Composition and structure of rhenium(VI) complexes as found by EPR and laser mass spectrometry

Reactions of rhenium with oxymonothiophenols in ReO ₄ ^? -HCl (H₂SO₄)-L systems (where L is 3-tert-butyl-2-mercaptophenol or 3-tert-butyl-2-mercapto-6-methylphenol) to form complexes, in which rhenium has an oxidation number of +6, have been studied by means of electron paramagnetic resonance (EPR), spectrophotometry, and surface-assisted laser desorption/ionization methods. The parameters of EPR spectra have been determined, and ion peaks in the mass spectra have been identified. It has been found that the studied complexes are octahedrons distorted in the equatorial plane and the composition of compounds satisfies the Re: L ratio of 1: 3.     

Rydberg states (n = 4–29) of azabicyclo [2.2.2] octane as studied by two-color fluorescence DIP and multiphoton ionization spectroscopies

Two-color fluorescence dip and multiphoton ionization (MPI) spectra have been observed for azabicyclo [2.2.2] octane in a supersonic jet. The spectra showed well-resolved structures consisting of five Rydberg series of n = 4–29. The five Rydberg series were assigned to s, p_z, p_xy, and two d orbitals. From the spectra obtained after exciting the molecule to various vibronic levels in the S₁ (3s) state, the Δν = 0 selection rule was obtained for the Rydberg-Rydberg transition. The same selection rule was found to be preserved also for the transition from the S₁ state to the ion. It was shown that the autoionization of the high Rydberg states to the ion is governed by Δν=?1. The existence of a very fast non-radiative channel was found for the Rydberg state from the ω₂ power dependence on the two-color MPI spectra.     

Improved study of the ionization of hydrogen atoms in thermal energy collisions with metastable He(23 S) atoms

The first electron spectrometric study of the ionizing reaction of metastable He(2³ S ₁) atoms with ground state hydrogen atoms has been carried out with sufficiently high resolution to partially resolve the rotational structure due to formation of rovibrationally excited HeH⁺ (v, J) ions at two different beam source temperatures (300 K and 90 K). The electron energy spectrum has been reproduced in model quantum calculations, using a new large scale ab initio calculation of the He(2³ S)+H(1² S)²Σ-potential. The imaginary part has been adjusted to yield a satisfactory fit to the measured spectrum. The collision energy dependence of the associative ionization electron spectra and of the total and partial ionization cross sections is discussed in some detail. No significant signs for limitations of the used local complex potential method, indicated by results of an earlier study of the He(2³ S)+H(1² S) system, have been found in the present work, in which the calculations were carried out with an improved and corrected program.     

Experimental and theoretical studies of the Bi-excited collision systems He*(23 S) + He*(23 S, 21 S) at thermal and subthermal kinetic energies

We have carried out a comprehensive experimental and theoretical investigation of the autoionizing collision systems He*(2³ S, 2¹ S) + He*(2³ S). We present high resolution electron energy spectra, obtained with a single He* beam (average relative collision energy 〈E _rel〉=1.6 meV) and with crossed He* beams (〈E _rel〉> =61 meV). The spectra show substantial structure, and under single beam conditions fast oscillations due to the interference of incoming and outgoing heavy particle waves in the entrance channels are observed. Accurate ab initio potential curves for the seven lowest He*—He*(Σ) molecular states have been obtained from a Feshbach projection scheme, and width functions for He*(2³ S) + He*(2³ S) have been derived by Stieltjes imaging. Based on these ab initio data, detailed quantum mechanical calculations of the electron spectra have been carried out and provide a thorough understanding of the experimentally observed spectral features. Good overall agreement of the calculated spectra with the experimental data is observed. The close coincidence in the positions of the experimental and theoretical peaks, especially for He*(2³ S) + He*(2³ S), underlines the reliability of the ab initio potentials. In the He*(2¹ S) + He*(2³ S) electron spectrum, the dominant peak is traced to be due to autoionization from the 2³Σ⁺ _g molecular state accessed via an avoided crossing. We also present a detailed discussion of the total ionization cross sections σ_tot and of the fraction σ_AI/σ_tot for associative ionization together with a critical comparison with previous work. The ionization probabilities for close collisions in entrance channels, from which autoionization is spin-allowed, are near unity, and therefore the absolute values and the collision energy dependence of the total cross sections simply reflect the long-range behaviour of the excited state potentials.     

Radical ions : XXVIII. Tris(trimethylsilylmethyl)aminium,N(CH2Si(CH3)3)3: A stable fluxional aminium radical cation

The first ionization potentials of 11 silylmethyl-substituted amines R_3?nN(CH₂Si(CH₃)₃)_n as determined photoelectron spectroscopy range from 9.07 eV to 7.66 eV. The most easily ionized molecule, N(CH₂Si(CH₃)₃)₃, can also be oxidized with AlCl₃ in H₂CCl₂ solution to its aminium radical cation. The ESR spectra recorded between 180 K and 310 K display a strong temperature dependence due to rotations around the >NCH₂bonds.     

Dimethylplatinum (II) complexes with isocyanocoumarin ligands: the crystal structure of cis-dimethylbis-(7-diethylamino-3-isocyanocoumarin)platinum(II)

Platinum complexes that contain isocyanocourmarin ligands have been prepared. [Pt₂Me₄(μ-SMe₂)₂] and [PtPh₂(SMe₂)₂] react with ligands L, (L = 7-diethylamino-3-isocyanocoumarin, Idc; 7-isocyano-4-methylcoumarin, Mic; 7-isocyano-4-trifluoromethylcoumarin, Tic; 3-chloro-4-methyl-7-isocyanocoumarin, Cmic), to give PtR₂L₂, monomers in high yield. The NMR and IR spectra of these complexes are consistent with cis stereochemistry. The UV-Vis absorption spectra of the complexes show bands assigned to ligand-centered transitions. Excitation into the absorption bands of the Idc complexes gives emission at room temperature in methylene chloride solution. The oxidative addition reaction of two of these complexes with methyl iodide has been studied. Platinum (IV) species with fac geometry have been isolated and characterized. Cis-dimethylbis-(7-diethylamino-3-isocyanocoumarin)platinum(II) was characterized by X-ray diffraction.     

Ab initio configuration interaction calculations of the NIs (NO2) core-hole states of p-nitroaniline

The NIs (NO₂) core-hole states of p-nitroaniline are calculated by a Cl procedure that takes account of both orbital relaxation and correlation effects. A satellite peak arising from the excitation 4b₁(Π) → 5b₁(Π) is calculated to occur 26 eV from the main ionization peak, with a relative intensity of 66%. These results are compared with gas-phase photoelectron spectra.     

Synthesis,spectral characterization of the zinc(II) mixed-ligand complexes of N(4)-allyl thiosemicarbazones and N,N,N′,N′-tetramethylethylenediamine,and crystal structure of the novel [ZnL2(tmen)] compound

Mixed-ligand zinc complexes with N,N,N′,N′-tetramethylethylenediamine (tmen) and R-salicylaldehyde N(4)-allyl thiosemicarbazones (R: 3-OCH₃ (L₁), 5-Br(L₂)), [ZnL_1,2(tmen)], were synthesized and the complexes were characterized by elemental analysis, atomic absorption spectrometer, magnetic susceptibility, molar conductivity, electrospray ionization (ESI) and atmospheric pressure chemical ionization (APCI) mass spectra and IR, UV–Vis, ¹H NMR and ¹⁵N spectroscopies. Crystal of [ZnL₂(tmen)] have a slightly distorted square pyramid involving O, N, S atoms of thiosemicarbazone and one N atom of tmen in basal plane and the other N atom of tmen in apex of the pyramid. The non-coordinated allyl group is disordered.     

He(I) and He(II) photoelectron spectra of 1-aza-1,3-butadiene-tricarbonyliron complexes: [Fe(CO)3(R1NCHCHCHR2)]

He(I) and He(II) photoelectron spectra are reported for the 1-aza-1,3-butadienes (R¹NCHCHCHR² denoted by R¹,R²-ABD) t-Bu,Me-ABD and i-Pr,Ph-ABD and their tricarbonyliron complexes [Fe(CO)₃(R¹,R²-ABD)]. Assignments of ionizations from the iron d and ligand orbitals have been made with the aid of He(I)/He(II) intensity ratios and some semi-empirical molecular orbital calculations on the model ligand Me,H-ABD (MNDO) and on the model complex [Fe(CO)₃(H,H-ABD)] (CNDO/S).A remarkable feature is the lowering of the ionization energy from the Fe d_xz/yz² orbital with respect to the other d orbitals (d_xy/d_x²–y²/d_z²)⁶ by about 0.9 eV, an effect which has not been found for the related [Fe(CO)₃(1,3-butadiene)] complexes. The involvement of the nitrogen lone pair in the bonding between the R¹,R²-ABD and Fe(CO)₃ moieties is discussed.     

The conformation and vibrational spectra of 1,5-hexadiene-3-yne (divinylacetylene) and perchloro-1,5-hexadiene-3-yne (perchlorodivinylacetylene)

Infrared spectra of 1,5-hexadiene-S-yne (divinylacetylene) have been recorded in the vapour phase, in solution and in the amorphous and crystalline solid states at 90 K in the region 4000–4020 cm^?1. Correspondingly, IR spectra ofperchloro-1,5-hexadiene-3-yne (perchlorodivinylacetylene) as a melt, as a solute in various solvents and as a solid at 90 K have been obtained. Raman spectra of the two compounds were recorded in the liquid (molten) state including polarization measurements, and as crystalline solids at 90 K.The spectral data indicate that each compound exists as one conformer only in the various states of aggregation. In divinylacetylene the molecular symmetry appears to be anti (C_2h) while for perchlorodivinylacetylene the symmetry is either C_2v (syn) or C₂ (gauche). Vibrational assignments for the spectra of both molecules are presented and the values are compared with the results of normal coordinate analyses.     

Infrared spectra of bis(aniline) and bis (p-toluidine) metal(II) isothiocyanate complexes

The infrared spectra of eight complexes of general formula [ML₂(NCS)₂] (M = Co, Ni, Cu, Zn; L = aniline or p-toluidine) have been determined over the range 4000–4150 cm^?1. Colour, magnetic moments and IR spectra are consistent with polymeric octahedral coordination in the Co(II) and Ni(II) complexes and polymeric tetragonal coordination in the Cu(II) complexes, while the Zn(II) complexes are assigned polymeric octahedral (L = aniline) and tetrahedral (L = p-toluidine) structure on the basis of their IR spectra. Independent ¹⁵N-labelling of the nitrogen atoms of the amino and isothiocyanate groups yields assignments for the internal vibrations of both groups and enables the metal-amine and metal—isothiocyanate stretching vibrations (vM-NH₂ and vM-NCS) to be distinguished. Both vM-NH₂ and vM-NCS are metal ion dependent in the Irving-Williams sequence (Co < Ni < Cu > Zn) expected from their proposed structures while the vN-H and vN-CS vibrations are inversely related to the masses of the coordinated metal ions.     

Photoelectron spectroscopy of f-element organometallic compounds II. Tricyclopentadienyl derivatives of uranium(IV) and thorium(IV)

The photoelectron spectra of some cyclopentadienyI derivatives of uranium(IV) and thorium(IV), namely (C₅H₅)₃ ThCl, (C₅H₅)₃ UCl, (C₅ H₄ CH₃)₃ ThCl, (C₅ H₄ CH₃)₃ UCl, (C₅ H₄ CH₃)₃ UBr and (C₅ H₄ CH₃ )₃ UBH₄, are reported the metal 5f ionization has been detected in all the uranium derivative spectra and a simple molecular orbital scheme qualitatively accounts for the number and position of the observed low energy bands.     

Assignment of the First Photoelectron Band of CH3CHBr(X2A) Using Ab-initio and Density Functional Theory (DFT) Computational Calculations

HeI photoelectron spectra have been recorded for the reaction of atomic fluorine with ethyl bromide at different reaction times. A structured band associated with a short-lived primary reaction product has been recorded at a mixing distance of 12 mm above the photon beam. The adiabatic and vertical ionization energies of this band was measured as 7.78 ± 0.01 and 8.05 ± 0.01 eV, respectively . The average vibrational separation of 700 ± 30 cm⁻¹ was observed in this band. Vertical ionization energies were computed in this work for CH₃CHBr(X²A) and CH₂CH₂Br(X²A) via ΔSCF, ΔMP2 (full) and Δ(B3LYP) levels of theory using different basis sets. Mulliken population analysis and force constant calculations have also been carried out for CH₃CHBr(X²A) and CH₂CH₂Br(X²A) and their singlet cationic states. Comparison between the experimental vertical ionization energies and the corresponding values computed for CH₃CHBr (X²A) and CH₂CH₂Br(X²A) at different levels of theory led to the assignment of the observed first photoelectron band to the ionization of CH₃CHBr(X²A). The observed vibrational structure was assigned to the excitation of C–Br stretching mode in CH₃CHBr⁺ (X¹A).     

The interaction of metastable Ne(3s 3 P 2,3 P 0) atoms with alkali atoms

Using crossed beams of alkali atoms (Li, Na, K) and state-selected metastable Ne(3s ³ P ₂,³ P ₀) atoms, we have measured the energy spectra of electrons resulting in the respective Penning ionization processes at thermal collision energies. The spectra are very different for Ne(³ P ₂) and Ne(³ P ₀): those for Ne(³ P ₂) are broad due to a strongly attractive interaction potential with a well depth of 798 (30) meV (Li), 672(20) meV (Na), and 561(20) meV (K), those for Ne(³ P ₀) are narrow and compatible with van der Waals type attraction (well depth <50 meV). The Ne(³ P ₂) cross section exceeds the one for Ne(³ P ₀) by about an order of magnitude.     

Chemie polyfunktioneller Moleküle. 116. Hydrido-, Deuterido-, Thiolato- und Chlororuthenium(II)-Komplexe des Bis(diphenylphosphino)amins

Chemistry of Polyfunctional Molecules. 116 Hydrido-, Deuterido-, Thiolato-, and Chlororuthenium(II) Complexes of Bis(diphenylphosphino)amine Bis(diphenylphosphino)amine, [(C₆H₅)₂P]₂NH (dppa, 1 ), reacts with [Ru(cod)(cot)] (cod = η-1,5-cyclooctadiene, cot = η-1,3,5-cyclooctatriene) ( 2 ) in a molar ratio of 2 : 1 both in a hydrogen or deuterium atmosphere at room temperature to yield cis-[Ru(H)₂(dppa)₂] ( 3 ) and cis-[Ru(D)₂(dppa)₂] ( 3 a ), respectively. The dihydride complex 3 is very sensitive towards halogenated solvents: dissolution of 3 in CHCl₃ or CH₂Cl₂ produces the monohydride compound trans-[RuCl(H)(dppa)₂] ( 4 ). Treatment of 3 with a threefold excess of tert-butyl mercaptane, Me₃CSH, at room temperature results in the formation of cis-[Ru(H)(SCMe₃)(dppa)₂] ( 5 ). Trans-[RuCl₂(dppa)₂] ( 7 ) can be synthesized by the interaction of [RuCl₂(PPh₃)₃] ( 6 ) with one or two equivalents of 1 in CH₂Cl₂ solution. The NMR spectra of 3, 3 a, 4, 5 and 7 are discussed with respect to molecular stereochemistry and hydrogen-halogen exchange under simultaneous cis-trans rearrangement. In addition to ¹H, ²H, ³¹P{¹H}, and ³¹P NMR, the structures of the different complexes were also derived from 1R, Raman, and mass spectra. The NMR spectra simulation of 3 permits detailed assignments of spin-spin coupling constants. Crystals of cis-[Ru(H)(SCMe₃)(dppa)₂] ( 5 ) are monoclinic, space group P2₁/c, with a = 1 179.9(3), b = 2 228.0(4), c = 1 854.8(6) pm, β = 96.23(2)°, Z = 4, and R_w = 0.062. The structural analysis shows that ruthenium is coordinated by two bidentate organophosphine ligands and by one tert-butyl thiolate molecule. The metal bound hydrogen atom was not located. However, in agreement with ¹H NMR, its position is trans to a phosphorus nucleus.     

Synthesis,structural, spectroscopic,biological and catalytic activity of Co(II), Ni(II) and Cu(II) complexes of benzilic hydrazide (BH)

Co(II), Ni(II) and Cu(II) chloro complexes of benzilic hydrazide (BH) have been synthesized. Also, reaction of the ligand (BH) with several copper(II) salts, including NO₃ ^?, AcO^?, and SO₄ ^? afforded metal complexes of the general formula [CuLX(H₂O) _n ]·nH₂O, where X is the anion and n = 0, 1 or 2. The newly synthesized complexes were characterized by elemental analysis, mass spectra, molar conductance, UV–vis, IR spectra, magnetic moment, and thermal analysis (TG/DTG). The physico-chemical studies support that the ligand acts as monobasic bidentate towards metal ion through the carbonyl and hydroxyl oxygen atoms. The spectral data revealed that the geometrical structure of the complexes is square planar for Cu (II) complexes and tetrahedral for Co(II) and Ni(II) complexes. Structural parameters of the ligand and its complexes have been calculated. The ligand and its metal complexes are screened for their antimicrobial activity. The catalytic activities of the metal chelates have been studied towards the oxidative decolorization of AB25, IC and AB92 dyes using H₂O₂. The catalytic activity is strongly dependent on the type of the metal ion and the anion of Cu(II) complexes.     

Etude structurale par spectrometrie infrarouge et raman des composes de coordination: bis(pyridine)- trichloro aluminium(III) et bis(pyridine)tribromo aluminium(III)

The compounds AlX₃-2Py (X = Cl or Br, Py = C₅H₅N or C₅D₅N) have been prepared by using a method based on an exchange of organic ligands. The infrared and Raman spectra, which have been recorded between 50 and 4000 cm^?1, give strong evidence for the existence of the anion AlCl₄^? (or AlBr₄^?) and show that the cation is AlX₂(Py)⁺₄. The comparison of the spectra with those of the compound NiX₂(Py)₄., and of the cations trans-AlX₂(THF)₄⁺ and cis-AlX₂(bipy)₂⁺ indicates that the cation AlX₂(Py)₄⁺ has the helical configuration (helical trans-octahedron) and allows the assignment of the vibrations.     

The state dependence of the interaction of metastable rare gas atoms Rg*(ms3 P 2,3 P 0) (Rg=Ne,Ar, Kr,Xe) with ground state sodium atoms

Using crossed beams of metastable rare gas atoms Rg*(ms³ P ₂,³ P ₀) (Rg=Ne, Ar, Kr, Xe) and ground state sodium atoms Na(3s ² S _1/2), we have measured the energy spectra of electrons released in the respective Penning ionization processes at thermal collision energies. For Rg*(³ P ₂)+Na(3s), the spectra are quite similar for the different rare gases, both in width and shape; they reflect attractive interactions in the entrance channel with well depthsD* _e [meV] decreasing slowly from Rg=Ne to Xe as follows: 676(18); 602(23); 565(26); 555(30). For Rg*(³ P ₀)+Na(3s), the spectra vary strongly with the rare gas, indicating a change in the character of the interaction from van der Waals type attraction (Ne) to chemical binding for Kr and Xe with well depthsD* _e [meV] of: 51(19); 107(25); 432(30); 530(50). These findings are explained through model calculations of the respective potential curves, in which the exchange and the spin orbit interaction in the excited rare gas and the molecular interaction between the two valences-electrons in terms of suitably chosen singlet and triplet potentials are taken into account. These calculations also explain qualitatively the experimental finding that the ratiosq ₂/q ₀ of the ionization cross sections for Rg*(³ P ₂)+Na and Rg*(³ P ₀)+Na vary strongly with the rare gas from Ne to Xe as follows: 15.8(3.2); 2.6(4); 1.4(2); 1.6(4).     

DFT(B3LYP) calculations of silatranes and their radical cations. First ionization potentials

DFT(B3LYP) and 2 quantum chemical calculations have been performed for 1-substituted silatranes XSi(OCH₂CH₂)N (X = H, CH₃, CH₂Cl, F), their radical cations, and first ionization potentials (IP₁) of these silatranes. The calculated values of IP₁ agree well with the experiment and make it possible to assign the first band to IP₁ in the photoelectron spectra. Analysis of spin density distribution and electronic charges in the radical cations suggests that ionization occurs mainly due to the lone electron pair of nitrogen, participating in intramolecular coordination. The N → Si interaction is broken, and the N...Si distance increases to 335–340 pm.     

Synthesis,characterization, and spectroscopic studies of tetradentate Schiff base chromium(III) complexes

Eight chromium(III) complexes of tetradentate Schiff bases have been prepared in situ by condensing of a substituted salicylaldehyde compound with ethylenediamine. These were characterized by elemental analysis, m.p., IR, molar conductivity, magnetic moment measurements, and electronic spectra. The free ligands were also characterized by ¹H and ¹³C NMR spectra. The ¹³C NMR spectra are discussed in terms of possible substituent effects. The IR and electronic spectra of the free ligand and the complexes are compared and discussed. The electrospray ionization (ESI) mass spectra of four free ligands and their complexes were measured. The deconvolution of the visible spectra of the complexes, C_2v symmetry, in DMSO yields three peaks at ca. 15 600–17 600, 18 400–20 400 and 20 000–23 100, and are assigned to the three d–d transitions, ⁴B_1g → ⁴E_g(⁴T_2g); ⁴B_1g → ⁴B_2g(⁴T_2g); ⁴B_1g → ⁴E_g(⁴T_1g), respectively. The complexes showed magnetic moment in the range of 3.5–4.2 BM which corresponds to three unpaired electrons.