NH4+ Deprotonation at Interfaces Induced Reversible H3O+/NH4+ Co-insertion/Extraction

Ion insertions always involve electrode-electrolyte interface process, desolvation for instance, which determines the electrochemical kinetics. However, it′s still a challenge to achieve fast ion insertion and investigate ion transformation at interface. Herein, the interface deprotonation of NH₄⁺ and the introduced dissociation of H₂O molecules to provide sufficient H₃O⁺ to insert into materials′ structure for fast energy storages are revealed. Lewis acidic ion-NH₄⁺ can, on one hand provide H₃O⁺ itself via deprotonation, and on the other hand hydrolyze with H₂O molecules to produce H₃O⁺. In situ attenuated total reflection-Fourier transform infrared ray method probed the interface accumulation and deprotonation of NH₄⁺, and density functional theory calculations manifested that NH₄⁺ tend to thermodynamically adsorb on the surface of monoclinic VO₂, and deprotonate to provide H₃O⁺. In addition, the inserted NH₄⁺ has a positive effect for stabilizing the VO₂(B) structure. Therefore, high specific capacity (>300 mAh g⁻¹) and fast ionic insertion/extraction (<20 s) can be realized in VO₂(B) anode. This interface derivation proposes a new path for designing proton ion insertion/extraction in mild electrolyte.     

Dynamics of the NH4+ ion in ABX3 perovskites

The Raman and ir spectra of NH₄MnF₃, NH₄ZnF₃ and NH₄MnCl₃ have been measured in order to study the internal vibration modes of NH₄⁺ in different surrounding conditions. The internal force constants have been determined and compared to their values in ammonium halides and in the free ion, Their trends have been discussed in terms of the hydrogen bonding and volume effects. The intraionic polarizability parameters have also been obtained and compared to those of CH₄.     

Influence of Orientational Disorder on the Optical Absorption Properties of the Hybrid Metal-Halide Perovskite CH3NH3PbI3

An experimental and theoretical investigation is reported to analyze the relation between the structural and absorption properties of CH₃NH₃PbI₃ in the tetragonal phase. More than 3000 geometry optimizations were performed to reveal the structural disorder and identify structures with the lowest energies. The electronic structure calculations provide an averaged band gap of 1.674 eV, which is in excellent agreement with the experimental value of about 1.6 eV. The simulations of the absorption spectrum for three representative structures with lowest energy reproduced the absorption shoulders observed in the experimental spectra. These shoulders are assigned to excitations having similar orbital characters and involving transitions between hybridized 6s(Pb)/5p(I) orbitals and 6p(Pb) orbitals. The geometries of the three structures were analyzed and the effects of the inorganic frame and the CH₃NH₃⁺ cations on the absorption properties were estimated. It was found that both changes in the inorganic frame and the CH₃NH₃⁺ cations orientations impact the absorption spectra, by modifying the transitions energies and intensities. This highlights the role of CH₃NH₃⁺ cation in influencing the absorption properties of CH₃NH₃PbI₃ and demonstrates that CH₃NH₃⁺ cation is one of the key elements explaining the broad and nearly constant absorption spectrum in the visible range.     

Infrared spectra of the ammonium ion in crystals: Part IV. Motions of the NH3D+ ion in ammonium perchlorate and in other weakly hydrogen-bonded ammonium compounds

Molecular motion of the ammonium ion has been investigated by IR spectroscopy in a series of ammonium salts which have been reported to be weakly hydrogen-bonded. Infrared spectra of the Isotopically isolated NH₃D⁺ ion in NH₄ClO₄, and NH₄BF₄ have been recorded between 295 and 22 K. Broadening of the N-D stretching bands, in each case, is attributed to short residence time and indicates rapid reorientation of the NH₃D⁺ ion. The band broadening persists down to the lowest temperature. The spectra of the NH₃D⁺ ion in NH₄BPh₄, NH₄SO₃F, NH₄SO₃Me and NH₄PF₆ have been recorded between 295 and 90 K. No significant lifetime broadening has been found in the spectra of the NH₃D⁺ ion in these salts.     

Studies on the exchange characteristics of [Co(NH3)6]3+ in amberlite IRC-50

Summary The exchange of Co(NH₃)₆]³⁺-ions on amberlite IRC-50 resin has been studied at room temperature. For this exchange process the cations are effective in the order: Cs⁺<Rb⁺<K⁺<Na⁺<Li⁺<NH₄ ⁺<Mg²⁺ <Ca²⁺<H⁺ and (C₂H₅)₄N<(CH₃)₄N⁺ ≪Cetyltrimethylammonium-ion <Cetylpyridinium-ion. The logarithm of the selectivity coefficient gives linear graphs when plotted against the radius of the hydrated ions or the reciprocals of theDebye-Hückel parameter?.     

Amminelithium Amidoborane Li(NH3)NH2BH3: A New Coordination Compound with Favorable Dehydrogenation Characteristics

The monoammoniate of lithium amidoborane, Li(NH₃)NH₂BH₃, was synthesized by treatment of LiNH₂BH₃ with ammonia at room temperature. This compound exists in the amorphous state at room temperature, but at ?20 °C crystallizes in the orthorhombic space group Pbca with lattice parameters of a=9.711(4), b=8.7027(5), c=7.1999(1) Å, and V=608.51 ų. The thermal decomposition behavior of this compound under argon and under ammonia was investigated. Through a series of experiments we have demonstrated that Li(NH₃)NH₂BH₃ is able to absorb/desorb ammonia reversibly at room temperature. In the temperature range of 40–70 °C, this compound showed favorable dehydrogenation characteristics. Specifically, under ammonia this material was able to release 3.0 equiv hydrogen (11.18 wt %) rapidly at 60 °C, which represents a significant advantage over LiNH₂BH₃. It has been found that the formation of the coordination bond between ammonia and Li⁺ in LiNH₂BH₃ plays a crucial role in promoting the combination of hydridic B? H bonds and protic N? H bonds, leading to dehydrogenation at low temperature.     

7Li Spin-flip satellites in the EPR sectra of NH3+ -doped LiKSO4

EPR spectra of lithium potassium sulfate doped with NH₃⁺ have been recorded at 9.05 GHz. A pair of satellites can be seen symmetrically situated on either side of the main lines. The separation of the satellite lines from the main line corresponds to the ⁷Li NMR frequency. The distance of the interacting ⁷Li nucleus from the unpaired electron in NH₃⁺ is estimated to be 3.29 Å.     

Ab initio study on the reaction of Y+ + NH3 → Y+ NH + H2

The reaction of Y⁺ + NH₃ → Y⁺ NH + H₂ was theoretically investigated by ab initio MO methods. Two possible pathways (1–1 H₂ loss and 1–2 H₂ loss) on the singlet potential energy surface and reaction mechanism were examined and discussed. The singlet and triplet PESs of this reaction system were compared to confirm the correctness of spin conservation concepts. © 1996 John Wiley & Sons, Inc.     

Free energy calculations involving NH4+ in water

The analysis of the hydration of NH₄⁺ and the estimation of relative or absolute free energies of hydration by means of Monte Carlo computer simulations using different 1-6-12 potential functions is reported. Two electrostatic representations of NH₄⁺ (used respectively by W.L. Jorgensen and P.A. Kollman) in conjunction with two common water models (TIP3P and TIP4P) are considered. A change in relative hydration free energies of 1.7 kcal/mol is found when the NH₄⁺ models are mutated into each other in either TIP3P or TIP4P. The NH₄⁺ → Na⁺ mutation in both solvent models leads to similar but overestimated relative hydration energies of about ?28.7 kcal/mol. Similarly, the NH₄⁺ annihilation significantly overestimates the absolute free energy of hydration.     

Ion–molecule reaction in the gas phase 3—nucleophilic substitution of 17ξ-R-5α,14β-androstane-14,17ξ-diols under [NH4]+ chemical ionization conditions1

Under Ammonia chemical Ionization conditions the source decompositions of [M + NH₄]⁺ ions formed from epimeric tertiary steroid alchols 14 OH_β, 17OH_α or 17 OH_β substituted at position 17 have been studied. They give rise to formation of [M + NH₄? H₂O]⁺ dentoed as [MH_sH]⁺, [M_sH? H₂O]⁺, [M_sH? NH₃]⁺ and [M_sH? NH₃? H₂O]⁺ ions. Stereochemical effects are observed in the ratios [M_sH? H₂O]⁺/[M_sH? NH₃]⁺. These effects are significant among metastable ions. In particular, only the [M_sH]⁺ ions produced from trans-diol isomers lose a water molecule. The favoured loss of water can be accounted for by an S_N2 mechanism in which the insertion of NH₃ gives [M_sH]⁺ with Walden inversion occurring during the ion-molecule reaction between [M + NH₄]⁺ + NH₃. The S_N1 and S_Ni pathways have been rejected.     

About the stability of Au(NH3) 4 3+ in aqueous solution

The transformations of Au(OH) ₄ ^? in aqueous solutions (T = 20°C, I = 1) containing NH₃ and NH ₄ ⁺ (pH 8.1–8.5) were studied. The most pronounced changes in the system occur in the range 0 > log [NH ₄ ⁺ ] > ?2.0 (c _Au = (1?10) × 10^?4 mol/L, the monitoring time was about two weeks). When log [NH ₄ ⁺ ] > 0, Au(NH₃) ₄ ³⁺ dominates together with the amido form Au(NH₃)₃NH ₂ ²⁺ ; when log [NH ₄ ⁺ ] < ?2.0, no changes in the spectra are observed, probably, because of the very low rate of the processes. As c _Au increases in the indicated range, the polymerization rate grows. The equilibrium constant for Au(NH₃)₃OH²⁺ + NH₃ = Au(NH₃) ₄ ³⁺ + OH is log $ K_{4 OH, NH_3 } The transformations of Au(OH)₄⁻ in aqueous solutions (T = 20°C, I = 1) containing NH₃ and NH₄⁺ (pH 8.1–8.5) were studied. The most pronounced changes in the system occur in the range 0 > log [NH₄⁺] > −2.0 (c _Au = (1−10) × 10⁻⁴ mol/L, the monitoring time was about two weeks). When log [NH₄⁺] > 0, Au(NH₃)₄³⁺ dominates together with the amido form Au(NH₃)₃NH₂²⁺; when log [NH₄⁺] < −2.0, no changes in the spectra are observed, probably, because of the very low rate of the processes. As c _Au increases in the indicated range, the polymerization rate grows. The equilibrium constant for Au(NH₃)₃OH²⁺ + NH₃ = Au(NH₃)₄³⁺ + OH is log = −4.2 ± 0.3. This constant was used together with other constants, taking into account possible ligand effects, to estimate the formation constant of Au(NH₃)₄³⁺: logβ₄ = 47 ± 1, E _3/0 = 0.64 ± 0.02 V, log = −8.5 ± 1 (substitution of 4 NH₃ for 4 OH⁻ in Au(OH)₄⁻), log = 17.5 ± 1 (substitution of 4NH₃ for 4Cl⁻ in AuCl₄⁻). Original Russian Text ? I.V. Mironov, 2008, published in Zhurnal Neorganicheskoi Khimii, 2008, Vol. 53, No. 4, pp. 711–715.     

NH4+ Charge Carrier Coordinated H-Bonded Organic Small Molecule for Fast and Superstable Rechargeable Zinc Batteries

Organic small molecules as high-capacity cathodes for Zn-organic batteries have inspired numerous interests, but are trapped by their easy-dissolution in electrolytes. Here we knit ultrastable lock-and-key hydrogen-bonding networks between 2, 7-dinitropyrene-4, 5, 9, 10-tetraone (DNPT) and NH₄⁺ charge carrier. DNPT with octuple-active carbonyl/nitro centers (H-bond acceptor) are redox-exclusively accessible for flexible tetrahedral NH₄⁺ ions (H-bond donator) but exclude larger and rigid Zn²⁺, due to a lower activation energy (0.14 vs. 0.31 eV). NH₄⁺ coordinated H-bonding chemistry conquers the stability barrier of DNPT in electrolyte, and gives fast diffusion kinetics of non-metallic charge carrier. A stable two-step 4e⁻ NH₄⁺ coordination with DNPT cathode harvests a high capacity (320 mAh g⁻¹), a high-rate capability (50 A g⁻¹) and an ultralong life (60,000 cycles). This finding points to a new paradigm for H-bond stabilized organic small molecules to design advanced zinc batteries.     

The methylamine radical cation [CH3NH2]+˙ and its stable isomer the methylenammonium radical cation [CH2NH3]+˙

The potential energy surface for the [CH₅N]^+˙ system has been investigated using ab initio molecular orbital calculations with large, polarization basis sets and incorporating valence-electron correlation. Two [CH₅N]^+˙ isomers can be distinguished: the well known methylamine radical cation, [CH₃NH₂]^+˙, and the less familiar methylenammonium radical cation, [CH₂NH₃]^+˙. The latter is calculated to lie 8 kJ mol^?1 lower in energy. A substantial barrier (176 kJ mol^?1) is predicted for rearrangement of [CH₂NH₃]^+˙ to [CH₃NH₂]^+˙. In addition, a large barrier (202 kJ mol^?1) is found for loss of a hydrogen radical from [CH₂NH₃]^+˙ via direct N—H bond cleavage to give the aminomethyl cation [CH₂NH₂]⁺. These results are consistent with the existence of the methylenammonium ion [CH₂NH₃]^+˙ as a stable observable species. The barrier to loss of a hydrogen radical from [CH₃NH₂]^+˙ is calculated to be 140 kJ mol^?1.     

Isotopic exchange of gaseous ammonia 14NH3 and 15NH3 in sulfonated macroreticular ion exchangers

Adsorption and ¹⁵NH₃ isotopic exchange was performed on dry macroreticular polystyrene ion exchanges crosslinked with varying amounts of divinylbenzene and partially neutralized by ¹⁴NH₃. Data on pressure changes and mass spectrometric analyses of isotopic composition of the gaseous phase were used to calculate equilibrium distribution of ¹⁴NH₃ and ¹⁵NH₃ under various dislocation conditions. It was established that along with the exchange of ¹⁴NH₃ to a gaseous phase, ¹⁵NH₃ penetrates to the mass of ion exchanger. This is evidently due to the migration of ammonia among functional groups. It was found that by thermal desorption under reduced pressure ammonia is released only from functional groups located on the surface of ion exchanger.     

The homogeneous reaction CD4 + NH3 → CD3H + NH2D: The effect of ethane impurities

The homogeneous exchange reaction between tetradeutero methane and ammonia was studied behind reflected shocks in a single-pulse shock tube over the temperature range of 1300–1800°K. The rate of production of CD₃H at the early stages of the reaction in mixtures ranging between 1-4.5% NH₃ and 1–4.3% CD₄ in argon is given by d[CD₃H]/dt=k_b [CD₄]₀[NH₃]₀, where k_b=8 × 10¹⁶ exp (?65.3 × 10³/RT) cm³/mole·sec. This activation energy is considerably lower than the one that may be expected on the basis of a pure free radical mechanism. It is rationalized by C₂D₆ impurities in the methane. No clear answer can be obtained regarding the role of a four-center intermediate in this reaction.     

Quantum chemical study of the reaction of NH4+ with alkylmercury halides in the gas phase

Calculations on the thermochemistry of reactions between NH₄⁺ ions and EtHgX molecules (X = Cl, Br, I) were performed by the MNDO method. The calculations showed the possible existence of two stable isomers of composition [EtHgX, NH₄]⁺ namely [EtHgX…?HNH₃]⁺ and [EtHg(NH₃)XH]⁺. Protonation of EtHgX and of CH₂?CHHgX by NH₄⁺ is characterized by high exothermicity.     

Metallampullen als Mini‐Autoklaven: Synthese und Kristallstrukturen der Ammoniakate [Al(NH3)4Cl2][Al(NH3)2Cl4] und (NH4)2[Al(NH3)4Cl2][Al(NH3)2Cl4]Cl2

Metal Ampoules as Mini‐Autoclaves: Syntheses and Crystal Structures of [Al(NH₃)₄Cl₂][Al(NH₃)₂Cl₄] and (NH₄)₂[Al(NH₃)₄Cl₂][Al(NH₃)₂Cl₄]Cl₂ The salts [Al(NH₃)₄Cl₂]⁺[Al(NH₃)₂Cl₄]^–≡AlCl₃ · 3 NH₃ ( 1 ) and (NH₄⁺)²[Al(NH₃)₄Cl₂]⁺[Al(NH₃)₂Cl₄]^–(Cl^–)₂≡ AlCl₃ · 3 NH₃ · (NH₄)Cl ( 2 ) have been obtained as single crystals during the reactions of aluminum and aluminum trichloride, respectively, with ammonium chloride in sealed Monel metal containers. The crystal structure of 1 was determined again [triclinic, P‐1; a = 574.16(10); b = 655.67(12); c = 954.80(16) pm; α = 86.41(2); β = 87.16(2); γ = 84.89(2)°], that of 2 for the first time [monoclinic, I2/m; a = 657.74(12); b = 1103.01(14); c = 1358.1(3) pm; β = 103.24(2)°].     

A shock tube study of the reaction NH2 + CH4 → NH3 + CH3 and comparison with transition state theory

The rate coefficient for NH₂ + CH₄ → NH₃ + CH₃ (R1) has been measured in a shock tube in the temperature range 1591–2084 K using FM spectroscopy to monitor NH₂ radicals. The measurements are combined with a calculation of the potential energy surface and canonical transition state theory with WKB tunneling to obtain an expression for k₁ = 1.47 × 10³ T ^3.01 e^?5001/T(K) cm³ mol^?1 s^?1 that describes available data in the temperature range 300 –2100 K. © 2003 Wiley Periodicals, Inc. Int J Chem Kinet 35: 304–309, 2003     

Ion cyclotron resonance studies of some reactions of C+ ions

Product distributions and rate constants for the reaction of ground state C⁺ ions with O₂, NO, HCl, CO₂, H₂S, H₂O, HCN, NH₃, CH₄, H₂CO, CH₃OH, and CH₃NH₂ have been measured. Rate constants were obtained using ion cyclotron resonance trapped ion methods at JPL, and product distributions were obtained using a tandem (Dempster-ICR) mass spectrometer at the University of Utah. Rapid carbon isotope exchange has also been observed in C⁺-CO collisions.     

Electronic structure and spectra of [Ru(NH3)5pyz]2+ and [(NH3)5Ru-pyz-Ru(NH3)5]4+

The electronic structure and spectra of [Ru(NH₃)₅pyz]²⁺ and [(NH₃)₅Ru-pyz-Ru(NH₃)₅]⁴⁺ are calculated by the INDO (CINDO-E/S) method. Changes in molecular orbitals, charge distributions, and bond order indices of the pyrazine molecule and [Ru(NH₃)₅pyz]²⁺ complex in the [(NH₃)₅Ru-pyz-Ru(NH₃)₅]⁴⁺ binuclear complex are analyzed. St. Petersburg State University. Translated fromZhurnal Strukturnoi Khimii, Vol. 35, No. 4, pp. 12–23, July–August, 1994. Translated by. O. Kharlamova