Sers measurement of oxidation-reduction reactions of adsorbates on gold microstructures

The use of surface enhanced Raman scattering (SERS) to study oxidation-reduction and complexation chemical reactions on Au surfaces is illustrated by: (1) the reaction of Au(CN)₂^? adsorbed on a Au colloid (2140 cm^?) to form Au(CN)₃^2? (2131 cm^?1) on the surface in excess CN^?; (2) the oxidation of Au(CN)₂^? by HNO₃, Cl₂, or Br₂ solutions to form Au(CN)₄^? (2190 cm^?) on a Au colloid; and (3) the dissolution of Au in excess CN^? with O₂. Unlike with Ag surfaces, no SERS is observed when Au powder is exposed to NO, NO₂, SO₂, CO, or CO₂ gases. The surface chemistry of Au is discussed in the light of these reactions.     

EPR study on the chemistry and photochemistry of copper(II) dithiocarbamate mixed-ligand complexes

The thermal and photochemical reactions of the 1∶1 mixed-ligand complexes Cu(dtc)X (X=Cl^?, NO₃ ^?, ClO₄ ^?) have been studied on the ground of their EPR spectra in acetone, CCl₄/i-PrOH (1∶1), and CHCl₃/i-PrOH (1∶1) solutions. The study allows us to get some insight into the behaviour of the mixed-ligand Cu^II(dtc)X complexes with respect to the acceptor properties of halocarbons. In CCl₄/i-PrOH (1∶1) both Cu^II(dtc)⁺…NO₃ ^? and Cu^II(dtc)⁺…ClO₄ ^? undergo thermal reactions within their donor-acceptor complexes with CCl₄ to yield Cu(dtc)Cl. On the time scale of the experiment the reaction does not occur thermally in CHCl₃/i-PrOH (1∶1), but occurs photochemically in both halocarbon/i-PrOH (1∶1) systems in which Cu(dtc)Cl is further photolyzed to CuCl₂. Continuous photolysis of the title compounds in acetone simply bleaches the solution without any intermediate EPR or light absorption.     

Level crossing investigation of the 6p 2 P 3/2 and 7p 2 P 3/2 levels of Cs133, Cs135, and Cs137

The level crossing method has been used for the investigation of the hyperfine structure of the 6p²P_3/2 and 7p²P_3/2 levels of the isotopes Cs¹³³, Cs¹³⁵, and Cs¹³⁷. For the hyperfine coupling constants a and b and for the lifetimes Τ we find: a(6p Cs¹³³)=50.72(3) g_J/?1.345, b(6p Cs¹³³)=?0.38(18) g_J/?1.345 a(7p Cs¹³³)=16.610(6) g_J/?1.3349, b(7p Cs¹³³)=?0.15(3) g_J/?1.3349 a(6p Cs¹³⁵)=53.64(4) g_J/?1.345, b(6p Cs¹³⁵)=7.41(32) g_J/?1.345 a(7p Cs¹³⁵)=17.570(6) g_J/?1.3349, b(7p Cs¹³⁵)=2.35(7) g_J/?1.3349 a(6p Cs¹³⁷)=55.80(4) g_J/?1.345, b(6p Cs¹³⁷)=7.54(20) g_J/?1.345 a(7p Cs¹³⁷)=18.274(6) g_J/?1.3349, b(7p Cs¹³⁷)=2.37(4) g_J/?1.3349 (MHz), Τ(6p²P_3/2)=29.7(2) ?1.345/g_J ns, Τ(7p²P_3/2)=135(1) ?1.3349_Jns. From a comparison with double resonance results the g_J factor of the 7p²P_3/2 level was deduced: g_J(7p²P_3/2=?1.3349(10). Level crossing measurements in the 8p²P_3/2 state of Cs¹³³ give for the g_J factor and the lifetime the following results: g_J(8p²P_3/2)=?1.3353(14), Τ(8p²P_3/2)=310(15) ns. Using recently calculated relativistic correction factors and applying corrections for core polarization and the Sternheimer effect, we obtain for the quadrupole moments: Q(Cs¹³³)=?0.0030 b, Q(Cs¹³⁵)=+0.052 b, Q(Cs¹³⁷)=+0.052 b.     

Characterization of uranium(VI) sorption by organobentonite

The U(VI) sorption on the bentonite modified by hexadecyltrimethylammonium bromide (HDTMA) was studied in the concentration range: 0.0001-0.001 mol/dm³ in the aqueous phase and in the pH range: 3-10. The experiments concerning the pH influence on the molar absorption coefficient c_b of U(VI) in the bentonite phase showed that the species: UO₂²⁺, UO₂(OH)⁺, UO₂(OH)₂ UO₂(OH)₃⁻, UO₂(OH)₄²⁻, (UO₂)₃(OH)₅⁺, (UO₂)₃(OH)₇⁻, present in the aqueous phase, are responsible for uranium sorption. Their sorption parameters K were determined and it is evident that for higher concentrations of HDTMA⁺ cations in the bentonite phase, i.e. for b96-b157 bentonite, the presence of anionic species: UO₂(OH)₃⁻, UO₂(OH)₄²⁻, and (UO₂)₃(OH)₇⁻ in the aqueous phase results in the increase of U(VI) molar absorption coefficient c_b in the sorbent phase.     

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.     

Analysis of the ESR Spectrum of a Rhodium (II) Complex

Abstract

Rh(II) complexes are rather scarce¹ and often form dimeric structures, which are diamagnetic. The ESR spectra of definite Rh(II) species have so far been claimed for Rh in ZnWO₃ ², [Rh S₄C₄(CN)₄]^{2 ?}, ^3′4 [Rh(π-C₅H₅)₂]⁵, [(π-C₅H₅)Rh(π-C₂H₄)₂]⁺⁶, and an irradiation produced [RhCπ₂(CN)₄]^{2 ?} complex.⁷ A detailed analysis has been performed on the first², the second⁴ and the last⁷ complexes. The first system shows an almost axial symmetry and the unpaired electron has been assigned to the d_xy orbital² (the x,y,z axes are defined along the octahedral metal-ligand directions). The sulfur ligand complex and the dichlorotetracyano system have their unpaired electron in the d_Z ² orbital. ^4,7 In the course of studies ^8-10 on oxygenation of a Rh(I) complex, [RhCπ(C₈H₁₄)₂]₂, we observed ¹⁰ that a well defined ESR spectrum develops during the reaction in N,N′-dimethylacetamide (DMA) - lithium chloride media. For experimental detail, reference 10 should be consulted. The data summarized in the table refer to the spectrum B in that reference and are attributed to a Rh(II) species.     

High-resolution analysis of the ν1 and ν5 bands of phosgene 35Cl2CO and 35Cl37ClCO

Fourier transform spectra of phosgene (Cl₂CO) have been recorded in the 11.75 and 5.47 μm spectral regions using a Bruker IFS125HR spectrometer at resolutions of 0.00102 and 0.0015 cm^?1, respectively, leading to the observation of the ν₅ and ν₁ vibrational bands of the two isotopologues ³⁵Cl₂CO and ³⁵Cl³⁷ClCO. The corresponding upper state ro-vibrational levels were fit using Watson-type Hamiltonians and/or a Hamiltonian matrix accounting for resonance effects when necessary. In this way, it was possible to reproduce the upper state ro-vibrational levels to within the experimental accuracy, i.e. ～0.17 × 10^?3 cm^?1. Very accurate rotational and centrifugal distortion constants were derived from the fit together with the following band centres: ν₀(ν_5, ³⁵Cl₂CO) = 851.012737(20) cm^?1, ν₀(ν_5, ³⁵Cl³⁷ClCO) = 849.995451(90) cm^?1, ν₀(ν_{2 +} ν_3, ³⁵Cl³⁷ClCO) = 864.42370(50) cm^?1, ν₀(ν_1, ³⁵Cl₂CO) = 1828.202514(40) cm^?1 and ν₀(ν_1, ³⁵Cl³⁷ClCO) = 1827.246444(20) cm^?1.     

Surface structure of magnetite (111) under hydrated conditions by crystal truncation rod diffraction

X-ray crystal truncation rod (CTR) diffraction under hydrated conditions at circum-neutral pH was used to determine the surface structure of Fe₃O₄(111) following a wet chemical mechanical polishing (CMP) preparation method. The best-fit model to the CTR data shows the presence of two oxygen terminated domains that are chemically inequivalent and symmetrically distinct in the surface contribution ratio of 75% oxygen octahedral-iron (OOI) termination (^aO_2.61–^aO_1.00–^oh1Fe_2.55–^bO_1.00–^bO_3.00–^td1Fe_1.00–^oh2Fe_1.00–^td2Fe_1.00–R) to 25% oxygen mixed-iron (OMI) termination (^bO_1.00–^bO_3.00–^td1Fe₀–^oh2Fe_1.00–^td2Fe_1.00–^aO_3.00–^aO_1.00–^oh1Fe_3.00–R). An adsorbed water layer could not be constrained in the best-fit model. However, bond-valence analyses suggest that both of the surfaces are hydro-oxo terminated. Furthermore, the topmost iron layers of both domains are inferred to be occupied with the redox active Fe²⁺ and Fe³⁺ cations indicating that these irons are the principle irons involved in controlling the surface reactivity of magnetite in industrial and environmentally relevant conditions.     

EPR of Cu2+ in cadmium saccharin [Cd(sac)2(H2O)4]·2H2O and [Cd(sac)2(HydEt-en)2] complexes in single-crystal and powder forms

The electron paramagnetic resonance spectra of Cu²⁺ in [Cd(sac)₂(H₂O₄]·2H₂O and [Cd(sac)₂(HydEt-en)₂] (HydEt-en=N-(2-hydroxyethyl)-ethylenediamine) single crystals and powder were examined at room temperature. A detailed study of the spectra of the compounds indicates the replacement of Cd²⁺ in the host compounds with Cu²⁼. [Cd(sac)₂(H₂O)₄]·2H₂Oshows the presence of two sites for Cu²⁺ and [Cd(sac)₂(HydEt-en)₂] has a single site. The principal values for theg-tensor and the hyperfine tensor for Cu²⁺ in the two compounds were obtained. The Cu²⁺ ion was found to be mostly in the 3d_x ²−y ² orbital and the ground-state wavefunction of [Cd(sac)₂(HydEten]₂] was constructed.     

281—332nm SO+2的光碎片激发谱研究

在超声分子束条件下，利用380.85nm的电离激光使SO₂分子经由［３＋１］共 振增强多光 子电离(REMPI)制备纯净的分子离子SO⁺₂(²A ₁(000))，用另一束解离激光在281 —332nm扫描获得了光解碎片激发(PHOFEX)谱.获得的光碎片SO⁺激发谱基本可以 归属为SO ⁺₂(,)←SO⁺关键词： +₂')" href="#">SO⁺₂ 光解离 光碎片激发谱     

EPR study of the impurity paramagnetic centres in (CaO−Ga2O3−GeO2) glasses

The X-band EPR spectra of Cr³⁺, Mn²⁺, and Fe³⁺ impurity ions in glasses of (CaO?Ga₂O₃?GeO₂) system are investigated in the 77÷300 K temperature range. The experimental data analysis yields the following results: (i) Impurity chromium ions are incorporated into the (CaO?Ga₂O₃?GeO₂) glasses network in Cr³⁺ (3d³,⁴F_3/2) paramagnetic valence state only and occupy the strong distorted oxygen coordinated octahedral sites. (ii) For all activated and non-activated (CaO?Ga₂O₃?GeO₂) glasses the iron impurity is present at concentration roughly 0.01 wt.%. Isotropic EPR signals atg _eff=4.29 andg _eff=2.00 are assigned to Fe³⁺ (3d⁵,⁶S_5/2) ions in the sites with strong rhombic distortion and in the sites with nearly cubic symmetry respectively. (iii) The manganese EPR spectrum in (CaO?Ga₂O₃?GeO₂) glasses is weakly dependent on temperature, doping procedure as well as manganese concentration. EPR spectra of impurity manganese ions in glasses with Ca₃Ga₂Ge₃O₁₂ and Ca₃Ga₂Ge₄O₁₄ compositions are virtually identical and belong to Mn²⁺ (3d⁵,⁶S_5/2) ions. Impurity manganese ions are incorporated into the (CaO?Ga₂O₃?GeO₂) glass network as isolated Mn²⁺ centres and clusters of Mn²⁺ ions.     

Sonochemiluminescence in an aqueous solution of Ru(bpy)3Cl2

The sonochemiluminescence spectra of electron-excited ions ^*[Ru(bpy)₃]²⁺ was registered for the first time during sonolysis of argon saturated aqueous solutions of Ru(bpy)₃Cl₂ with low concentration. At single-bubble sonolysis, the luminescence band of ruthenium is recorded at a concentration of Ru(bpy)₃Cl₂ from 10⁻⁶ M, and at multibubble from 10⁻⁵ M. Possible mechanisms for the appearance of the band of a tris-bipyridyl ruthenium(II) complex on the background of an structureless continuum of water in the spectra of sonoluminescence are analyzed. Based on the results of the comparison of the sonoluminescence spectra of Ru(bpy)₃Cl₂ aqueous solutions with the sonoluminescence spectra of aqueous solutions of rhodamine B (which has a high quantum yield of photoluminescence) it was established that a possible mechanism of sonophotoluminescence does not play a decisive role in ruthenium sonoluminescence. The effect of radical acceptors (O₂, C₂H₅OH, Cd²⁺, I⁻) on ruthenium sonoluminescence is analyzed. The most significant mechanism for the formation of electron-excited ions ^*[Ru(bpy)₃]²⁺ during sonolysis is the sonochemiluminescence in oxidation-reduction reactions involving [Ru(bpy)₃]²⁺ ions and radical products of sonolysis of water (OH, H, e⁻_aq) in the solution volume.     

关於展开子

本文讨论展开子的一些性质。将展开子A_nrst变换至ξ表示,定义为〈ξ|〉=∑ξ₀^-n-1ξ₁^rξ₂^sξ₃^tA_nrst,立即可以看出〈ξ|〉在洛伦兹变换中的变换,正如标准表示中的变换。由此可以立即证明,在标志洛伦兹群的各种不可约表示的两个量J=-1/2I_klI^kl,I=1/2ε^klmnI_klI_mn中,对於展开子而言,I一定等於零。我们也证明了如果我们要求J的本徵函数〈ξ|〉在各处行为正常,便获得J<0,亦即展开子表示为么正的条件。对於在展开子空间(J,0)及其他空间(I′,J′)中作用的矢量算符,我们作出了计算。选择定则为(i)I′=0,J′=1+J±2(1+J)^1/2;(ii)I′=±(1+J)^1/2i,J′=1+J。我们又证明了ξ^vξ_v?/(?ξ^μ)/(ξ^μ)-(1±(1+J)^1/2)ξ_μ将(J,0)空间变为(1+J±2(1+J)^1/2,0)空间。利用上式中取“-”符号的算符,我们可以构成一个像(-ir_μp^μ+k)ψ=0的波动方程,其中ψ只在两个展开子空间中。     

Transformation of Fe(II)-Fe(III) Hydroxysulphite into Hydroxysulphate Green Rusts

Fe(II)-Fe(III) hydroxysulphite Green Rust 1, GR1(SO₃ ^2?), can be obtained by oxidation of Fe(OH)₂ precipitates in aqueous solution and characterised by X-ray diffraction and Mössbauer spectroscopy. In contrast to other Green Rusts (GRs) which then oxidise directly into ferric oxyhydroxides and magnetite, GR1(SO₃ ^2?) first oxidises into a Green Rust two compound, as identified by X-ray diffraction. Mössbauer analysis reveals that this GR2 is the Fe(II)-Fe(III) hydroxysulphate, GR2(SO₄ ^2?). Such an oxidation process, GR1(SO₃ ^2?) → GR2(SO₄ ^2?) confirms that the average oxidation number of Fe increases according to the chemical formulae previously proposed, [Fe^II ₆Fe^III ₂(OH)₁₆]²⁺[SO₃ · mH₂O]^2?, and [Fe^II ₄Fe^III ₂(OH)₁₂]²⁺[SO₄ · nH₂O]^2? for GR1(SO₃ ^2?) and GR2(SO₄ ^2?) with oxidation numbers of 2.25 and 2.33, respectively. The process implies likely the presence of sulphate ions inherent to the oxidation of sulphite in the solution.     

The B 2Σ+–X 2Σ+ Transition of 12C17O+: The 2‐υ″ Progression

Abstract

Three new bands of the B ²Σ⁺–X ²Σ⁺ system of ¹²C¹⁷O⁺ have been investigated using conventional spectroscopic techniques. The spectra were observed in a graphite hollow‐cathode lamp by discharging molecular oxygen (enriched in about 45% of the ¹⁷O₂ isotope) under 1.0 Torr pressure. The rotational analysis of the 2–4, 2–5, and 2–6 bands was performed with the effective Hamiltonian of Brown (Brown et al., J. Mol. Spectrosc. 1979; 74: 294–318). Molecular constants were derived from a merge calculation, including both the current wavenumbers and the spectroscopic data published by the authors previously. The principal equilibrium constants for the ground state of ¹²C¹⁷O⁺ are ω_e=2185.9658(84), ω_e x _e = 14.7674(11), B _e=1.927001(38), α_e=1.8236(22)×10^?2, γ_e=?0.331(28)×10^?4, D _e=6.041(12)×10^?6, β_e=0.100(31)×10^?7 cm^?1, and the equilibrium constants for the excited state are σ_e=45876.499(15), ω_e=1712.201(12), ω_e x _e=27.3528(39), B _e=1.754109(35), α_e=2.8706(57)×10^?2, γ_e = ?1.15(19)×10^?4, D _e=7.491(20)×10^?6, β_e=2.13(12)×10^?7, γ_e = 2.0953(97)×10^?2, and α_γe=?9.46(59)×10^?4 cm^?1, respectively. Rydberg–Klein–Rees potential energy curves were constructed for the B ²Σ⁺ and X ²Σ⁺ states of this molecule, and Franck–Condon factors were calculated for the vibrational bands of the B–X system.     

第Ⅰ类多模叠加态|ψ1(3)〉q中广义磁场的高次和压缩

构造了由多模相干态|{Z_j} > _q、多模真空态|{O_j} >_q和多模相干态的相反态|{-Z_j} > _q三者的线性叠加所组成的第Ⅰ类三态叠加多模叠加态光场|ψ₁⁽³⁾ > _q,利用多模压缩态理论,研究了态|ψ₁⁽³⁾ > _q中广义磁场分量的等幂次高次和压缩效应.结果发现:态|ψ₁⁽³⁾ > _q是一种典型的三态叠加多模非经典光场;当各模的初始相位和 满足一定的取值条件、并且态|ψ₁⁽³⁾〉_q中任意两态的态间初始相位差(θ_pq^(R)-θ_0q⁽⁰⁾)、(θ_nq^(R)-θ_0q⁽⁰⁾)和(θ_pq^(R)-θ_nq^(R))等分别在各自的闭区间内连续变化时,则态|ψ₁⁽³⁾ > _q的广义磁场分量(即第一正交相位分量)总可分别呈现出周期性变化的、等幂次的奇数模-偶数次、偶数模-奇数次、偶数模-偶数次或者奇数模-奇数次的高次和压缩效应.     

Raman and infrared spectra of CdIn2S4 and ZnIn2S4

Four one-phonon Raman lines have been found in CdIn₂S₄ (ZnIn₂S₄) spinels at 92 (72) cm^-1, 186 (184) cm^-1, 246 (253) cm^-1, and 367 (372) cm^-1 for incident photon energies well below the energy gap E_G ～ 2.4 (2.2) eV at 300 K. For photon energies close to E_G, the 367 cm^-1 mode underwent a resonant enhancement in CdIn₂S₄ and four infrared active but Raman forbidden F_1u modes appeared in the CdIn₂S₄ and ZnIn₂S₄ Raman spectra: TO modes at 226 (221) cm^-1 and 309 (312) cm^-1, and LO modes at 274 (272) cm^-1 and 340 (342) cm^-1.     

Optical properties of red, green and blue emitting rare earth benzenetricarboxylate compounds

Red, blue and green emitting rare earth compounds (RE³⁺=Eu³⁺, Gd³⁺ and Tb³⁺) containing the benzenetricarboxylate ligands (BTC) [hemimellitic (EMA), trimellitic (TLA) and trimesic (TMA)] were synthesized and characterized by elemental analysis, complexometric titration, X-ray diffraction patterns, thermogravimetric analysis and infrared spectroscopy. The complexes presented the following formula: [RE(EMA)(H₂O)₂], [RE(TLA)(H₂O)₄] and [RE(TMA)(H₂O)₆], except for Tb-TMA compound, which was obtained only as anhydrous. Phosphorescence data of Gd³⁺-(BTC) complexes showed that the triplet states (T) of the BTC³⁻ anions have energy higher than the main emitting states of the Eu³⁺ (⁵D₀) and Tb³⁺ (⁵D₄), indicating that BTC ligands can act as intramolecular energy donors for these metal ions. The high values of experimental intensity parameters (Ω₂) of Eu³⁺-(BTC) complexes indicate that the europium ion is in a highly polarizable chemical environment. Based on the luminescence spectra, the energy transfer from the T state of BTC ligands to the excited ⁵D₀ and ⁵D₄ levels of the Eu³⁺ and Tb³⁺ ions is discussed. The emission quantum efficiencies (η) of the ⁵D₀ emitting level of the Eu³⁺ ion have been also determined. In the case of the Tb³⁺ ion, the photoluminescence data show the high emission intensity of the characteristic transitions ⁵D₄→⁷F_J (J=0-6), indicating that the BTC ligands are good sensitizers. The RE³⁺-(BTC) complexes act as efficient light conversion molecular devices (LCMDs) and can be used as tricolor luminescent materials.     

Flexibility of paramagnetic (d1) organometallic dithiolene complex [Cp2Mo(dmit)]+• studied by Raman spectroscopy

We report on the experimental and theoretical studies of the flexible organometallic complex Cp₂Mo(dmit) which often exhibits a folding in the solid state. Raman spectra of charge‐transfer salts formed by Cp₂Mo(dmit) with various anions (Br⁻, BF₄⁻, PF₆⁻, SbF₆⁻, ReO(dmit)₂⁻, TCNQF₄⁻) were measured at room temperature using red (632.8 nm) and near‐infrared (780 nm) excitations. The influence of the folding of the MoS₂C₂ metallacycle in [Cp₂Mo(dmit)]^+• cation on the Raman spectra was investigated. Due to folding of [Cp₂Mo(dmit)]^+•, the bands related to the CC and some C S stretching vibrations shift toward lower wavenumbers by about 0.5–0.6 cm⁻¹deg⁻¹. The bond lengths, charge distribution on atoms, highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) energies, and dipole moments for neutral and ionized complex with various folding angles were calculated by density functional theory (DFT) methods. Additionally, the normal vibrational modes and theoretical Raman spectra were calculated and compared with experimental data. Our results indicate that vibrational spectroscopy can be applied for investigation of complex deformations in the solid state. Copyright © 2009 John Wiley & Sons, Ltd.