Characterization of Ir(ppy)3 and [Ir(ppy)2 bpy]+ by infrared,Raman spectra and surface‐enhanced Raman scattering

The Raman and infrared spectra of fac ‐tris(2‐phenylpyridinato‐N,C2′)iridium(III), Ir(ppy)₃ and surface‐enhanced resonance Raman spectra of bis(2‐phenyl pyridinato‐) (2,2′bipyridine) iridium (III), [Ir(ppy)₂ (bpy)]⁺ cation were recorded in the wavenumber range 150–1700 cm⁻¹, and complete vibrational analyses of Ir(ppy)₃ and [Ir(ppy)₂ (bpy)]⁺ were performed. Most of the vibrational wavenumbers were calculated with density‐functional theory agree with experimental data. On the basis of the results of calculation and comparison of the spectra of both complexes and their analogue [Ru(bpy)₃]²⁺, we assign the vibrational wavenumbers for metal–ligand modes; metal–ligand stretching wavenumbers are 277/307 and 261/236 cm⁻¹ for Ir(ppy)₃, and 311/324, 257/270, 199/245 cm⁻¹ for [Ir(ppy)₂ bpy]⁺. Surface‐enhanced Raman scattering spectra of [Ir(ppy)₂ bpy]²⁺ were measured at two wavelengths on the red and blue edges of the low‐energy metal‐to‐ligand charge‐transfer band. According to the enhanced Raman intensities for the vibrational modes of both ligands ppy and bpy, the unresolved charge‐transfer band is deduced to consist of charge‐transfer transitions from the triplet metal to both ligands ppy and bpy. Copyright © 2010 John Wiley & Sons, Ltd.     

Geometric and algebraic descriptions of the 193Ir nucleus

The structure of ¹⁹³Ir was investigated using the ¹⁹¹Ir(2n_th,γ)_and ¹⁹²Os (d,nγ) reactions. High resolution γ and internal conversion spectrometers as well as different Compton-suppressed spectrometers were used. The collective structures are interpreted within the framework of the asymmetric rotor model. The results are also compared to IBFA-1 and IBFA-2 calculations.     

The Effect of Hg(II) on the Optical Characteristics of Cycloiridated 2-Phenylbenzothiazole Complexes with Chelating Ligands Containing Sulfur Donor Atoms

The [Ir(bt)₂(S^S)], [Ir(bt)₂(S^N)], and [Ir(bt)₂(CH₃CN)₂]PF₆ complexes, where (bt)^? is a deprotonated form of 2-phenylbenzothiazole and (S^S)^? and (S^N)^? are diethyldithiocarbamate, O-ethyldithiocarbonate, 2-mercaptobenzothiazolate, 2-mercaptobenzoxazolate, and 2-mercaptopyridinate ions, and the effect of Hg(II), Cu(II), Cd(II), and Zn(II) cations on the optical characteristics of these complexes are studied by electron absorption spectroscopy and emission spectroscopy. A hypsochromic shift of the absorption and phosphorescence bands of complexes in substituting the (S^S)^? and (S^N)^? chelating ligands with acetonitrile ligands is attributed to a lower energy of d_Ir orbitals compared with the mixed d_Ir/p(S) orbitals. It is shown that the presence of Hg(II) cations results in a hypsochromic shift of the absorption and phosphorescence bands of complexes [Ir(bt)₂(S^S)] and [Ir(bt)₂(S^N)] because of an effective reaction of substitution of chelating ligands to acetonitrile ligands.     

Far-infrared reflection spectra,TO- and LO-phonon frequencies,coupled and decoupled plasmon-phonon modes,dielectric constants,and effective dynamical charges of manganese,iron, and platinum group pyrite type compounds

The far-infrared reflection spectra of hot-pressed samples of the pyrites MX₂ with M = Mn, Fe, Ru, and Os and X = S, Se, and Te and PtY₂ with Y = P, As, and Sb are presented in the range from 40 to 700 cm^?1. The spectra show five reststrahlen bands and more or less free carrier contributions due to deviation from stoichiometry. The oscillator parameters ω_j, ρ_j, γ_j, ω_p, and γ_o, the transverse optical phonon frequencies ω_TO, and the coupled plasmon-phonon frequencies Ω₊ and Ω_? were calculated. The uncoupled longitudinal optical phonon frequencies ω_LO were determined from ?Im $\text{(}\text{1}\text{}\text{?}\text{ge}\text{)}$ of the plasmon-free phonon spectra calculated from the oscillator parameters, neglecting the free carrier contributions. The obtained effective ionic charges (Szigeti charges) reveal an increasing covalency of the pyrites in the order pnictides > chalcides and Fe > Ru > Os > Mn compounds. The phonon frequencies reflect the increasing bond strengths on going from 3d to 4d and 5d metal compounds, discussed in a former work (Phys. Chem. Miner.9, 109 (1983)). The true intensities of the phonon modes for using them with respect to lattice dynamical calculations are discussed.     

Ru(III), Os(VIII), Pd(II) and Pt(IV) catalysed oxidation of glycyl–glycine by sodium N‐chloro‐p‐toluenesulfonamide: comparative mechanistic aspects and kinetic modelling

The Ru(III)/Os(VIII)/Pd(II)/Pt(IV)‐catalysed kinetics of oxidation of glycyl–glycine (Gly‐Gly) by sodium N‐chloro‐p‐ toluenesulfonamide (chloramine‐T; CAT) in NaOH medium has been investigated at 308 K. The stoichiometry and oxidation products in each case were found to be the same but their kinetic patterns observed are different. Under comparable experimental conditions, the oxidation‐kinetics and mechanistic behaviour of Gly‐Gly with CAT in NaOH medium is different for each catalyst and obeys the underlying rate laws:

• Rate = k [CAT]_t [Gly‐Gly]⁰ [Ru(III)][OH^?]^x
• Rate = k [CAT]_t[Gly‐Gly]^x [Os(VIII)]^y[OH^?]^z
• Rate = k [CAT]_t[Gly‐Gly]^x [Pd(II)][OH^?]^y
• Rate = k [CAT]_t[Gly‐Gly]⁰ [Pt(IV)]^x[OH^?]^y

Here, and x, y, z < 1 in all the cases. The anion of CAT, CH₃C₆H₄SO₂NCl^?, has been postulated as the common reactive oxidising species in all the cases. Under comparable experimental conditions, the relative ability of these catalysts towards oxidation of Gly‐Gly by CAT are in the order: Os(VIII) > Ru(III) > Pt(IV) > Pd(II). This trend may be attributed to the different d‐electronic configuration of the catalysts. Further, the rates of oxidation of all the four catalysed reactions have been compared with uncatalysed reactions, under identical experimental conditions. It was found that the catalysed reaction rates are 7‐ to 24‐fold faster. Based on the observed experimental results, detailed mechanistic interpretation and the related kinetic modelling have been worked out for each catalyst. Copyright © 2008 John Wiley & Sons, Ltd.     

Optical and electrochemical characteristics of Ir(III) complexes with metalated 4-(4-bromophenyl)-2-methyl-1,3-thiazole and isocyanide,ethylenediamine, and diethyldithiocarbamate ligands

The influence of donor–acceptor properties of tert-butyl-, 2.6-dimethylphenyl-, and 4-bromophenyl-isocyanides (BuNC, XylNC, BpNC), ethylenediamine (En), and diethyldithiocarbamate ions (Dtc–) on the ¹H and ¹³C NMR, IR, optical, and electrochemical characteristics of Ir(III) complexes with metalated 4-(4-bromophenyl)-2-methyl-1,3-thiazole is studied. Enhancement of the donor properties of BpNC, XylNC, BuNC, En, and Dtc^– ligands leads to a bathochromic shift of metal-to-ligand charge transfer (MLCT) bands and to a decrease in the difference between the one-electron oxidation and reduction potentials of complexes. The bathochromic shift of the low-temperature phosphorescence of complexes in frozen (77 K) solutions with increasing donor properties of BpNC, XylNC, BuNC, En, and Dtc–ligands is caused by a decrease in the admixture of MLCT to the intraligand excited state of {Ir(bptz)₂}. Quenching of the phosphorescence of complexes in liquid solutions is attributed to the thermally-induced population of excited d–d* states with subsequent nonradiative deactivation.     

Specific features of the electronic structure of cerium and its 4d and 5d partners in CeM2 Laves phases (M=Fe, Co, Ni, Ru, Rh, Os, Pt, Mg, Al)

The x-ray line shift method has been used to study the electronic state of Ce (the 4f population) and of its 4d and 5d partners in the CeM₂ Laves phases (M=Fe, Co, Ni, Ru, Rh, Os, Pt, Mg, Al). It is shown that the valence of Ce in CeM₂ decreases monotonically from the limiting value m≈3.35 to m≈3 with decreasing intracrystalline compression of Ce atoms. The population of the outer 4d and 5d orbitals of Ru, Rh, and Os in the Laves phases has been found to be larger than that in metals. Fiz. Tverd. Tela (St. Petersburg) 40, 1397–1400 (August 1998)     

Photoelectron spectroscopy of molecular systems and quantum-chemical calculations in terms of the density functional theory: Iron π complexes L-Fe(CO)3

The HeI and NeI photoelectron spectra of irontricarboniyl complexes with cyclic diene ligands—αmethylstyrene, orthoquinodimethane, and cyclooctatetraene—were obtained. The results of quantum-chemical calculations of the molecules of these compounds in the approximation of the density functional theory (B3LYP/6-31G*) are presented. It is shown that this approximation describes well the excited ionic states of the π complexes under study. The relative ionization cross sections σ_π and σ_3d , which characterize the probability of removal of electrons from the molecular π-ligand and 3d-metal orbitals, are estimated. The mechanism of the selective coordination of the Fe(CO)₃ groups to corresponding organic ligands is discussed. The energies of the L-Fe(CO)₃ chemical bond are calculated.     

DFT study of electronic structure and optical properties of some Ru- and Rh-based complexes for dye-sensitized solar cells

The paper reports Time Dependent Density Functional Theory (TD DFT) calculations providing the structure, electronic properties and spectra of [Ru(II)(bpy)_{3? n} (dcbpy) _n ]²⁺ and [Rh(III)(bpy)_{3? n} (dcbpy) _n ]³⁺ complexes, where bpy?=?2,2′-bipyridyl, dcbpy?=?4,4′-dicarboxy-2,2′-bipyridyl, and n?=?0,?1,?2,?3, studied as possible pigments for dye-sensitized solar cells. The role of the metallic ion and of the COOH groups on the optical properties of these complexes are compared and contrasted and their relevance as dyes for hybrid organic–inorganic photovoltaic cells is discussed. It was found that the optical spectra are strongly influenced by the metallic ion, with visible absorption bands for the Ru(II) complexes and only ultraviolet bands for the Rh(III) complexes. Upon excitation, the extra positive charge of the Rh³⁺ centre tends to draw electrons towards the metal ion, facilitating some charge transfer from the ligand to the metal, whereas in the case of the Ru²⁺ ion the electron transfer is clearly from the metal to the ligand. The carboxyl groups play an important role in strengthening the absorption bands in solution in the visible region. Of the complexes studied, the most suited as pigments for dye-sensitized solar cells are the [Ru(II)(bpy)_{3? n} (dcbpy) _n ]²⁺ complexes with n?=?1 and 2. This is based on the following arguments: (i) their intense absorption band in the visible region, (ii) the presence of the anchoring groups allowing the bonding to the TiO₂ substrate and the charge transfer, and (iii) the good energy level alignment with the conduction band edge of the semiconducting substrate and the redox level of the electrolyte.     

Mössbauer isomer shifts and quadrupole splittings in osmium compounds

From Mössbauer spectra of the 36.2keV and 69.5keV gamma rays of¹⁸⁹Os, isomer shifts and electric quadrupole interactions for a number of chemical compounds of osmium in the oxidation states +8, +6, +4, +3, and +2 were obtained. The results show that the dependence of the isomer shifts on the oxidation state of Os follows the general pattern established for other transition elements like Ru and Ir. A comparison of the isomer shift data with electron densities at the Os nuclei resulting from relativistic self-consistentfield calculations for free Os ions yieldsΔ 〈r²〉 [36 keV]=?2.0 · 10^?3 fm² andΔ 〈r²〉 [69 keV]=?0.13 · 10^?3 fm³ for the changes of the mean-square nuclear charge radius of¹⁸⁹Os. These values are in qualitative agreement with an interpretation of the low-energy level scheme of¹⁸⁹Os in terms of two rotational bands.     

Absorption spectra of actinide compounds

From the energy levels of the gaseous ions Ac⁺⁺, Th⁺⁺⁺, and Th⁺⁺, it can safely be extrapolated that the ground electron configuration of all actinide ions with ionic charges at least + 3 contains only 5f-electrons outside the emanation shells. This is further supported by the 5fⁿ → 5f^n-16d transitions observed in Pa(IV), U(III), Np(III) (though their wave numbers are too high to be measured in U(IV) and Np(IV)). The configuration f² has a very characteristic distribution of energy levels between ³H₄ and ³P₂ with ¹S₀ as much higher, isolated level. The absorption spectra of U(IV) complexes and of PuF₆ suggest interelectronic repulsion parameters ～60 per cent of the values in the corresponding lanthanides, while the Landé factors are about twice as large. This would also explain the recent measurements of Cm(III) complexes, compared to Gd(III). The larger average radius of the 5f-shell causes larger perturbation effects from the ligands than in the lanthanides. The J-values will therefore be distributed between several adjacent, observed energy levels without making the general treatment of the fⁿ-configurations impossible. The variation with oxidation numbers in isoelectronic series are discussed, e.g. U(III) and Np(IV); Pu(III) and AmF₄; and Am(III) and CmF₄. Band positions are predicted in Bk(III) and BkF₄. Finally, the chemical properties of the actinide elements are discussed, and it is emphasized that no necessary connections exist between the presence of f-electrons and constant trivalency.     

Studies of local phase transition behavior for Co2+ in CsCaCl3 crystals from EPR data

In this paper, we establish the calculation formulas ofg factorsg _∥,g _⊥ and the hyperfine structure constantsA _∥,A _⊥ for 3d⁷ ions in tetragonal octahedral field from a cluster approach. In these formulas, besides the configuration interaction, the covalency effect due to the admixture between d electrons of 3d⁷ ion and the p electrons of ligands is considered. The parameters used in these formulas (except the core polarization constantsk in the calculation ofA _i) can be obtained from optical spectra of the studied crystal. From these formulas, the local release (or elongation) factork, which is introduced to characterize the release effect of impurity-ligand bond along C₄ axis at the cubic to tetragonal phase transition, is estimated for CsCaCl₃:Co²⁺ crystal by calculating the electronic paramagnetic resonance (EPR) parametersg _i andA _i . These EPR parameters are therefore explained reasonably and the results are discussed.     

Microstructured hydroxyl environments and Raman spectroscopy in selected basic transition-metal halides

Raman vibrational spectra of the selected basic (hydroxyl OH and deuteroxyl OD) transition-metal halides, geometrically frustrated material series α-, β-, γ-Cu₂(OH)₃Cl, α-Cu₂(OH)₃Br, β-Ni₂(OH)₃Cl, β-Co₂(OH)₃Cl, β-Co₂(OH)₃Br, γ-Cu₂(OD)₃Cl, and β-Co₂(OD)₃Cl are measured at room temperature and analysed to investigate the relationship between the microstructured OH environments and their respective Raman spectra. Among these selected samples, the last two are used to determine the OH stretching vibration region (3600 cm^-1—3300 cm^-1) and OH bending vibration region (1000 cm^-1—600 cm^-1) of OH systems in the spectra. Through the comparative analysis of the distances d(metal—O), d(O—halogen), and d(OH), the strong metal—O interaction and trimeric hydrogen bond (C_3v, C_s or C₁ symmetry) are found in every material, but both determine simultaneously an ultimate d(OH), and therefore an OH stretching vibration frequency. According to the approximately linear relationship between the OH stretching vibration frequency and d(OH), some unavailable d(OH) are guessed and some doubtful d(OH) are suggested to be corrected. In addition, it is demonstrated in brief that the OH bending vibration frequency is also of importance to check the more detailed crystal microstructure relating to the OH group.     

Strong spin-dependent absorption at theL 2,-edges of 5d-impurities in iron

Large spin-dependent absorption effects have been observed with circularly polarized photons of energies between 10.8 keV and 13.8 keV at theL _2,3-edges of Os, Ir, Pt, and Au impurities (3 at.%) in iron. The largest value of the spin-dependent absorption coefficient (µ _c /µ _o +0.22) is found at the PtL ₂-edge. From the energy dependence of the spin-dependent absorption at theL ₂- andL ₃-edges the spin-density profiles of thed _3/2-andd _5/2-projected states populated in the absorption process are derived. Thed _5/2-spin densities deduced from theL ₃ spin-dependent absorption spectra agree well with spin-polarized band-structure calculations for the ferromagnetic ground state. A comparison of thed _3/2- andd _5/2-spin densities shows a strong contribution of the spin-orbit effects to the exchange splitting in Os, whereas only small spin-orbit effects are indicated for Ir, Pt and Au impurities.     

High-spin negative parity states in doubly even Hg,Pt and Os nuclei

A systematic study of the level structure of ²⁰⁰Hg, ¹⁹⁸Hg, ¹⁹⁶Hg, ¹⁹⁴Pt, ¹⁹²Pt, ¹⁹⁰Pt, ¹⁸⁸Os, ¹⁸⁶Os and ¹⁸⁴Os has been performed by means of (α, 2nγ) and (p, 2nγ) in-beam γ-ray spectroscopy. Much new information has been obtained about the individual level spectra, and arguments based on level energy and population intensity systematics have been used to trace the behaviour of interesting spectral features through this series of transitional nuclei. Of particular interest is a 5^?, 7^?, 9^? … sequence of levels which appears to be a recurring feature in the spectra of the doubly even Pt and Hg nuclei in the mass range A = 190–200. These negative parity levels are connected by enhanced E2 transitions and they are very strongly populated in the de-excitation of the residual nuclei formed in (α, 2n) reactions. It is proposed that the 5^?, 7^?, 9^? … sequences constitute rotation-aligned bands analogous to the decoupled bands identified by Stephens and co-workers in odd-A transitional nuclei. In the doubly even nuclei, the bands may arise from the coupling of an $\text{i}\text{13}\text{2}$ neutron with a low-j neutron partner (from the $\text{p}{}_{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}$, $\text{p}{}_{\mathrm{<mtext>3</mtext><mtext>2</mtext>}}$ and $\text{f}{}_{\mathrm{<mtext>5</mtext><mtext>2</mtext>}}$ orbitals). Negative parity levels in the Os nuclei are populated much less strongly in the (α, 2nγ) reactions. While 5^? levels corresponding to those in the Pt and Hg nuclei appear to be fairly well established in ¹⁸⁶Os, ¹⁸⁸Os (and ¹⁹⁰Os), it is not yet clear whether the 5^?, 7^?, 9^? … band sequence extends into the Os nuclei.     

Energy band structure and X-ray emission spectra of ZrC and ZrN

Self-consistent augmented plane wave calculations are performed for ZrC and ZrN. The charge distributions resulting from valence bands in different regions of the unit cell are discussed and compared with related compounds, where the transition metal is varied between a 3d and 4d element of group IV and V. The limitations of the rigid band model are illustrated and general trends in the chemical bonding are discussed. In connection with X-ray emission spectra (XES) matrix element effects are shown for the three spectra Zr-L_III,-M_III, and-N_III. Further, comparison between theoretical and experimental XES is made with all data available for both ZrC and ZrN.     

Chemical tuning of high-spin complexes based on 3- and 4-hydroxy-pentadentate-Fe (III) complex-units investigated by Mössbauer spectroscopy

The pentadentate ligands 3-OH-⁵L?=?[N,N′-Bis(1,3-dihydroxy-2-benzylidene)-1,7-diamino-4-azaheptane] and 4-OH-⁵L?=?[N,N′-Bis(1,4-dihydroxy-2-benzylidene)-1,7-diamino-4-azaheptane] has been prepared by a Schiff base condensation between 1,7-diamino-4-azaheptane and the dihydroxybenzaldehyde. Complexation with Fe(III) yields high-spin (S?=?5/2) complexes of [Fe^III(3-OH-⁵L)Cl] and [Fe^III(4-OH-⁵L)Cl]. These precursors were combined with [M(CN) _x ] ^y? (M?=?W(IV), Mo(IV), Ru(II), Co(III)) and heptanuclear and nonanuclear clusters of [M{(CN-Fe^III(3-OH-⁵L)} _x ]Cl _y and [M{(CN-Fe^III(4-OH-⁵L)} _x ]Cl _y resulted. Such starshaped hepta- and nonanuclear compounds are high-spin systems at room temperature. On cooling to 10 K some of the iron(III) centers switch to a second high-spin state as proven by Mössbauer spectra, i.e. multiple electronic transitions. Parts of the compounds perform a high-spin to high-spin transition.     

New red electrophosphor based on Ir(III) complex of 2,3,4-triphenylquinoline

2,3,4-Triphenylquinoline (tpq) ligand and its Ir(III) complex Ir(tpq)₂(acac) were prepared and their photonic properties were investigated as red electrophosphorescent material. The photoluminescence (PL) spectra of tpq and Ir(tpq)₂(acac) in dichloromethane showed a peak at 450 nm and 607 nm, respectively, at room temperature. The small Stokes shift between the ³MLCT absorption and emission bands shows that Ir(tpq)₂(acac) emits from a predominantly ³MLCT excited state. The theoretical calculation of the Ir(III) complex was performed by an ab initio method, and the result calculated by time dependent density functional theory (TD-DFT) showed that the Ir(III) complex underwent a strong ³MLCT transition because of the strong coupling between the 5d-orbital of Ir atom and the highest occupied molecular orbital (HOMO) of tpq ligand. Thus, it is concluded that this complex is a good candidate for a highly efficient electrophosphorescent material.     

BaxOy小团簇修饰Ru(0001)表面的结构稳定性和氮分子吸附性质

为了说明钡助剂的存在形式, 本文采用第一性原理方法研究了Ba_xO_y小团簇修饰Ru(0001)表面的结构稳定性和氮分子吸附性质. 基于总能的热力学分析发现, 在实验条件下(500 K, P_H2O/P_H2<10^-3), Ba₂O团簇比BaO₂, BaO, Ba和O等团簇(原子)更加稳定. 这证实含有金属性钡原子的团簇也是氧化钡助剂可能的工作状态. 表面电荷差分密度说明Ba₂O团簇的氧和钡原子与衬底的作用不同. 不过Ba₂O团簇氧和钡原子附近的氮分子吸附行为相似, Ba₂O团簇增强了氮分子和衬底的相互作用. Ba₂O团簇氧和钡原子附近的氮分子吸附能分别为0.78 和0.88 eV, 均大于清洁表面的0.67 eV. 氮分子间距和氮分子的拉伸振动频率都表明Ba₂O团簇在一定程度上活化了吸附氮分子. Ba₂O团簇氧和钡原子附近的N–N键长分别为0.117和0.116 nm, 大于清洁表面的0.114 nm. 氧和钡原子附近氮分子的拉伸振动频率分别为 1888 和1985 cm^-1, 小于清洁表面的2193 cm^-1. 电荷差分密度的计算结果说明, 削弱作用主要来自于Ba₂O团簇中钡离子和氮分子间的静电作用. 两者间的静电作用增加了氮分子π 反键轨道的占据数, 促进了氮分子极化, 从而削弱氮分子键.     

Optical absorption edge of Cd1−x Mn x Ga2Se4 crystals

Summary We report the absorption edge spectra of the new family of diluted magnetic semiconductors Cd_1−x Mn _x Ga₂Se₄ (0≤x≤1), grown from the vapour phase by chemical transport. Absorption bands observed under the gap of CdGa₂Se₄ are attributed to intra-Mn²⁺ transitions involving excited states of the 3d ⁵ electrons, split by the crystal field. The authors of this paper have agreed to not receive the proofs for correction.