Bromo dimethyl sulfoxide osmium(II) complexes. Molecular structure of cis,fac-[OsBr2(dmso-S)3(dmso-O)]

Bromo dimethyl sulfoxide osmium(II) complexes were synthesized: trans-[OsBr₂(dmso-S)₄] (1) was obtained by the reaction of K₂[OsBr₆] with DMSO in the presence of SnBr₂ at 100°C and cis,fac-[OsBr₂(dmso-S)₃(dmso-O)] (2) was prepared by thermal isomerization of 1 in a DMSO solution at 150°C. The coordination mode of DMSO molecules was determined by IR and ¹H and ¹³C NMR spectroscopy. X-ray diffraction analysis showed that compound 2 crystallizes in the monoclinic system, space group P2₁/n; a = 8.4711(5) Å, b = 27.7876(15) Å, c = 8.5569(5) Å, β = 115.7110(10)°; Z = 4. The coordination polyhedron of osmium is a distorted octahedron; the osmium environment is formed by two cis-arranged bromine atoms and three fac-S-coordinated and one O-coordinated DMSO molecules. The interconversion of complexes in solutions was studied by UV/Vis and ¹H and ¹³C NMR spectroscopy. In chloroform and DMSO, complex 2 isomerizes to cis-[OsBr₂(dmso-S)₄] and (in the light) to 1. The complexes trans-[OsX₂(dmso-d₆)₄], where X = Cl, Br, were isolated from DMSO-d ₆ and characterized by the IR spectra.     

High resolution photofragment spectroscopy of the gas phase methyl iodide ion

Photodissociation spectra of the molecular ion CH₃I⁺ were obtained with a three stage quadrupole mass spectrometer. Starting from the \(\tilde X^2 E_{3/2} \) ground state, theà ² E _1/2 state was excited with a stilbene 3 cw dye laser. This state predissociates to CH ₊ ³ +I. Measuring the intensity of the CH ₊ ³ fragment ions as a function of the wavelength of the exciting laser, a spectrum showing vibrational and rotational structure was obtained. The vibrational structure was assigned to three progressions ofv ₃ and new vibrational frequencies were determined. From a computer simulation of the (0, 1, 10) band rotational constants were derived. In particular, their dependence on the vibrationv ₃ was studied.     

Penning ionization electron spectrometry of hydrogen chloride

An electron spectrometric study has been performed on HCl using metastable helium and neon atoms as well as neon resonance photons. High resolution electron spectra were obtained with two different beam apparatuses for a mixed He(2¹ S, 2³ S) beam, a pure He(2³ S) beam, and, for the first time, state-selected pure Ne(3s ³ P ₂) and pure Ne(3s ³ P ₀) beams, and for NeI resonance photons. For the system He(2³ S)+HCl the vibrational populationsP(υ′) of the formed HCl⁺ (X ²∏ _i , υ′) and HCl⁺ (A ²Ω⁺, υ′) ions are found to differ from the Franck-Condon factors for unperturbed potentials, indicating slight bond stretching in HCl upon He(2³ S) approach. For He(2¹ S)+HCl the vibrational peak shapes and vibrational populations are substantially different from the He(2³ S) case, pointing to an additional, charge exchanged interaction (He⁺+HCl^?) in the entrance channel of the former system. For the first time, we have detected the electrons in both the He(2¹ S)+HCl and He(2³ S)+HCl spectra associated with the major mechanism for the formation of Cl⁺ ions: energy transfer to repulsive HCl** Rydberg states, dissociating toH(1s) and autoionizing Cl**(¹ D ₂ nl) atoms. For both Ne(³ P ₂)+HCl and Ne(³ P ₀)+HCl, the populationsP(υ′) of both final molecular states HCl⁺ (X, A) agree closely with the Franck-Condon factors at the average relative collision energyē _coll=55 meV and, for HCl⁺ (A ²Ω⁺), also atē _coll=130 meV.     

CARS spectroscopy of the NaH2 collision complex: the nature of the Na(32 P)H2 exciplex — ab initio calculations and experimental results

CARS (Coherent Anti-Stokes Raman Scattering) has been used to analyze the rovibronic state distribution of H₂ after collision with Na(3² P). New lines, which do not correspond to H₂ lines are observed in the CARS spectrum. The experiments point to the formation of a complex of Na(3² P)H₂ inA ² B ₂ symmetry. Ab initio calculations of theA ² B ₂ potential were performed. On this surface the vibrational spectra of the exciplex are evaluated. The observed lines can be attributed to vibrational transitions in the complex, in which combinational modes are involved. The connection of experimental and theoretical results indicates that a collisionally stabilized exciplex molecule is formed during the quenching process.     

Theoretical investigations on nonlinear optical and spectroscopic properties of 6-(3,3,4,4,4-pentafluoro-2-hydroxy-1-butenyl)-2,4-pyrimidinedione: An efficient NLO material

In this study, quantum chemical calculations of geometric parameters, conformational, natural bond orbital (NBO) and nonlinear optical (NLO) properties, vibrational frequencies, ¹H and ¹³C NMR chemical shifts of the title molecule [C₉H₇F₅N₂O₃] in the ground state have been calculated with the help of Density Functional Theory (DFT-B3LYP/6-311++G(d,p)) and Hartree-Fock (HF/6-311++G(d,p)) methods. The optimized geometric parameters, vibrational frequencies, ¹H and ¹³C NMR chemical shifts values are compared with experimental values of the investigated molecules. Comparison between experimental and theoretical results showed that B3LYP/6-311++G(d,p) method is able to provide more satisfactory results. In order to understand this phenomenon in the context of molecular orbital picture, we examined the molecular frontier orbital energies (HOMO, HOMO-1, LUMO, and LUMO + 1), the energy difference (ΔE) between E _HOMO and E _LUMO, electronegativity (χ), hardness (η), softness (S) calculated by HF/6-311++G(d,p) and B3LYP/6-311++G(d,p) levels. The molecular surfaces, Mulliken, NBO, and Atomic polar tensor (APT) charges of the investigated molecule have also been calculated by using the same methods.     

On the determination of HCl+ (A,v′) vibrational populations from HCl+ (A→X) fluorescence spectra: direct comparison between photoionization and penning ionization

Using a beam apparatus, we have measured the HCl⁺ (A,v′→X,v″) fluorescence spectra of HCl⁺ (A,v′) ions formed in HeI (58.4 nm), and NeI (73.6 nm) photoionization and, for the first time, in He (2³ S) Penning ionization under single collision conditions with a wavelength bandwidth around 1 nm. In addition, we have studied Ne (3s ³ P _{2, 0}) Penning ionization of HCl at three different collision energies. The procedure and the problems in extracting HCl⁺ (A,v′) vibrational populations from the data are discussed in some detail. Thedirect comparison of photoionization and Penning ionization data allows definitive conclusions to be drawn on the question whether final state interactions in the Penning reaction change the “nascent” vibrational population (determined by electron spectrometry); for He (2³ S)+HCl, such changes are shown to be absent within the experimental uncertainty (<±10%). For Ne (3s ³ P _{2, 0})+HCl, the HCl⁺ (A,v′=0, 1) populations are also found to be close to those measured by electron spectrometry and essentially independent of collision energy in the range 34–96 meV. From measurements of the fluorescence intensity as a function of HCl density, we have evidence for a fast loss of HCl⁺ (A,v′) ions in collisions with HCl (rate constant around 5·10^?9 cm³s^?1).     

Synthesis and crystal structure of dibenzo-18-crown-6 oxonium perchlorate

An ionized crystalline adduct of dibenzo-18-crown-6, perchloric acid, and water (H₃O)[DB 18K6](ClO₄) is synthesized and structurally studied by X-ray diffraction. The crystals are triclinic: a = 8.582 Å, b = 10.486 Å, c = 26.293 Å, α = 79.45°, β = 82.00°, γ = 79.36°, Z = 4, space group P \(\bar 1\). The structure is solved by a direct method and refined by the full-matrix least-squares method in the anisotropic approximation to R = 0.098 for 5936 independent reflections (CAD4 automated diffractometer, λMoK _α radiation). The structure contains two independent DB18C6 molecules, two independent H₃O⁺ ions, and two independent ClO ₄ ^? ions. The H₃O⁺ ions each lie in the cavity of each of the two DB18C6 molecules and are retained there by three strong hydrogen bonds. Two DB18C6 molecules have close geometric parameters and a butterfly conformation with approximate symmetry C _2v . One of the two independent ClO ₄ ^? anions is disordered over two orientations.     

Synthesis and molecular and crystal structure of the coordination metallopolymer of scandium(III) nitrate with 4,4,10,10-tetramethyl-1,3,7,9,-tetraazospiro[5.5]undecane-2,8-dione

{[Sc₂(C₁₁H₂₀N₄O₂)₃(H₂O)₆]⁶⁺ · 6(NO ₃ ^? )} _n (I), a coordination metallopolymer, has been synthesized for the first time and analyzed by X-ray diffraction. Crystals are tetragonal, space group P $\bar 4$ 2₁ c, a = 21.9797(6) Å, c = 12.7499(6)Å, V = 6159.6(4) ų, ρ_calcd = 1.392 g/cm³, Z = 4. The scandium atom is coordinated to the three oxygen atoms of spirocarbone molecules, which are related to the basal molecules by the symmetry codes 3/2 ? y, 3/2 ? x, 1/2 + z and 3/2 ? y, 3/2 ? x, ? 1/2 + z, and also to three water molecules. The coordination number of scandium is 6. The coordination polyhedron of scandium is a slightly distorted octahedron with OScO angles within 84.70(15)°–95.86(14)° and 172.77(16)°–173.84(15)°. Nitrate anions are in the outer coordination sphere of the metal. The purity of compound I is verified via the Rietveld refinement of its X-ray powder diffraction pattern; the unit cell parameters at room temperature are a = 22.0589(6) Å, c = 12.7806(6) Å, V = 6219.0(6) ų. Lines unrelated to the major phas are not observed in the X-ray diffraction pattern. The content of the major phase is 100 ± 1%.     

Solid solutions of double phosphate hexahydrates in the MgNH4PO4 · 6H2O-Ni2+-H2O system and their dehydration products

Substitutional solid solutions Mg²⁺ ? Ni²⁺ of crystal hydrates Mg_{(1 ? x)}Ni _x NH₄PO₄ · 6H₂O and Mg_{(1 ? x)}Ni _x NH₄PO₄ · H₂O (where 0 < x ≤ 0.65), which have struvite structure and dittmarite structure, respectively, have been studied. Ion exchange Mg²⁺ ? Ni²⁺ influences the condition of M²⁺-H₂O (M²⁺ = Mg²⁺, Ni²⁺) coordination bonds and hydrogen bonds involving coordinated H₂O molecules, as probed by X-ray powder diffraction, thermal analysis, and FTIR spectroscopy. The coordination of water molecules to metal ions in those crystal hydrates is treated to be a factor that determines the propensity of the resulting crystal structures to polymorphism.     

Effect of solvent on complexation between Y3+ cation and 4,13-diaza-18-crown-6 in some binary mixed non-aqueous solvents

The complexation reaction of 4,13-diaza-18-crown-6 (DA18C6) with Y³⁺ cation was studied in some binary mixed solvent solutions of acetonitrile (AN) with methanol (MeOH), ethanol (EtOH), 2-propanol (2-PrOH) and methyl acetate (MeOAc) at different temperatures by conductometric method. The obtained data show that in all studied solutions the stoichiometry of the complex formed between DA18C6 and Y³⁺ cation is 1: 1 [ML], but in the case of pure MeOAc, a 2: 1 [ML₂] complex is formed in solution upon addition of the ligand to the metal salt solution, and further addition of the ligand results in formation of a M₂L₂ complex in solution. This results show that the stoichiometry of the composition of the macrocyclic complexes may be affected by the nature of the solvent system. The results obtained in this study show that the stability constant of the resulting 1: 1 [ML] complex in the binary solvent solutions decreases in the order: AN-MeOAc > AN-2PrOH > AN-MeOH > AN-EtOH. A non-linear relationship was observed between the stability constant (logK _f ) of [Y(DA18C6)]³⁺ complex with the composition of the binary mixed solvent solutions. The corresponding standard thermodynamic parameters (H° _c , Δ S° _c ) for 1: 1 [ML] complexation reaction between DA18C6 and Y³⁺ cation were obtained from temperature dependence of the stability constant of the complex. The results show that, in all solvent systems, the (DAI8C6.Y)³⁺ complex is entropy stabilized, but from enthalpy point of view, depending on the solvent system, it is stabilized or destabilized and the result show that the values of both thermodynamic quantities change with the nature and composition of the binary mixed solvent solutions.     

Time spectroscopy in theA 1∑ u + state of Li2

We have determined effective cross-sections for resonant transfer of excitation energy from state-selected Li₂ molecules to ground state Li atoms $$Li_2 A\left( {\upsilon ',J'} \right) + Li2S \to Li_2 X\left( {\upsilon '',J''} \right) + Li2P$$ with two different experimental techniques. Absolute cross-sections were derived from lifetime measurements of 114 rotational levels of theA-state subject to resonant collisions which belong to vibrational statesv′=4, 5, 6, 7 and 11 of⁶Li₂ and⁷Li₂. Cross-sections amount to several thousand Ų dropping off sharply with a resonance half-width of about 16 cm^?1. The resonance behaviour of the collision cross-section inferred from lifetime data could be confirmed by a double resonance technique probing the number of excited atoms with a second laser while the first laser was scanned over the Li₂ X?A absorption band. Due to their high reliability our data prove a good basis for the test of theoretical models. In contrast to earlier investigations significant deviations were found to exist between the measured cross-sections and those predicted by the first-order dipole-dipole scattering theory.     

A direct hydrogen-1 and phosphorus-31 nuclear magnetic resonance cation solvation study of Al(ClO4)3, Ga(ClO4)3, In(ClO4)3, UO2(ClO4)2, and UO2(NO3)2 in water-acetone-dimethylsulfoxide and water-acetone-hexamethylphosphoramide mixtures

A competitive solvation study of Al(ClO₄)₃, Ga(ClO₄)₃, In(ClO₄)₃, UO₂(ClO₄)₂, and UO₂(NO₃)₂ in water-acetone-dimethylsulfoxide (DMSO) and water-acetone-hexamethylphosphoramide (HMPT) mixtures has been carried out by direct H¹ and P³¹ nuclear magnetic resonance (NMR) techniques. At low temperature, proton and ligand exchange are slow enough in these systems to permit the observation of signals for bulk and coordinated molecules of water and the organic bases (DMSO and HMPT). Both DMSO and HMPT compete effectively with water for coordination sites in the Al³⁺, Ga³⁺, and In³⁺ systems, with steric effects dominating the HMPT results. Both Al³⁺ and In³⁺ are able to bind a maximum of two to three HMPT molecules, for example. In contrast, UO²⁺ is solvated selectively by the organic molecules to the allowed maximum of 4 molecules per cation. H¹ and P³¹ NMR spectral results support the formation of only the mono-, tri-, and tetra-HMPT solvation complexes.     

2-(diphenylphosphinylmethoxy)aniline: Synthesis,vibrational spectra,and crystal structure

The synthesis, vibrational spectra, and X-ray diffraction analysis results for 2-(diphenylphosphinylmethoxy) aniline, 2-[(C₆H₅)₂P(O)OCH₂]C₆H₄NH₂(I), are described. The crystals are monoclinic: a = 18.4515(17) Å, b = 10.5421(12) Å, c = 17.897(2) Å, β = 104.479(8)°, V = 3370.7(6) ų, Z = 8, space group P2₁/c, R = 0.0546 for 1770 reflections with I > 2σ(I). The unit cell contains two crystallographically independent molecules Ia and Ib joined by an N-H …O hydrogen bond between a hydrogen atom of the amino group of aniline in molecule Ia (Ib) and the phosphoryl oxygen atom of molecule Ib (Ia) (O…H 2.18 and 2.19 Å, N…O, 2.979(5) and 3.000(5) Å; NHO angle, 154° and 157°).     

TiO2 and Al2O3 nanoporous oxide layers decorated with silver nanoparticles—active substrates for SERS measurements

Self-organized nanoporous oxide layers (TiO₂, Al₂O₃) exhibiting specific properties, obtained by anodic oxidation at a constant voltage in neutral electrolyte, may serve as attractive SERS substrates for investigating the interactions between an adsorbate and adsorbent, or as a stable platform for detecting various organic compounds. This paper presents the influence of the size of the nanotubes/nanopores and the structure of the porous oxide layers on the SERS enhancement factor, E _F. We used pyridine and mercaptobenzoic acid as probe molecules, since they have a large cross-section for Raman scattering. To characterize the morphology and structure of the oxide layer substrates, before and after vacuum vapor deposition of silver nanoparticles, we applied scanning electron microscopy, X-ray diffraction and surface analytical techniques: AES, XPS and SERS. The results obtained show that for the same amount of Ag (0.02 mg/cm²) the size of the nanopores significantly affects the E _F, which reaches, at a properly chosen nanopore size, distinctly higher values than that characteristic of a standard silver surface roughened by electrochemical cycling, i.e. E _F?>?10⁶. The new Ag/MeO _x –NT composites layer, ensure a good reproducibility of the SERS measurements and exhibit stability over a limited period of time.     

Molecular structure and spectra of titanium and vanadium trifluorides: Complete basis set CCSD(T) study

Quantum chemical study on TiF₃ and VF₃ molecules was carried out using the CCSD(T) coupled cluster method using the triple-, quadruple-, and quintuple-zeta basis set and an extrapolation to the complete basis set limit. The methods of multireference configuration interaction MRCISD+Q and perturbation theory MCQDPT2 were used also. The symmetry of the ground electronic state was determined: ² A′₁ and ³ E″ in TiF₃ and VF₃, respectively. The adiabatic excitation energies were evaluated: AEE(TiF₃, $\tilde A^2 E'' \leftarrow \tilde X^2 A'_1 $ ) = 5000 cm^?1, AEE(VF₃, $\tilde A^3 A'_2 \leftarrow \tilde X^3 E''$ ) = 1000 cm^?1. The Jahn-Teller effect in $\tilde A^2 E''$ state of TiF₃ and $\tilde X^3 E''$ state of VF₃ was investigated. The computed Jahn-Teller stabilization energy D _3h → C _2v amounts to 555 and 292 cm^?1, respectively. The spin-orbit coupling effect on the VF₃ molecular structure and spectrum of electronic states is shown to be quite significant. The calculated vibrational frequencies of TiF₃ are in excellent agreement with IR spectroscopy data. The atomization enthalpies were evaluated: Δ_at H ₂₉₈ ^pO = 430 kcal/mol (TiF₃), 393 kcal/mol (VF₃).     

Spectroscopic characterization,X-ray structure and DFT studies on 4-[3-(2,5-dimethylphenyl)-3-methylcyclobutyl]-N-methylthiazol-2-amine

The titled molecule 4-[3-(2,5-dimethylphenyl)-3-methylcyclobutyl]-N-methylthiazol-2-amine (C₁₇H₂₂N₂S) is synthesized and characterized by ¹H NMR, ¹³C NMR, IR, and X-ray single crystal determination. The compound crystallizes in the monoclinic space group P2_1/c with a = 6.3972(4) Å, b = 9.4988(6) Å, c = 26.016(2) Å and β = 93.496(7)°. In addition to the molecular geometry from the X-ray determination, vibrational frequencies and gauge, including the atomic orbital (GIAO), ¹H and ¹³C NMR chemical shift values of the titled compound in the ground state are calculated using the density functional (B3LYP) method with 6-31G(d), 6-31++G(d,p) and 6-311+G(2d,p) basis sets. The calculated results show that the optimized geometries can well reproduce the crystal structure. Moreover, the theoretical vibrational frequencies and chemical shift values show good agreement with the experimental values. The predicted nonlinear optical properties of the titled compound are greater than those of urea. DFT calculations of the molecular electrostatic potentials and frontier molecular orbitals of the titled compound are carried out at the B3LYP/6-31G(d) level of theory.     

DFT Study of the Molecular Structure,Conformational Preference,HOMO, LUMO,and Vibrational Analysis of 2-, and 3-Furoyl Chloride

Molecular structure, conformational stability and vibrational wave numbers for the rotational isomers of 2-furoyl chloride and 3-furoyl chloride have been computed using the B3LYP method with the 6-311++G(d,p) basis set. From computations, 2-furoyl chloride was predicated to exist predominantly in cis conformation with cis–trans rotational barrier 40.40 kJ·mol^?1, and 3-furoyl chloride was predicated to exist predominantly in the trans conformation with cis–trans rotational barrier 30.17 kJ·mol^?1. The effects of solvents on the conformational stability of all the molecules in nine different solvents (heptane, chloroform, tetrahydrofuran, dichloroethane, acetone, ethanol, methanol, dimethylsulfoxide and water) were investigated. The integral equation formalism of the polarizable continuum model was used for all solution phase computations. The vibrational wave numbers and the corresponding vibrational assignments of the molecules in C₁ symmetry were examined and the simulated infrared spectra of the molecules are reported. The geometrical parameters, highest occupied and lowest unoccupied molecular orbitals, Infrared intensities, and molecular electrostatic potentials results are reported.     

Copper(II) trinuclear complex with trimesic acid salicylidene hydrazone: Synthesis,structure, and magnetic properties

A trinuclear copper(II) complex of trimesic acid salicylidene hydrazone (H₆L) having the composition [Cu₃L · 4Py] · CH₃OH was synthesized and characterized. By X-ray crystallography, the crystals are triclinic: a = 11.7940(4) Å, b = 13.7241(5) Å, c = 15.8993(6) Å, α = 107.4120(10)°, β = 94.2900(10)°, γ = 105.5650(10)°, space group \(P\bar 1\), Z = 2. The number of symmetrically unique reflections having I > 2σ(I) is 7636, R = 0.0465, and R _w = 0.1198. The newly prepared complex contains, in its unit cell, two [Cu₃L · 4Py] molecules which are linked to form a dimer on account of phenoxo bridges (the Cu-O bond length is 2.555 the Cu…Cu distance is 3.348 Separations between them are 9.414, 9.371, and 9.667 of temperature is satisfactorily fitted in terms of a triangular cluster model (?2J = 2.2 cm^?1) with extra intermolecular interactions (zJ′ = 0.4 cm^?1). EPR spectra of solutions at 360–380 K feature a poorly resolved HFS, whose modeling gives a satisfactory result with allowance for the interaction of unpaired electrons with three equivalent copper nuclei (g = 2.098; a _Cu = 25.8 × 10^?4 cm^?1).     

Synthesis and crystal structure of dibenzo-18-crown-6 oxonium perchlorate trihydrate

A hydrated crystalline ionized adduct of dibenzo-18-crown-6 and perchloric acid DB18C6 · H₃O⁺ · CiO ₄ ^? · 3H₂O (I) is synthesized and characterized by X-ray diffraction. The crystals of I are monoclinic: a = 17.760 Å, b = 12.922 Å, β = 124.27°, Z = 4, space group Cc. The structure of I is solved by a direct method and refined by the full-matrix least-squares method in the anisotropic approximation to R = 0.079 for 3294 independent reflections (CAD4 automated diffractometer, λMoK _α radiation). A DB18C6 molecule has a butterfly conformation with the rough symmetry C _2v . An H₃O⁺ · H₂O dimer is situated on one side of the DB18C6 macrocycle, and the ClO ₄ ^? anion and two other water molecules are on the other side. In the crystal of I, the DB18C6 molecules, H₃O⁺ and ClO ₄ ^? ions, and water molecules are linked through intermolecular (interionic) hydrogen bonds to form broad infinite chains running along the z axis.