“…Figure shows the four typical Na(eo) conformers that represent each of the four conformational forms: the g‘-tGt conformer is in the cy form in which an anti-intramolecular H-bond is formed; the g−g‘Gt conformer is in the int form in which the intramolecular H-bond between H1 and O2 is in concert with the Na-bond through the O1−H1 hydroxyl group; the t-gGg‘ conformer is in the int ‘ form in which the intramolecular H-bond between H2 and O1 is in competition with the Na-bond for the O1 atom; and the g-tTt conformer is in the st form. Note that in the formation of the Na bond there are some degrees of charge polarization in the Na atom due to the electrostatic multipole moments of the hydroxyl groups and/or the charge transfer from the hydroxyl groups to the Na atom. − In this sense, the intramolecular H-bond and the Na-bond are in concert with each other in the int form and are in competition with each other for the lone pair electrons of the same oxygen atom in the int ‘ form. 1 Schematic diagram of four representative conformers of Na(eo): g‘-tGt, g-g‘Gt, t-gGg‘, and g-tTt.…”
Section: Resultsmentioning
confidence: 99%
“…For the nature of this type of bonding, it has been generally accepted that electrostatic, charge transfer, and dispersive forces may all have some extent of contribution to its stabilization energy. − ,− With the Na(MeOH) and K(MeOH) complexes, the electrostatic interaction energies could be estimated by the dipole−induced dipole interactions. Although the electric polarizability of the potassium atom 43.4 Å 3 is much larger than that of the sodium atom 23.6 Å 3 , this factor is more or less compensated by the comparatively longer K−O bond length of the potassium complex such that the electrostatic interaction energies of the two complexes are actually similar to each other.…”
Section: Resultsmentioning
confidence: 99%
“…In the past few years, molecular complexes formed between the alkali metal atoms and multifunctional Lewis bases, such as K/ethylenediamine, K/1,2-ethanediol (eo), Na/1,2-dimethoxyethane (DME), and Na/12-crown-4, have been studied in this laboratory. − The conformation-dependent bond dissociation energies and photoionization threshold energies of these complexes were specifically emphasized in these works. It appears that the general physical properties of these multidentate complexes, whose geometric structures apparently lie between the simplest form of the complexes and the solvated-like higher cluster systems, could be understood and fitted into the general picture of this class of molecular system. − …”
The molecular complexes of the sodium atoms with methanol and 1,2-ethanediol were generated in a flow reactor and studied with photoionization mass spectrometry. The photoionization efficiency spectra of these complexes were measured and the ionization threshold energies were determined by the method of the Watanabe plots. The conformation-dependent bond dissociation energies and ionization energies of these complexes were also calculated by ab initio molecular orbital methods. The photoionization threshold energies of the sodium/methanol complex was determined to be 4.30 ( 0.02 eV, a value in good agreement with the ab initio prediction. Guided by the theoretical results, the experimental photoionization threshold energy of the cyclic conformers of the sodium/1,2-ethanediol complex was determined to be 3.95 ( 0.02 eV and that of the conformers with the concerted intramolecular H-bond was determined to be 4.32 ( 0.01 eV. The bond dissociation energy of the sodium/methanol complex was determined to be 0.28 eV. The interplay of the sodium complexation bonding and the intramolecular hydrogen bonding and its effects on both the bonding energies and the ionization energies of the conformers were discussed. The conformation-dependent physical properties of the corresponding cationic states of these complexes were also reported. Comparisons of the physical and chemical properties among the sodium/1,2-ethanediol, sodium/1,2-dimethoxyethane, and potassium/1,2-ethanediol complexes were emphasized in this study.
“…Figure shows the four typical Na(eo) conformers that represent each of the four conformational forms: the g‘-tGt conformer is in the cy form in which an anti-intramolecular H-bond is formed; the g−g‘Gt conformer is in the int form in which the intramolecular H-bond between H1 and O2 is in concert with the Na-bond through the O1−H1 hydroxyl group; the t-gGg‘ conformer is in the int ‘ form in which the intramolecular H-bond between H2 and O1 is in competition with the Na-bond for the O1 atom; and the g-tTt conformer is in the st form. Note that in the formation of the Na bond there are some degrees of charge polarization in the Na atom due to the electrostatic multipole moments of the hydroxyl groups and/or the charge transfer from the hydroxyl groups to the Na atom. − In this sense, the intramolecular H-bond and the Na-bond are in concert with each other in the int form and are in competition with each other for the lone pair electrons of the same oxygen atom in the int ‘ form. 1 Schematic diagram of four representative conformers of Na(eo): g‘-tGt, g-g‘Gt, t-gGg‘, and g-tTt.…”
Section: Resultsmentioning
confidence: 99%
“…For the nature of this type of bonding, it has been generally accepted that electrostatic, charge transfer, and dispersive forces may all have some extent of contribution to its stabilization energy. − ,− With the Na(MeOH) and K(MeOH) complexes, the electrostatic interaction energies could be estimated by the dipole−induced dipole interactions. Although the electric polarizability of the potassium atom 43.4 Å 3 is much larger than that of the sodium atom 23.6 Å 3 , this factor is more or less compensated by the comparatively longer K−O bond length of the potassium complex such that the electrostatic interaction energies of the two complexes are actually similar to each other.…”
Section: Resultsmentioning
confidence: 99%
“…In the past few years, molecular complexes formed between the alkali metal atoms and multifunctional Lewis bases, such as K/ethylenediamine, K/1,2-ethanediol (eo), Na/1,2-dimethoxyethane (DME), and Na/12-crown-4, have been studied in this laboratory. − The conformation-dependent bond dissociation energies and photoionization threshold energies of these complexes were specifically emphasized in these works. It appears that the general physical properties of these multidentate complexes, whose geometric structures apparently lie between the simplest form of the complexes and the solvated-like higher cluster systems, could be understood and fitted into the general picture of this class of molecular system. − …”
The molecular complexes of the sodium atoms with methanol and 1,2-ethanediol were generated in a flow reactor and studied with photoionization mass spectrometry. The photoionization efficiency spectra of these complexes were measured and the ionization threshold energies were determined by the method of the Watanabe plots. The conformation-dependent bond dissociation energies and ionization energies of these complexes were also calculated by ab initio molecular orbital methods. The photoionization threshold energies of the sodium/methanol complex was determined to be 4.30 ( 0.02 eV, a value in good agreement with the ab initio prediction. Guided by the theoretical results, the experimental photoionization threshold energy of the cyclic conformers of the sodium/1,2-ethanediol complex was determined to be 3.95 ( 0.02 eV and that of the conformers with the concerted intramolecular H-bond was determined to be 4.32 ( 0.01 eV. The bond dissociation energy of the sodium/methanol complex was determined to be 0.28 eV. The interplay of the sodium complexation bonding and the intramolecular hydrogen bonding and its effects on both the bonding energies and the ionization energies of the conformers were discussed. The conformation-dependent physical properties of the corresponding cationic states of these complexes were also reported. Comparisons of the physical and chemical properties among the sodium/1,2-ethanediol, sodium/1,2-dimethoxyethane, and potassium/1,2-ethanediol complexes were emphasized in this study.
“…However, the identity of these compounds is purely speculative. According to previous studies, three K–N–H compounds are possible candidates: (i) K + NH 3 molecular complexes with a weak interaction between the potassium ion and the ammonia molecule, which could explain the decomposition at U WR = 2 V, (ii) K 2 NH 2 , which has a strong ionic character and is formed between two negatively charged lone pair electrons of a nitrogen atom and the positively charged potassium ions, and (iii) KNH 2 compounds, which can be formed via the reaction:These compounds, whose formation is obviously enhanced by the increased presence of K (or K + ), gradually block the active sites of the catalyst, leading to a decline in the ammonia formation rate, as observed in the electrochemical experiments.…”
The electrochemical
promotion of ammonia synthesis by potassium
ions (K+) on a Co3Mo3N-Ag electrocatalyst
was studied in a K-β″-Al2O3 solid
electrolyte cell. The effect of temperature (400–550 °C), P
H2
/P
N2
feed composition (1.0, 3.0 and 6.0) and applied voltage was
explored in detail. The catalyst was prepared by ammonolysis of the
mixed oxide and was characterized by XRD and SEM. A volcano-type behavior
was found, i.e., around 1% of potassium per total moles of Co3Mo3N improved the ammonia formation rate by as
much as 48%. However, high percentages of potassium act as poison
for the reaction, possibly due to the formation of K–N–H
compounds that block the active sites. Faradaic efficiency (Λ)
values close to 300 are for the first time reported in NH3 synthesis.
“…The conformation-dependent electron populations of Na(12C4) are consistent with the general characteristics of the valence electron in the Na(H 2 O) n and Na(NH 3 ) n clusters. In the mono- to tridentate conformations, both the charge transfer from the ligand to the sodium atom and the shift of the sodium inner valence population to the outer and diffusive valence basis functions suggest that the nature of the Na−O bond still mainly belongs to the category of the localized interactions between the alkali metal atom and simple Lewis base molecules, a subject having been under intensive study for the past two decades or so. − As the conformation reaches the tetradentate C 4 state, the abrupt decrease of both the sodium atomic charge and the inner and outer valence electron populations and the monotonic increase of the diffuse electron population suggest that the valence electron has acquired some character of the valence electron observed in the Li(9C3) 2 complex and the higher Na(NH 3 ) n clusters, i.e., diffusive, Rydberg-type, and solvated-like.…”
The molecular complexes formed between sodium atoms and 12-crown-4 molecules were generated in a flow reactor and studied with photoionization mass spectroscopy. The photoionization threshold energies of these complexes, which are dependent on the complex conformations, were obtained from the analysis of the photoionization efficiency spectra. Ab initio molecular orbital calculations were performed on the possible conformers of these complexes and their corresponding ionic states. With the help of theoretical calculations, the photoionization threshold energy of the C 4 conformer of Na(12-crown-4) was determined to be 3.01 ( 0.02 eV, and the C s conformer to be 3.36 ( 0.04 eV. The photoionization threshold energy of the C i conformer was estimated to be 3.82 ( 0.04 eV. The conformation-dependent valence electron spatial distributions, bond dissociation energies, and photoionization threshold energies of the Na(12-crown-4) complex could be rationalized and classified in the framework of the general properties of the complexes formed between the sodium atoms and Lewis base molecules.
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