The electronic structure of the SbF2−5 ion and isoelectronic species

The electronic structure of the SbF²⁻₅ion and the isoelectronic species TeF⁻₅, IF₅ and XeF⁺₅ are calculated using the Discrete Variational X_α-method (DVM-X_α). The nature of chemical Bonding is analysed in terms of a Mulliken population scheme. The factors leading to geometrical distortions of the SbF²⁻₅ coordination polyhedron are discussed. The results of calculations cast doubts on the validity of the assumption that the geometry of the anion is influenced by the lone pair.     

The thermodynamic stability of the LaBr 4 − ion

The thermodynamic stability of the LaBr ₄ ^? anion was for the first time studied by high-temperature mass spectrometry and nonempirical quantum-chemical methods. The experimental and theoretical enthalpies of the reaction $ LaBr_4^ - = Br^ - + LaBr_3 The thermodynamic stability of the LaBr₄⁻ anion was for the first time studied by high-temperature mass spectrometry and nonempirical quantum-chemical methods. The experimental and theoretical enthalpies of the reaction were Δ_r H°(298.15 K) = 302 ± 14 and 303 kJ/mol, respectively. The value Δ_f H° (LaBr₄⁻, g, 298.15 K) = −1105 ± 14 kJ/mol was recommended as the enthalpy of formation of the LaBr₄⁻ anion. Original Russian Text ? M.F. Butman, L.S. Kudin, V.B. Motalov, D.A. Ivanov, V.V. Sliznev, K.W. Kr?mer, 2008, published in Zhurnal Fizicheskoi Khimii, 2008, Vol. 82, No. 5, pp. 885–890.     

A vibrational analysis of the MnO 4 − bands

Teltow'S [14,15] measurements of the permanganate bands are reanalyzed using the level scheme of Ballhausen and Liehr [2]. For KMnO ₄ dissolved in KClO ₄ the components of the first ¹ T ₂ state are found at 18050 cm^–1 18078 cm^–1 and 18043 cm^–1. The breathing frequency of the MnO _– ⁴ unit is in this state 768 ^–1. The electronic origin of the second ¹ T ₂ state is found at 30723 cm^–1 with a breathing frequency of 760 cm^–1.Evidence is further found for a ¹ T ₁ state with its split components located at 14446 cm^–1, 14526 cm^–1 and 14600 cm^–1. The breathing frequency is here found to be 800 cm^–1.Finally for KMnO ₄ dissolved in NaClO ₄ there are indications that one or two spin-triplets are located near 13200 cm^–1.

---

Zusammenfassung TeltowS Messungen des Permanganatspektrums [14, 15] werden mit Hilfe des Termschemas von Ballhausen und Liehr [2] von neuem analysiert. Für KMn ₄ in KClO ₄ findet man die zum ersten ¹ T ₂-Zustand gehörenden Komponenten bei 18050, 18078 und 18043 cm^–1. Die Valenzschwingung des MnO _– ⁴ liegt hier bei 768 cm^–1. Der Ursprung des zweiten ¹ T ₂-Systems wird bei 30723 cm^–1 gefunden, die dazugehörige Valenzfrequenz ist 760 cm^–1.Bei 14446, 14526 und 14600 cm^–1 liegen offenbar die Komponenten eines ¹ T ₁-Terms, wozu eine Valenzfrequenz von 800 cm^–1 gehört.Schließlich findet man für KMnO ₄ in NaClO ₄ Anzeichen für ein oder zwei Spin-Tripletts um 13200 cm^–1.

---

Résumé Les bandes d'absorption du permanganate, mesurées par Teltow [14,15], sont réanalysées à l'aide d'un système de termes proposé par Ballhausen et Liehr [2]. Pour KMnO ₄ dans KClO ₄, on trouve les composants du premier état ¹ T ₁ à 18050, 18078 et 18043 cm^–1. La vibration symétrique du MnO _– ⁴ dans cet état se situe à 768 cm^–1. L'origine électronique du second état ¹ T ₂ est trouvé à 30723 cm^–1, la fréquence oscillatrice correspondante est de 760 cm^–1.Un état ¹ T ₁ avec ses composants à 14446, 14526 et 14600 cm^–1 est mis en évidence, avec une vibration symétrique de 800 cm^–1.Finalement, au cas du KMnO ₄ dissous dans le NaClO ₄, il y a des indications pour un ou deux triplets de spin vers 13200 cm^–1.

     

Structure of the Mo(CN)8 4− ion

Summary The question of the hybridization of the atomic orbitals of Mo in the Mo(CN)₈ ^4– ion is examined, and it is shown that the dodecahedral structure can exist without the participation off electrons.     

Scaled quantum mechanical (SQM) vibrational analysis of AlCl3, Al2Cl6 and the free ion AlCl−4

A series of basis sets are evaluated for AlCl₃ and AlCl⁻₄, and a common scaling factor derived for these compounds was transferred to Al₂Cl₆. 6-31G* calculations, scaled with a common factor of 0.92, give a good fit to all vibrational frequencies for AlCl₃, AlCl⁻₄ and Al₂Cl₆, and there is also a qualitative fit between calculated and observed IR intensities. Extending the basis set does not lead to significant improvements, either for the geometry or for the vibrational frequencies. The calculations verify earlier assignments based on general valence force fields and predict frequencies for some unobserved bands. The SQM force fields for aluminium chlorides show large similarities with the isoelectronic thiophosphates; the main deviations can be attributed to more ionic bonds in the aluminium chlorides. A significant influence on the out-of-plane vibration in AlCl₃ by the basis set on the d-orbitals may indicate that π_dp bonding plays a role. A remarkable and unexpected basis set sensitivity is found for the ν₆(B_1g) ring vibration in Al₂Cl₆.     

Negative ion photoelectron spectroscopy of teo−

We have recorded the photoelectron spectrum of Te0⁻ using a hot-cathode discharge ion source and a negative ion photoelectron spectrometer. The adiabatic electron affinity of TeO is determined to be 1.697±0.022 eV. The negative ion parameters determined in this work are: (w_e″(TeO⁻) = 690 ± 80 cm⁻¹, r_e″(TeO⁻) = 1.884 ± 0.028 Å. and D_o     

Defect structures in the brannerite-type vanadates: VIII. Synthesis of the Mg1−yLiyV2−yMoyO6 and Mg1−x−yØxLiyV2−2x−yMo2x+yO6 solid solutions: Effect of strengthening the crystal lattice by substitution of monovalent ion for bivalent ion

It is shown that MgV₂O₆ and LiVMoO₆, both of the brannerite-type structure, exhibit miscibility in the entire composition range resulting in the formation of MgLi = Mg_1−yLi_yV_2−yMo_yO₆ solid solutions. For y > 0.5 significant capacity of the MgLi matrix to the excess Mo⁶⁺ cations compensated by cation vacancies Ø appears and MgLiØ = Mg_1−x−yØ_xLi_yV_2−2x−yMo_2x+yO₆ solutions become stable. Pronounced negative deviations from Vegard's law are simultaneously observed for MgLi solid solutions. An unusual phenomenon is thus observed: monovalent cation (Li⁺) substituted for bivalent cation (Mg²⁺) strengthens the brannerite-type lattice and increases its toleration to cation vacancies. A similar effect has recently been observed for ZnLi and ZnLiØ solid solutions (K. Mocała and J. Ziółkowski, J. Solid State Chem. 71, 426 (1987)); the effect is absent, however, in the case of MnLi and MnLiØ (J. Ziółkowski, K. Krupa, and K. Mocała, J. Solid State Chem. 48, 376 (1983)). Some speculations concerning this effect and some predictions are offered. X-ray data are listed for MgLi solid solutions of various compositions.     

Thermal analysis of protein–metallic ion systems

Advanced thermal analysis methods, such as temperature modulated DSC (differential scanning calorimetry) and quasi-isothermal TMDSC were used to analyze the protein–metallic ion interactions in silk fibroin proteins. The precise heat capacities were measured and theoretically predicted in this study. To remove bound water and simplify the system, a thermal cycling treatment through both standard DSC and TMDSC was used to detect the underlying heat capacity and reveal the phase transitions of the silk–metallic salts system. Results show that K⁺ metallic salts play the role of plasticizer in silk fibroin proteins, which reduces the glass transition (T_g) of the pure silk protein and negatively affects its structural thermal stability. On the other hand, Ca²⁺ metallic salts act as an anti-plasticizer, and increase the glass transition and the thermal stability of the silk protein structure. This indicates that the thermal analysis methods offer a new pathway to study protein–metallic ion systems, yielding very fruitful information for the study of protein structures in the future.     

Thermodynamic study of the LaNi5−xCux system

The enthalpies of formation of LaNi_5−xCu_x compounds (x = 0, 1, 2, 3, 4, 5) were measured using a calorimetric method and were found to increase linearly from LaNi₅to LaCu₅. A relation taking the substitution of copper for nickel into account is proposed to explain this behaviour. The enthalpies of hydrogenation are calculated from these values for the enthalpies of formation using relations established previously and are compared with experimental data.     

A study of the thermal analysis of the solid solution (AgxK1−xNO3

The effect of partial replacement of K⁺ by Ag⁺ in the mixed system of KNO₃ and AgNO₃ during a set of DSC heating cycles was studied by means of a modern computerized DSC system. Thermal analysis was performed in the vicinity of the phase transition II I for pure KNO₃. The results revealed a large change in enthalpy and the phase transition temperature close to the morphotropic boundary x=0.5–0.6. At this boundary, the transformation enthalpy reached the maximum value of 101 J g^–1. On the basis of the data obtained from this accurate thermal analysis work, a model is suggested for the energy barrier of rotation of the nitrate ion in the mixed nitrate system.     

Tunneling transfer of an electron in oxidation of the HS− ion by an I 3 − complex in aqueous solution

Methods of chemical kinetics have been used in a study of the mechanism of hydrogen sulfide oxidation by iodine. It has been shown that the stage of electron transfer from HS^– to the I ₃ ^/– complex proceeds through a tunneling mechanism. A proposed twinkling model of the reaction mechanism provides an explanation for the observed experimental facts: the dependence of the rate constant on the acidity, viscosity, and ionic strength of the solution; the inverse temperature dependence of the reaction rate constant; the dependence of the reaction rate constant on the concentrations of iodide ion and maleic acid, which are not involved directly in the reaction.B. P. Konstantinov Institute of Nuclear Physics, Russian Academy of Sciences, Gatchina 188350. Translated from Izvestiya Akademii Nauk, Seriya Khimicheskaya, No. 3, pp. 522–536, March, 1992.     

The structure of the SF6 molecule and the SF 6 − anion excited states

The electronic and geometric structures of the ground state and a number of excited states of the SF₆ molecule and the SF ₆ ^– anion have been calculated by the discrete-variation method of the local density-functionals. The anion was found to possess a number of states stable toward the outer electron detachment, and at least one excited state stable toward dissociation. The adiabatic electron affinity (EA) was determined as 3.46 eV at the highest level of theory. This result is correlated to the high EAs of the isovalent compound SeF₆ and TeF₆; however, it does not agree with the presently accepted experimental estimate of 1.0 ± 0.2 eV for the SF₆EA value. The basic anion configuration is octahedral with a S-F bond length of 1.717 Å. The calculated limit for the highest dissociation channel of the ground state SF ₆ ^– SF ₅ ^– + F is 1.5 eV lower than the minimum of the total energy of the neutral molecule; this is in good agreement with experimental estimates.Institute for Chemical Physics, Russian Academy of Sciences, 142432 Chernogolovka. Translated from Izvestiya Akademii Nauk, Seriya Khimicheskaya, No. 3, pp. 641–649, March, 1992.     

Progress in the non-equilibrium vibrational kinetics of hydrogen in magnetic multicusp H− ion sources

The non-equilibrium vibrational kinetics of H₂ in multicusp magnetic discharges has been studied by improving a previous model developed by our groups. In particular, a complete set of V-T (vibrational translation) rates involving H-H₂(v) collisions, calculated by using a three-dimensional dynamics approach, has been inserted into our self-consistent model for better representing the corresponding relaxation. Different experimental situations are simulated with special emphasis on the temporal scales necessary for the different distributions (electron energy and vibrational distributions) to reach stationary values. Finally, a comparison between theoretical and experimental quantities such as vibrational temperature, electron temperature, electron number density and concentration of negative ions (H⁻) shows a satisfactory agreement, thus indicating the basic correctness of our model.     

Evolved gas analysis–ion attachment mass spectrometric analysis of decacarbonyl dimanganese pyrolysis

Evolved gas analysis?Cion attachment mass spectrometric analysis of the principal species produced by the pyrolysis of Mn₂(CO)₁₀ in an infrared image furnace indicated the presence of Mn(CO)₅ in the gas phase. This observation indicates that Mn₂(CO)₁₀ was in equilibrium with Mn(CO)₅. We also studied the temperature dependence of the mass spectrum to obtain information about the kinetics of the Mn₂(CO)₅ dissociation reaction. From the temperature dependence of the peak for Mn(CO)₅Li⁺ (m/z 202), we calculated the apparent activation energy of Mn(CO)₅ dissociation from solid Mn₂(CO)₁₀. The calculated activation energy (274.57?kJ/mol) is compared with previously reported experimental and calculated values of Mn?CMn bond dissociation energies.     

Tetraorganophosphonium and tetraphenylarsonium salts of B5H8− and B6H9−

Eight new quaternary phosphonium or arsonium salts of the polyhedral borane anions B₅H₈⁻ and B₆H₉⁻ have been prepared in order to study the influence of cation size on stability. The salts are, indeed, considerably more stable than those previously prepared, the most stable being the tetraphenylphosphonium and tetraphenylarsonium derivatives. IR and NMR data are reported.     

Spectroscopic influences of ion pairing: Infrared matrix isolation spectra of the M+BF−4 ion pair and its chlorine—fluorine analogs

The matrix isolation technique has been combined with the salt/molecule reaction for the study of contact ion pairs in matrices. The infrared spectrum of the Cs⁺BF⁻₄ ion pair shows a splitting of the triply degenerate BF⁻₄ stretching band due to cesium cation perturbation, with a splitting of nearly 200 cm⁻¹. Normal coordinate calculations support a C_3υ model for the anion, and lead to a value of ΔK of 4.1 for Cs⁺, 4.7 for K⁺ and 3.8 for Tl⁺, where ΔK is the difference in BF stretching force constant between the coordinated fluorine and the non-coordinated fluorines. Similar calculations were carried out for the Cs⁺BCl⁻₄ ion pair, and an optimal value of ΔK = 1.6 was obtained.     

Spectroscopic properties and luminescence concentration quenching of the Pr3+ ion in La1−xPrxOCl

Luminescence spectra ofLa_1−xPr_xOCl(0.01 ≤ x ≤ 0.3) were recorded at liquid helium and room temperature. From these spectra, the energy level diagram of Pr³⁺ in LaOCl was deduced. The decay times of the Pr³⁺ emission in La_1−xPr_xOCl were measured using a high-resolution dye laser system. The linear concentration quenching and exponential decay times are explained assuming cross relaxation and energy transfer between the Pr³⁺ ions.