The anharmonic force fields of PH3, PHF2, PF3, PH5, and H3PO

The cubic and quartic force fields of the title compounds are determined from ab initio SCF calculations using 6-31G^** and TZP/TZ2P basis sets. The computed geometries, vibration-rotation interaction constants, l-doubling constants, anharmonicity constants, and vibrational wavenumbers are compared with the available experimental data, especially for PH₃ and PF₃. Many experimentally unknown spectroscopic constants are predicted. A scaling procedure based on calculated harmonic and anharmonic force fields is proposed for predicting the vibrational wavenumbers of unknown molecules such as PH₅.     

Dipole properties of PH3, PF3, PF5, PCl3, SiCl4, GeCl4, and SnCl4

Experimental and theoretical photoabsorption cross sections combined with constraints provided by the Kuhn–Reiche–Thomas sum rule, the high-energy behaviour of the dipole oscillator strength density, static dipole polarisabilities, and molar refractivity data when available are used to construct dipole oscillator strength distributions for PH₃, PF₃, PF₅, PCl₃, SiCl₄, GeCl₄, and SnCl₄. The distributions are used to predict dipole sum rules S(k), mean excitation energies I(k), and van der Waals C₆ coefficients.     

Electronic excitation in phosphorus-containing molecules. II. Inner shell electron energy loss spectra of PF5, OPF3 AND OPCl3

Electron energy loss Spectroscopy has been used to obtain the inner shell excitation spectra of PF₅, OPF₃ and OPCl₃ in the P 2p,2s (L-shell) region as well as in the respective ligand K shell (F 1s, O 1s) and L shell (Cl 2p and 2s) regions. The spectra are compared and contrasted with earlier reported spectra obtained on the trivalent phosphorus compounds (PH₃, PCl₃, PF₃ and P(CH₃)₃). The spectra were obtained using an impact energy of 2.5keV and a scattering angle of about 1°. The spectra reported here are typical of molecules with electronegative ligands in that the discrete portions of the spectra show strong transitions to virtual molecular orbitais. In addition, intense features are observed at or just beyond the ionization edge attributable to transitions to trapped inner well states, while broad features further into the continuum can be ascribed to σ^*(P—L) shape-resonances (L = ligand). This resonance assignment was supported by a comparison with the corresponding spectra for PF₃ and PCl₃.     

Phase transitions in [NH(CH3)3]2MeCl4 (Me = Cd,Zn,Cu) crystals

Dielectric properties of the new [NH(CH₃)₃]₂ZnCl₄ and [NH(CH₃)₃]₂CdCl₄ crystals from the [(CH₃) _n NH_4-n ]₂MeCl₄ group have been investigated in a wide temperature range (4.2–320 K). A series of phase transitions has been discovered at T₃ = 325 K,T₄ = 251 K,T₅ = 193 K, for [NH(CH₃)₃]₂CdCl₄ and at T₃ = 309 K, T₄ = 282 K, T₅ = 269 K for [NH(CH₃)₃]₂ZnCl₄. A ferroelectric phase has been discovered in the temperature interval T₄—T₅ from the temperature and frequency dependence of the dielectric permittivity ε(T, v). According to optical investigations the existence of ferroelastic phases in the temperature interval T₁ = 349 K–T₂ = 391 K and below T₅ for [NH(CH₃)₃]₂CdCl₄ and both above T₃ and below T₅ for [NH(CH₃)₃]₂ZnCl₄ has been ascertained.     

Syntheses,X‐ray crystal structures,and emission properties of protonated tripyridyltriazines and their ruthenium(II) complexes

A series of metal‐free compounds, ie, planar triprotonated triazine, triazineH₃Cl(PF₆)₂ ( 1 ), planar triprotonated triazineH₃Br(PF₆)₂ ( 2 ), and nonplanar monoprotonated triazineHPF₆ ( 3 ), were prepared. Abbreviations used are triazine = tri‐2‐pyridyltriazine. Ruthenium complexes [RuCl(bpy)(L)](PF₆), [RuCl(bpy)(L)](PF₆)₂, and [Ru(L)₂](PF₆)₂ were also prepared, where bpy is 2,2′‐bipyridine and L's are triazine ( 4 ) and monoprotonated triazine ( 5 ), respectively. Ruthenium complexes [Ru(triazine)₂](PF₆)₂ ( 6 ) were also prepared and crystallized. The X‐ray crystal structures of the 3 compounds 1 , 2 , and 3 and the complex 6 were determined. They were also characterized by electrospray ionization mass spectrometry, UV‐vis spectroscopy, and density functional theory calculations.     

NQR, NMR and Crystal Structure Studies of [C(NH2)3]2HgX4 (X = Br, I)

The crystal structure of [C(NH₂)₃]₂HgBr₄ has been determined at room temperature: monoclinic, space group C2/c, with a = 10.035(2), b = 11.164(2), c = 13.358(3) Å, β = 111.67(3)°, and Z = 4. The crystal consists of planar [C(NH₂)₃]⁺ and distorted tetrahedral [HgBr₄]^2? ions. The Hg atom is located on a two-fold axis such that two sets of inequivalent Br atoms exist in an [HgBr₄]^2? ion. In accordance with the crystal structure, two ⁸¹Br NQR lines widely separated in frequency were observed between 77 and ca. 380 K. [C(NH₂)₃]₂HgI₄ yielded four ¹²⁷I NQR lines ascribable to m = ±1/2 ? ±3/2 transitions, indicating that its crystal structure is different from the bromide complex. The ¹H NMR T ₁ measurements showed a single minimum for the bromide but two minima for the iodide. The analyses based on the C₃ reorientations of the planar [C(NH₂)₃]⁺ ions gave the activation energies of 29.8 kJ mol^?1 for the bromide, and 30.2 and 40.0 kJ mol^?1 for the iodide.     

Intramolecular electron transfer in mixed-valence complexes [(NH3)5Ru-L-Ru(NH3)5]5+ (L = N2, pyz, pym, 4,4’-bipy, bpa)

The dynamics of the intramolecular electron transfer from Ru(II) to Ru(III) in binuclear mixed-valence complexes [NH₃)₅Ru -L-Ru(NH₃)₅]⁵⁺ (L = N₂, pyz, bipy, pym, bpa) is analyzed by the semiempirical CINDO + CI method. Translated from ZhurnalStruktumoi Khimii, Vol. 39, No. 4, pp. 579–590, July–August, 1998.     

Nucleophilicity of metal carbonyl anions in vinylic substitution reactions

Second order rate constants are reported for the reactions of metal carbonyl anions ([M(CO)_nL]^?) with several vinyl halides: PhCCl?C(CN)₂, Z‐ and E‐Ph(CN)C?CHHal (Hal = Cl, Br) which follow the addition–elimination (Ad_NE) substitution mechanism. The obtained data show that the nucleophilic reactivity of [M(CO)_nL]^? anions towards vinyl halides increases in the same order as in aliphatic S_N2 reactions, but much more steeply, by 14 orders of magnitude in the row log{ }: [CpFe(CO)₂]^? (～14), [Re(CO)₅]^? (7.8), [Mn(CO)₅]^? 2.1, [CpW(CO)₃]^? (0.7) > [CpMo(CO)₃]^? (0). A good correlation exists between nucleophilicities of [M(CO)_nL]^? anions towards vinyl (sp²‐carbon) and alkyl halides (sp³‐carbon) with slope 2.7. The reactivity of [M(CO)_nL]^? in a halogen–metal exchange process (with Z‐PhC(CN)?CHI) follows a similar ‘large’ scale as in the Ad_NE process. The nucleophilicity of [M(CO)_nL]^? anions correlates better with their one‐electron oxidation potentials (E_ox) than with their basicity (pK_a of [M(CO)_nL]H). Copyright © 2008 John Wiley & Sons, Ltd.     

Interaction of PH3 coadsorbed with H2, D2, O2 and H2O on Rh(100)

The coadsorption of PH₃ with H₂, D₂, O₂ and H₂O on Rh(100) has been studied using temperature programmed desorption (TPD), Auger electron spectroscopy (AES) and low energy electron diffraction (LEED). The adsorption and molecular desorption of PH₃ is not affected by preadsorbed H₂, D₂ and O₂. Preadsorbed PH₃ blocks H₂ desorption sites while postdosed PH₃ displaces H₂ (D₂₁) from the Rh(100). When D₂ and PH₃ are coadsorbed, no D appears in desorbed phosphine. Preadsorbed O₂ reduces the amount of H₂ desorption (from PH₃ decomposition) and increases the H₂ desorption temperature. There is also some reaction between O(a) and H(a) to form water. Preexposure to H₂O decreases the extent of PH₃ adsorption and of PH₃ decomposition.     

Infrared Spectra of the Square Planar Rhodium(I) Complexes cis-[Rh(CO)2(pyridine) (X)] (X = Cl,Br): Isotopic Labelling Studies and Normal Coordinate Analysis

Abstract

The infrared spectra (4000 - 50 cm^?1) of the square planar rhodium(I) complexes cis-[Rh(CO)₂ (pyridine) (X)] (X = Cl, Br) and their isotopomers with pyridine-d ₅ and ¹³CO have been determined. Assignments are based on earlier studies on pyridine and its complexes and on the shifts in infrared bands which are caused by the isotopic substitutions employed. Normal coordinate analysis following the procedure of Becher and Mattes has been used to confirm the empirical assignments. The two v(RhC) bands are observed near 490 and 450 cm^?1. v(RhN) is found near 210 cm^?1 and v(RhX) occurs at 310 (X = Cl) and 235 (X = Br) cm^?1. At frequencies below 200 cm^?1, the bands are assigned to bending modes in the following sequence: δ (RhN) > δ (CRhC) > δ (RhCl) > γ (RhCl) > γ (RhN).     

Electronic excitations in phosphorus-containing molecules. I. Inner shell electron energy loss spectra of PH3, P(CH3)3, PF3 and PCL3

Electron energy loss Spectroscopy has been used to obtain the inner shell electronic excitation spectra of PH₃, PF₃, PCl₃ and P(CH₃)₃ in the phosphorus L-shell (P 2p, 2s) region as well as the respective ligand K -shells (F 1s, C 1s) and L-shell (Cl 2p and 2s) regions. The spectra were obtained under small momentum transfer conditions so that dipole-allowed transitions dominate. An impact energy of 2.5 ke V was used and inelastically scattered electrons were detected at a typical scattering angle of about 1°. A dipoleforbidden transition of unusual character is observed at 135.11 eV in the P 2p spectrum of PCl₃. Although optically forbidden, as indicated by its absence in a soft X-ray absorption spectrum, the intensity of this transition rises very rapidly with increase in momentum transfer.     

Copper(I) Complexes of N-(2-{[(2E)-2-(4-Nitrobenzylidenyl)Hydrazinyl]Carbonyl}Phenyl)Benzamide and Triphenylphosphine: Synthesis,Characterization and Luminescence Properties

Copper(I) complexes of the formula [Cu(L)(PPh₃)₂]X (1–4) (X = Cl(1), ClO₄(2), BF₄(3) and PF₆(4)) [where L = N-(2-{[(2E)-2-(4-nitrobenzylidenyl)hydrazinyl]carbonyl}phenyl)benzamide; PPh₃ = triphenylphosphine] have been prepared by the condensation of N-[2-(hydrazinocarbonyl)phenyl]benzamide with 4-nitrobenzaldehyde followed by the reaction with CuCl, [Cu(MeCN)₄]ClO₄, [Cu(MeCN)₄]BF₄ and [Cu(MeCN)₄]PF₆ in presence of triphenylphosphine as a coligand. Complexes 1–4 were then characterized by elemental analyses, FTIR, UV-visible and ¹H NMR spectroscopy. Mononuclear copper(I) complexes 1–4 were formed with L in its keto form by involvement of azomethine nitrogen and the carbonyl oxygen along with two PPh₃ groups. A single crystal X-ray diffraction study of the representative complex [(Cu(L)(PPh₃)₂]CIO₄ (2) reveals a distorted tetrahedral geometry around Cu(I). Crystal data of (2): space group = C2/c, a = 42.8596 (9) Å, b = 14.6207 (3) Å, c = 36.4643 (7) Å, V = 20,653.7 (7) ų, Z = 16. Complexes 1–4 exhibit quasireversible redox behaviour corresponding to a Cu(I)/Cu(II) couple. All complexes show blue-green emission as a result of fluorescence from an intra-ligand charge transition (ILCT), ligand to ligand charge transfer transition (LLCT) or mixture of both. Significant increase in size of the counter anion shows marked effect on quantum efficiency and lifetime of the complexes in solution.     

Influence of the outersphere anion on the properties of the spin transition in Fe(4-OCH3-SalEen)2 Y ( Y = PF6, NO3)

The spin transition from a high-spin state to a low-spin state of Fe(III) ions in the compounds Fe(4-OCH₃-SalEen)₂ Y (Y = PF₆, NO₃) is investigated using the electron paramagnetic resonance (EPR) method. It is established that, unlike the compound with the PF₆ anion, the compound with the NO₃ anion is characterized by a temperature hysteresis of the properties of the spin transition. The thermodynamic characteristics of the spin transitions are determined from the EPR data. It is demonstrated that the specific features of the thermal evolution of the formation of the low-spin complexes are consistent with the domain model of the development of the spin transition. Original Russian Text ? T.A. Ivanova, I.V. Ovchinnikov, A.N. Turanov, 2007, published in Fizika Tverdogo Tela, 2007, Vol. 49, No. 11, pp. 2033–2038.     

Theoretical study of cisplatin adsorption on silica

The adsorption of cisplatin and its complexes, cis-[PtCl(NH₃)₂]⁺ and cis-[Pt(NH₃)₂]²⁺, on a SiO₂(1 1 1) hydrated surface has been studied by the Atom Superposition and Electron Delocalization method. The adiabatic energy curves for the adsorption of the drug and its products on the delivery system were considered. The electronic structure and bonding analysis were also performed. The molecule-surface interactions are formed at expenses of the OH surface bonds. The more important interactions are the Cl-H bond for cis-[PtCl₂(NH₃)₂] and cis-[PtCl(NH₃)₂]⁺ adsorptions, and the Pt-O interaction for cis-[Pt(NH₃)₂]²⁺ adsorption. The Cl p orbitals and Pt s, p y d orbitals of the molecule and its complexes, and the s H orbital and, the s and p orbitals of the O atoms of the hydrated surface are the main contribution to the surface bonds.     

81Br NQR Study of [NH3(CH2) n NH3]CdBr4 (n = 4 and 5) and [NH3(CH2) n NH3]ZnBr4 (n = 5 and 6)

⁸¹Br NQR frequencies and differential scanning calorimetry (DSC) were measured as a function of temperature. [NH₃(CH₂)₄ NH₃]CdBr₄ (1) and [NH₃(CH₂)₅NH₃]CdBr₄ (2) showed a doublet and quartet ⁸¹Br NQR spectrum, respectively. [NH₃(CH₂)₅NH₃]ZnBr₄ (3) and [NH₃(CH₂)₆NH₃]ZnBr₄ (4) exhibited a four-line ⁸¹Br NQR spectrum. From the NQR results, it is inferred that (1) and (2) consist of infinite two-dimensional sheets of corner-sharing CdBr₆ octahedra, whereas (3) and (4) have isolated [ZnBr₄]²⁻ tetrahedra. All of the crystals except (1) showed at least one structural phase transition above 380 K.     

Similar luminescent behavior in an established rhenacarborane complex, [3,3-(CO)2-3-NO-closo-3,1,2-ReC2B9H11] and a new complex anion, [3,3,3-(CO)3-8-I-closo-3,1,2-ReC2B9H10]

The compounds [3,3-(CO)₂-3-NO-closo-3,1,2-ReC₂B₉H₁₁] and [NEt₄][3,3,3-(CO)₃-8-I-closo-3,1,2-ReC₂B₉H₁₀] have been shown to be emissive in MeTHF at 77 K, with λ_max in the blue region of the visible spectrum. Emission from [3,3,3-(CO)₃-8-I-closo-3,1,2-ReC₂B₉H₁₀]^-, which has been structurally characterized, is phosphorescent with a single exponential decay lifetime, τ=1.65 ms. The complex [3,3-(CO)₂-3-NO-closo-3,1,2-ReC₂B₉H₁₁] also emits in the solid state at 298 K and has been shown by diffuse-reflectance UV-vis measurement to have a band gap of 2.66 eV.     

Inclusion of relativistic effects into ZDO methods. VI. Stability or Jahn-Teller instability of octahedral gold and copper complexes

Quasirelativstic and relativistic (four-component) versions of the CNDO (Complete Neglect of Differential Overlap) methods have been used in studying the electronic structure of octahedral²[CuF₆]^4–,²[AuF₆]^4– complexes and ^m [Cu₆] ^q , ^m [Au₆] ^q and ^m [Au₆(PH₃)₆] ^q clusters for various charges,q, and spin multiplicities,m. A strong spin-orbit splitting of levels t_1u in [Au₆]²⁺ cluster removes the degeneracy of the ground electronic state³T_1g into a nondegenerate state so that the Jahn-Teller instability disappears as a consequence of the relativistic effect. The phosphine ligands change the redox stability of the cluster as the orbital energies are shifted to higher values. On the contrary, the spin-orbit splitting of completely filled t_2u levels in [AuF₆]^4– is irrelevant since the degeneracy of the ground electronic state²E_g (_8g in the double group notation) remains unchanged. Consequently the Jahn-Teller instability of the octahedral geometry exists and thus a considerable tetragonal distortion appears.Part V: J. Quantum Chem.36 (1989) 727.     

A Study on the Spectra Characterization of Ruthenium(Ii) Complexes

Abstract

A series of Ru(II) complexes have been synthesized, and their electronic spectra and NMR spectroscopy properties were characterized. the chemical shifts of aromatic protons of [Ru(bpy)₃] (PF₆)₂, [Ru(phen)₃](ClO₄)₂ and [Ru(bqdi)₃](PF₆) move downfield, but the resonance peaks of cis-Ru(bpy)₂Cl₂ shift upfield. Within the visible spectra of the ruthenium(II) complexes appear a relatively high oscillator strength which is referred to as the π(Ru)→? (ligands) transition.     

Spin dynamics in (( BEDO-TTF )6[ M (CN)6](H3O,CH3CN)2 ( M = Fe, Cr) crystals

Layered single crystals of the (BEDO-TTF)₆[M(CN)₆](H₃O,CH₃CN)₂ (M = Fe, Cr) compounds with alternating conducting layers of BEDO-TTF and [M(CN)₆](H₃O,CH₃CN)₂ are studied. The contributions to the magnetic susceptibility from charge carriers in BEDO-TTF layers and from the subsystem of localized magnetic moments of iron (or chromium) transition metal complexes are separated for both compounds under investigation. It is revealed that the crystals with [Fe(CN))₆]³⁻ anions at a temperature of ∼80 K and the crystals with [Cr(CN))₆]³⁻ anions at ∼30 K undergo magnetic transitions which are accompanied by drastic changes in the parameters of the EPR lines associated with the BEDO-TTF layers and the subsystem of localized spins of transition metal complexes. It is established that the presence of the BEDO-TTF layers in the structure affects the magnetic properties of iron and chromium hexacyanide complexes. Original Russian Text ? R.B. Morgunov, E.V. Kurganova, T.G. Prokhorova, E.B. Yagubskiĭ, S.V. Simonov, R.P. Shibaeva, 2008, published in Fizika Tverdogo Tela, 2008, Vol. 50, No. 4, pp. 657–663.     

Synthesis of novel 4H-pyrimido[1,6-a]pyrimidines via a one-pot three-component condensation

Abstract  

Highly substituted novel 4H-pyrimido[1,6-a] pyrimidines were prepared by a trifluoromethanesulfonic acid catalyzed one-pot three-component condensation of 4-aminopyrimidines, aldehydes, and β-ketoesters. A preliminary feasibility study was undertaken on these compounds, to assess the potential production of a library of further diversified compounds by nucleophilic replacement of Cl (R¹) or by reaction of electrophiles with the NH₂ (R²) group.