligand planes through compensating orbital energy changes, and thus, a range of ligand orientations can give very similar energies.

ChemInform Abstract: New Niobium Selenites, ANbO(SeO3)2 (A: Na, K, Rb, and Cs): Effect of Alkali Metal Cation Size on the Dimensionality and Intraoctahedral Distortion.

AbstractSingle crystals of MNbO(SeO3)2 (M: Na, K, Rb, Cs) are grown by solid state reaction of M2CO3 and Nb2O5 in a reactive SeO2 flux (evacuated silica tubes, 400 °C, 3 d; cooling to 25 °C at a rate of 6 °C/h).

The Influence of Alkali Metal Cation Size on the Formation and Dissociation of Crown Ether Fullerene Dimers in Electrospray Mass Spectrometry

Crown ether fullerenes, C60H(cr – H), form two different dimers in electrospray ionization mass spectrometry, a noncovalently bound, metal-bridged dimer [C60H(cr – H)]2M+, and a singly bonded fullerene dimer of the type (cr – H)–C60–C60–(cr – H)Mnn+, with n = 1, 2. In this work, the dependence of both the formation and the dissociation of these dimers on the respective sizes of the crown ether moiety (12cr4, 15cr5, 18cr6) and of the alkali metal ion (M+ = Li+, Na+, K+, Rb+, Cs+) is studied. The size ratio of crown ether cavity to metal cation size has a profound influence on the formation of the noncovalent dimers, [C60H(cr – H)]2M+. These are only formed if the cation is larger than the crown ether cavity. Also, the doubly charged, covalent dimers [C60(cr – H)]2M22+ show a dependence on the size ratio. The proposed formation mechanism involves the recombination of two C60(cr – H)M•+ radical cations, which can only occur if the repulsion between the two charges is sufficiently reduced by encapsulating the...

New niobium selenites, ANbO(SeO3)2 (A = Na, K, Rb, and Cs): Effect of alkali metal cation size on the dimensionality and intraoctahedral distortion

Four new alkali metal niobium selenites with both families of second-order Jahn-Teller distortive (SOJT) cations, ANbO(SeO3)2 (A = Na, K, Rb, and Cs), have been synthesized through standard solid state reactions using A2CO3, Nb2O5, and SeO2 in sealed fused silica tubes. Crystal structures of all four materials have been determined by single crystal X-ray diffraction. While NaNbO(SeO3)2 is configured with corner-shared zigzag chains of NbO6 octahedra and SeO3 intrachain connectors, three isostructural ANbO(SeO3)2 (A = K, Rb, and Cs) are arranged with corrugated layers that are composed of NbO6 octahedra and SeO3 trigonal pyramids. More detailed structural investigations indicate that the size and the coordination environment of alkali metal cations particularly affect the backbone geometries and the dimensions of the reported materials. With ANbO(SeO3)2 (A = K, Rb, and Cs), the alkali metal cations in between the layers also influence the extent of octahedral distortions. Full characterizations including thermal analyses, infrared and UV–vis diffuse reflectance spectroscopy, intraoctahedral distortions, and local dipole moment calculations are also presented.

ChemInform Abstract: Macroscopic Polarity Control with Alkali Metal Cation Size and Coordination Environment in a Series of Tin Iodates.

AbstractSingle crystals of (IIIa—e) and (V) are hydrothermally grown and characterized by single crystal XRD, IR and UV/VIS spectroscopy, SEM, second harmonic generation measurements, and piezoelectric and polarization measurements.

Macroscopic polarity control with alkali metal cation size and coordination environment in a series of tin iodates

The IO3 groups in Na2Sn(IO3)6 are aligned in a parallel manner attributed to the six-coordinate Na+ cation, whereas the IO3 polyhedra in Cs2Sn(IO3)6 rotate with respect to Sn4+ due to the nine-coordinate Cs+ cation.

Cooperative Effects of Cation Size and Variable Coordination Modes of Te4+ on the Frameworks of New Alkali Metal Indium Tellurites, NaIn(TeO3)2, KIn(TeO3)2, RbInTe3O8, and CsInTe3O8

Four new alkali metal indium tellurites, NaIn(TeO3)2, KIn(TeO3)2, RbInTe3O8, and CsInTe3O8, have been prepared through hydrothermal and solid state synthesis reactions using corresponding alkali metal carbonates, In2O3 [or In(NO3)3·xH2O], and TeO2. The structures of the reported materials have been determined by powder and single crystal X-ray diffraction. The mixed indium tellurites reveal a rich structural chemistry with different channel structures. NaIn(TeO3)2 shows 8-membered rings, whereas stoichiometrically similar KIn(TeO3)2 exhibits both 8- and 12-membered rings in the frameworks. Isostructural RbInTe3O8 and CsInTe3O8 reveal three-dimensional frameworks consisting of InO6, TeO3, and TeO4 groups. Close structural examination suggests that the alkali metal cation size and variable coordination modes of Te(4+) cations cooperatively influence the framework geometries of the new mixed metal tellurites. Detailed characterizations including spectroscopic, elemental, and thermal analyses are introduced. Local dipole moments and out-of-center distortions for the constituent polyhedra are also reported.

Alkali metal cation-hexacyclen complexes: effects of alkali metal cation size on the structure and binding energy.

Threshold collision-induced dissociation (CID) of alkali metal cation-hexacyclen (ha18C6) complexes, M(+)(ha18C6), with xenon is studied using guided ion beam tandem mass spectrometry techniques. The alkali metal cations examined here include: Na(+), K(+), Rb(+), and Cs(+). In all cases, M(+) is the only product observed, corresponding to endothermic loss of the intact ha18C6 ligand. The cross-section thresholds are analyzed to extract zero and 298 K M(+)-ha18C6 bond dissociation energies (BDEs) after properly accounting for the effects of multiple M(+)(ha18C6)-Xe collisions, the kinetic and internal energy distributions of the M(+)(ha18C6) and Xe reactants, and the lifetimes for dissociation of the activated M(+)(ha18C6) complexes. Ab initio and density functional theory calculations are used to determine the structures of ha18C6 and the M(+)(ha18C6) complexes, provide molecular constants necessary for the thermodynamic analysis of the energy-resolved CID data, and theoretical estimates for the M(+)-ha18C6 BDEs. Calculations using a polarizable continuum model are also performed to examine solvent effects on the binding. In the absence of solvent, the M(+)-ha18C6 BDEs decrease as the size of the alkali metal cation increases, consistent with the noncovalent nature of the binding in these complexes. However, in the presence of solvent, the ha18C6 ligand exhibits selectivity for K(+) over the other alkali metal cations. The M(+)(ha18C6) structures and BDEs are compared to those previously reported for the analogous M(+)(18-crown-6) and M(+)(cyclen) complexes to examine the effects of the nature of the donor atom (N versus O) and the number donor atoms (six vs four) on the nature and strength of binding.

Intrinsic affinities of alkali metal cations for diaza-18-crown-6: Effects of alkali metal cation size and donor atoms on the binding energies

Threshold collision-induced dissociation of alkali metal cation-diaza-18-crown-6 complexes, M+(da18C6), with xenon is studied using guided ion beam tandem mass spectrometry techniques. The alkali metal cations examined here include: Na+, K+, Rb+, and Cs+. In all cases, M+ is the only product observed, corresponding to endothermic loss of the intact da18C6 ligand. The cross section thresholds are analyzed to extract zero and 298K M+da18C6 bond dissociation energies (BDEs) after properly accounting for the effects of multiple ion-neutral collisions, the kinetic and internal energy distributions of the reactants, and the lifetimes for dissociation. Density functional theory calculations at the B3LYP/def2-TZVPPD and B3LYP/6-31+G* levels of theory are used to determine the structures of da18C6 and the M+(da18C6) complexes and provide molecular constants necessary for the thermodynamic analysis of the experimental data. Theoretical BDEs are determined from single point energy calculations at the B3LYP and MP2(full) levels of theory using the def2-TZVPPD and 6-311+G(2d,2p) basis sets using the B3LYP/def2-TZVPPD and B3LYP/6-31+G* optimized geometries. The agreement between B3LYP/def2-TZVPPD theory and experiment is excellent for all four M+(da18C6) complexes. The M+da18C6 BDEs decrease as the size of the alkali metal cation increases, consistent with the electrostatic nature of the binding in these complexes. The M+(da18C6) structures and BDEs are compared to those previously reported for the analogous complexes of 18-crown-6 and hexaaza-18-crown-6, to examine the effects of the donor atoms (N versus O) on the structure and strength of binding.

Alkali metal cation binding affinities of cytosine in the gas phase: revisited.

Binding of metal cations to the nucleobases can influence base pairing, base stacking and nucleobase tautomerism. Gas-phase condensation of dc discharge generated alkali metal cations and thermally vaporized cytosine (DC/FT) has been found to produce kinetically trapped excited tautomeric conformations of the M(+)(cytosine) complexes, which influences the threshold collision-induced dissociation (TCID) behavior. In order to elucidate the effects of the size of alkali metal cation on the strength of binding to the canonical form of cytosine, the binding affinities of Na(+) and K(+) to cytosine are re-examined here, and studies are extended to include Rb(+) and Cs(+) again using TCID techniques. The M(+)(cytosine) complexes are generated in an electrospray ionization source, which has been shown to produce ground-state tautomeric conformations of M(+)(cytosine). The energy-dependent cross sections are interpreted to yield bond dissociation energies (BDEs) using an analysis that includes consideration of unimolecular decay rates, the kinetic and internal energy distributions of the reactants, and multiple M(+)(cytosine)-Xe collisions. Revised BDEs for the Na(+)(cytosine) and K(+)(cytosine) complexes exceed those previously measured by 31.9 and 25.5 kJ mol(-1), respectively, consistent with the hypothesis proposed by Yang and Rodgers that excited tautomeric conformations are accessed when the complexes are generated by DC/FT ionization. Experimentally measured BDEs are compared to theoretical values calculated at the B3LYP and MP2(full) levels of theory using the 6-311+G(2d,2p)_HW* and def2-TZVPPD basis sets. The B3LYP/def2-TZVPPD level of theory is found to provide the best agreement with the measured BDEs, suggesting that this level of theory can be employed to provide reliable energetics for similar metal-ligand systems.

Infrared multiple photon dissociation action spectroscopy of alkali metal cation–cyclen complexes: Effects of alkali metal cation size on gas-phase conformation

The gas-phase structures of alkali metal cationized complexes of cyclen (1,4,7,10-tetraazacyclododecane) are examined via infrared multiple photon dissociation (IRMPD) action spectroscopy and electronic structure theory calculations. The measured IRMPD action spectra of four M+(cyclen) complexes are compared to IR spectra predicted for the stable low-lying conformers of these complexes calculated at the B3LYP/def2-TZVPPD level of theory to identify the structures accessed in the experiments. The IRMPD yields of the M+(cyclen) complexes investigated increase as the size of the alkali metal cation increases, in accordance with the decrease in the strength of alkali metal cation binding. The IRMPD spectrum of the Na+(cyclen) complex is relatively simple, and the features observed are retained for all of the other alkali metal cation–cyclen complexes. New spectral features begin to appear for K+(cyclen) and become very obvious for the Rb+(cyclen) and Cs+(cyclen) complexes. The IRMPD action spectra for the complexes of cyclen to K+, Rb+, and Cs+ are well reproduced by the calculated spectra predicted for the most stable conformations computed. Overall comparisons suggest that only the ground-state conformations of the M+(cyclen) complexes were accessed in the experiments for the complexes to Na+ and K+, whereas evidence for a very small population of the first excited conformers is observed for the complexes to Rb+ and Cs+.

Alkali metal cation–cyclen complexes: Effects of alkali metal cation size on the structure and binding energy

Threshold collision-induced dissociation of alkali metal cation–cyclen complexes, M+(cyclen), with xenon is studied using guided ion beam tandem mass spectrometry techniques. The alkali metal cations examined here include: Na+, K+, Rb+ and Cs+. In all cases, M+ is the only ionic product observed, corresponding to endothermic loss of the intact cyclen ligand. The cross section thresholds are analyzed to extract zero and 298K M+–cyclen bond dissociation energies (BDEs) after properly accounting for the effects of multiple ion-neutral collisions, the kinetic and internal energy distributions of the reactants, and the lifetimes for dissociation. Density functional theory calculations at the B3LYP/def2-TZVPPD and B3LYP/6-31+G* levels of theory are used to determine the structures of cyclen and the M+(cyclen) complexes. Theoretical BDEs are determined from single point energy calculations at the B3LYP/def2-TZVPPD and MP2(full)/def2-TZVPPD levels of theory using the B3LYP/def2-TZVPPD optimized geometries, and also at the B3LYP/6-311+G(2d,2p) and MP2(full)/6-311+G(2d,2p) levels of theory using the B3LYP/6-31+G*optimized geometries. The agreement between theory and experiment is reasonably good for all levels of theory examined, but is best for the calculations performed at the B3LYP/def2-TZVPPD level of theory. The M+–cyclen BDEs decrease as the size of the alkali metal cation increases, consistent with the electrostatic nature of the binding in these complexes. The M+(cyclen) structures and BDEs are compared to those previously reported for the analogous M+(12-crown-4) complexes to examine the effects of the donor atom (N versus O) on the structures and strength of binding.