Chromium‐based clinopyroxene‐type germanates NaCrGe2O6 and LiCrGe2O6 at 298 K

The structure analyses of sodium chromium digermanate, NaCrGe₂O₆, (I), and lithium chromium digermanate, LiCrGe₂O₆, (II), provide important structural information for the clinopyroxene family, and form part of our ongoing studies on the phase transitions and magnetic properties of clinopyroxenes. (I) shows C2/c symmetry at 298 K, contains one Na, one Cr (both site symmetry 2 on special position 4e), one Ge and three O‐atom positions (on general positions 8f) and displays the well known clinopyroxene topology. The basic units of the structure of (I) are infinite zigzag chains of edge‐sharing Cr³⁺O₆ octahedra (M1 site), infinite chains of corner‐sharing GeO₄ tetrahedra, connected to the M1 chains by common corners, and Na sites occupying interstitial space. (II) was found to have P2₁/c symmetry at 298 K. The structure contains one Na, one Cr, two distinct Ge and six O‐atom positions, all on general positions 4e. The general topology of the structure of (II) is similar to that of (I); however, the loss of the twofold symmetry makes it possible for two distinct tetrahedral chains, having different conformation states, to exist. While sodium is (6+2)‐fold coordinated, lithium displays a pure sixfold coordination. Structural details are given and chemical comparison is made between silicate and germanate chromium‐based clinopyroxenes.     

Strontium magnesium phosphate,Sr2+xMg3−xP4O15 (x∼ 0.36), from laboratory X‐ray powder data

The previously unknown crystal structure of strontium magnesium phosphate, Sr_2+xMg_3−xP₄O₁₅ (x∼ 0.36), determined and refined from laboratory powder X‐ray diffraction data, represents a new structure type. The title compound was synthesized by high‐temperature solid‐state reaction and it crystallizes in the orthorhombic space group Cmcm. It was earlier thought to be stoichiometric Sr₂Mg₃P₄O₁₅, but our structural study indicates the nonstoichiometric composition. The asymmetric unit contains one Sr (site symmetry ..m on special position 8g), one M (= Mg 64%/Sr 36%; site symmetry 2/m.. on special position 4b), one Mg (site symmetry 2.. on special position 8e), two P (site symmetry m.. on special position 8f and site symmetry ..m on special position 8g), and six O sites [two on general positions 16h, two on 8g, one on 8f and one on special position 4c (site symmetry m2m)]. The nonstoichiometry is due to the mixing of magnesium and strontium ions on the M site. The structure consists of three‐dimensional networks of MgO₄ and PO₄ tetrahedra, and MO₆ octahedra with the other strontium ions occupying the larger cavities surrounded by ten O atoms. All the polyhedra are connected by corner‐sharing except the edge‐sharing MO₆ octahedra forming one‐dimensional arrangements along [001].     

Symmetry breaking and electron correlation in O2−, O2, and O2+: A comparison of coupled cluster and quadratic configuration interaction approaches

Potential energy curves are calculated for O₂⁻, O₂, and O₂⁺ at the CCSD, QCISD, CCSD(T), and QCISD(T) levels of theory using aug-cc-pVDZ and aug-cc-pVTZ basis sets with electron correlation built onto inversion symmetry constrained and relaxed UHF wave functions. The spectroscopic constant r_e, w_e, w_e, x_e, D_j, and α_e, are determined from the potential curves using standard second-order perturbation theory expressions and are compared with experimental values to assess the relative accuracy of the theoretical approaches. Comparison of corresponding symmetry-constrained and symmetry-relaxed calculations indicates that the CCSD method is generally superior to CCSD(T), QCISD, and QCISD(T) in recovering from a symmetry-broken reference function. © 1996 John Wiley & Sons, Inc.     

Synthesis of 2-aryl-4-(4-<Emphasis Type="Italic">β</Emphasis>-D-allopyranosyloxyphenyl)4,6,7,8-tetrahydroquinolin-5(1<Emphasis Type="Italic">H</Emphasis>)-one derivatives under solvent-free conditions and study of sedative activity

Under solvent-free conditions, syntheses of 2-aryl-4-(4-β-D-allopyranosyloxyphenyl)-4,6,7,8tetrahydroquinolin-5(1H)-one derivatives were carried out from chalcone (2a–2e), cyclohexane-1,3-dione (3), and NH₄OAc in excellent yield without using any catalysts. The structure of the new compounds were characterized by ¹H NMR, IR, and HR-MS spectroscopy. The preliminary bioassay tests of 4a–4j indicated that compounds 4b, 4e, and 4f exhibited potent sedative and hypnotic activity.     

Synthesis and liquid crystal properties of a new class of calamitic mesogens based on substituted 2,5‐diaryl‐1,3,4‐thiadiazole derivatives with wide mesomorphic temperature ranges

Liquid crystals based on substituted 2,5‐diaryl‐1,3,4‐thiadiazole derivatives (1a–1f, 3a and 3b) and 1,3,4‐oxadiazole analogues (2a–2f, 4a and 4b) were synthesised and characterised by ¹H, ¹³C nuclear magnetic resonance, Fourier transform infrared, mass spectrometry, high‐resolution mass spectrometry techniques and elemental analyses. The X‐ray crystal structure of 1e revealed that it contains tilted lamellar arrangement of molecules in the crystalline solid. The liquid crystal properties have been investigated by polarised‐light optical microscopy, differential scanning calorimetry and in‐situ variable‐temperature X‐ray diffraction. All compounds (except 2e and 2f) exhibited thermotropic liquid crystal behaviours with various mesophases (smectic A and C, nematic N or soft crystal E phases). Notably, the 1,3,4‐thiadiazole derivatives consistently have wider mesomorphic temperature ranges than those of the respective 1,3,4‐oxadiazole analogues. The solutions of all compounds in CH₂Cl₂ individually displayed one or two absorption bands with λ _max values at 297–355 nm and emitted with λ _max values at 363–545 nm and quantum yields of 0.12–0.73. Structure–property relationships of these compounds are discussed in the contexts of their molecular structures and weak intermolecular interactions.     

Ionic bonding of lanthanides,as influenced by d‐ and f‐atomic orbitals,by core–shells and by relativity

Lanthanide trihalide molecules LnX₃ (X = F, Cl, Br, I) were quantum chemically investigated, in particular detail for Ln = Lu (lutetium). We applied density functional theory (DFT) at the nonrelativistic and scalar and SO‐coupled relativistic levels, and also the ab initio coupled cluster approach. The chemically active electron shells of the lanthanide atoms comprise the 5d and 6s (and 6p) valence atomic orbitals (AO) and also the filled inner 4f semivalence and outer 5p semicore shells. Four different frozen‐core approximations for Lu were compared: the (1s²–4d¹⁰) [Pd] medium core, the [Pd+5s²5p⁶ = Xe] and [Pd+4f¹⁴] large cores, and the [Pd+4f¹⁴+5s²5p⁶] very large core. The errors of Lu? X bonding are more serious on freezing the 5p⁶ shell than the 4f¹⁴ shell, more serious upon core‐freezing than on the effective‐core‐potential approximation. The Ln? X distances correlate linearly with the AO radii of the ionic outer shells, Ln³⁺‐5p⁶ and X^?‐np⁶, characteristic for dominantly ionic Ln³⁺‐X^? binding. The heavier halogen atoms also bind covalently with the Ln‐5d shell. Scalar relativistic effects contract and destabilize the Lu? X bonds, spin orbit coupling hardly affects the geometries but the bond energies, owing to SO effects in the free atoms. The relativistic changes of bond energy BE, bond length R_e, bond force k, and bond stretching frequency v_s do not follow the simple rules of Badger and Gordy (R_e～BE～k～v_s). The so‐called degeneracy‐driven covalence, meaning strong mixing of accidentally near‐degenerate, nearly nonoverlapping AOs without BE contribution is critically discussed. © 2015 Wiley Periodicals, Inc.     

Darstellung,Kristallstrukturen, Schwingungsspektren und Normalkoordinatenanalysen der Tetrahalogeno‐bis‐Pyridin‐Osmium(III)‐Komplexe cis‐(n‐Bu4N)[OsCl4Py2] und trans‐(n‐Bu4N)[OsX4Py2], X = Cl,Br

Synthesis, Crystal Structures, Vibrational Spectra, and Normal Coordinate Analyses of the Tetrahalogeno‐bis‐Pyridine‐Osmium(III) Complexes cis ‐( n ‐Bu₄N)[OsCl₄Py₂] and trans ‐( n ‐Bu₄N)[OsX₄Py₂], X = Cl, Br By reaction of (n‐Bu₄N)₂[OsX₆], X = Cl, Br, with pyridine and (n‐Bu₄N)[BH₄] tetrahalogeno‐bis‐pyridine‐osmium(III) complexes are formed and purified by chromatography. X‐ray structure determinations on single crystals have been performed of cis‐(n‐Bu₄N)[OsCl₄Py₂] ( 1 ) (triclinic, space group P1, a = 9.4047(9), b = 10.8424(18), c = 17.007(2) Å, α = 71.833(2), β = 81.249(10), γ = 67.209(12)°, Z = 2), trans‐(n‐Bu₄N)[OsCl₄Py₂] ( 2 ) (orthorhombic, space group P2₁2₁2₁, a = 8.7709(12), b = 20.551(4), c = 17.174(4) Å, Z = 4) and trans‐(n‐Bu₄N)[OsBr₄Py₂] ( 3 ) (triclinic, space group P1, a = 9.132(3), b = 12.053(3), c = 15.398(2) Å, α = 95.551(18), β = 94.12(2), γ = 106.529(19)°, Z = 2). Based on the molecular parameters of the X‐ray structure determinations and assuming C₂ point symmetry for the anion of 1 and D_2h point symmetry for the anions of 2 and 3 the IR and Raman spectra are assigned by normal coordinate analysis. The valence force constants of 1 are in the Cl–Os–Cl axis f_d(OsCl) = 1.58, in the asymmetrically coordinated N′–Os–Cl ^· axes f_d(OsCl ^· ) = 1.45, f_d(OsN′) = 2.48, of 2 f_d(OsCl) = 1.62, f_d(OsN) = 2.42 and of 3 f_d(OsBr) = 1.39 and f_d(OsN) = 2.34 mdyn/Å.     

Threshold voltage for purely flexoelectric deformations of conducting homeotropic nematic layers

Elastic deformations induced by an electric field in homeotropic nematic layers with finite anchoring energy were studied numerically. A nematic material possessing flexoelectric properties and characterized by a positive dielectric anisotropy was considered. The ionic space charge and the ion transport across the layer were taken into account. The director orientation, the electric field strength and the ion concentrations were calculated as functions of the coordinate normal to the layer. The calculations show that the electric field distribution, which determines the form of the deformations, is influenced by the ionic current and therefore depends on the ionic content and on the properties of the electrodes. Several types of deformations were distinguished. When the electrode contacts are well conducting or when the ionic content is low, the threshold voltage is very close to the value U _f valid for an insulating nematic. When the electrodes are poorly conducting or blocking at high ion concentration, the threshold voltage decreases much below U _f. At moderate ion concentrations, i.e. between 10¹⁹ and 10²⁰ m^?3, two different behaviours were found depending on the sign of the sum of flexoelectric coefficients e ₁₁+e ₃₃. In the case of e ₁₁+e ₃₃<0, the threshold voltage decreases with the ionic content; in the case of e ₁₁+e ₃₃>0, the deformations occur in two separate voltage regimes. They arise above a certain threshold voltage, disappear at some higher voltage and reappear at an even higher threshold.     

Darstellung,Kristallstrukturen, Schwingungsspektren und Normalkoordinatenanalysen der mer‐Trihalogeno‐tris‐Pyridin‐Osmium(III)Komplexe mer‐[OsX3Py3], X = Cl,Br, I

Synthesis, Crystal Structures, Vibrational Spectra, and Normal Coordinate Analyses of the mer ‐Trihalogeno‐tris‐Pyridine‐Osmium(III) Complexes mer‐[OsX₃Py₃], X = Cl, Br, I By reaction of the hexahalogenoosmates(IV) with pyridine and iso‐amylalcohol mer‐trihalogeno‐tris‐pyridine‐osmium(III) complexes are formed and purified by chromatography. X‐ray structure determinations on single crystals have been performed of mer‐[OsBr₃Py₃] (monoclinic, space group P2₁/n, a = 9.098(5), b = 12.864(5), c = 15.632(5) Å, β = 90.216(5)°, Z = 4) and mer‐[OsI₃Py₃] (monoclinic, space group P2₁/n, a = 9.0952(17), b = 13.461(4), c = 15.891(10), β = 91.569(5)°, Z = 4). The pyridine rings are twisted propeller‐like against the N₃ meridional plane with mean angles of 49° (Cl), 46° (Br), 44° (I). Based on the molecular parameters of the X‐ray structure determinations and assuming C₂ point symmetry, the IR and Raman spectra are assigned by normal coordinate analysis. Due to the stronger trans influence of pyridine as compared with the halide ligands for N'–Os–X ^· axes significantly different valence force constants are observed in comparison with symmetrically coordinated octahedron axes: f_d(OsCl) = 1.74, f_d(OsCl^·) = 1.49, f_d(OsBr) = 1.43, f_d(OsBr ^· ) = 1.18, f_d(OsI) = 0.99, f_d(OsI ^· ) = 0.96, f_d(OsN) between 1.96 and 2.07 and f_d(OsN') between 2.13 and 2.32 mdyn/Å.     

Systematic investigation of the influence of methyl groups upon fluorescence parameters and the intersystem crossing rate constant of aromatic molecules

The absorption and fluorescence properties of 29 specially selected methyl substituted benzene, naphthalene, anthracene, biphenyl, fluorene and p-oligophenylenes compounds are studied experimentally (at 293 K) and quantum-chemically. The fluorescence quantum yield, γ, and decay times, τ_f, for deaerated and non-deaerated solutions were measured. The oscillator strength, f_e, natural lifetime, and fluorescence and intersystem crossing rate constants, k_f and k_ST, respectively, are calculated for each compound. The orbital nature of the lowest excited singlet state, S¹, is determined. The investigation shows that the introduction of methyl groups onto aromatic compounds may produce different effects. For example, the symmetry and hence k_ST and k_f may change. As a result, γ will also change. Steric hindrance, caused by the CH₃ group(s) will decrease k_f while increasing k_ST. In cases where the introduction of the methyl group leaves the symmetry unchanged, there is a slight increase in k_ST but a slight decrease in k_f. This effect is cumulative (more CH₃ groups lead to a greater decrease in γ) and is attributable to the torsional vibrations of the methyl groups. Cases where introduction of CH₃ group(s) causes the inversion of ¹L_a and T_β levels are observed and explained. Such inversion is accompanied by the increase in k_f and sometimes, by the significant decrease in k_ST, which leads to a dramatic increase in the fluorescence quantum yield. Such changes improve laser properties or can convert a non-lasing compound to a lasing one. It is predicted that the CH₃ group(s) can cause the inversion of ¹L_a and ¹L_a or and levels, which can change the nature of fluorescence or can change a nonfluorescent compound to a fluorescent one. The trends observed may be used to change fluorescence properties of an aromatic compound in the necessary direction without changing its π-system.     

Dihydroxyacetone (DHA) monomer complexes with CaBr2 and CdCl2

Two hydrated complexes of monomeric dihydroxyacetone (DHA; the simplest ketose), viz. the calcium bromide complex bis(μ‐dihydroxyacetone)bis[tetraaquacalcium(II)] tetrabromide (isomorphous with the chloride compound reported previously), [Ca₂(C₃H₆O₃)₂(H₂O)₈]Br₄, (2e), and the cadmium chloride complex poly[[bis(μ‐dihydroxyacetone)bis[bis(dihydroxyacetone)cadmium(II)]] [diaquatetradeca‐μ‐chlorido‐dichloridohexacadmium(II)] tetrahydrate], {[Cd₂(C₃H₆O₃)₆][Cd₆Cl₁₆(H₂O)₂]·4H₂O}_n, (2f), are described. The Ca²⁺ or Cd²⁺ ions are bridged by the carbonyl O atoms from two DHA molecules to form centrosymmetric dimers, with Ca...Ca distances of 4.334 (2) and 4.300 (2) Å in (2e), and a Cd...Cd distance of 4.195 (1) Å in (2f). Almost identical in shape, the eight‐coordinate polyhedra of the Ca²⁺ and Cd²⁺ ions are composed of 2n O atoms from n DHA molecules [n = 2 in (2e) and n = 4 in (2f)] and are completed by four water molecules in (2e). DHA molecules chelate the cations via both the hydroxyl and carbonyl groups and exist in an extended conformation, with both hydroxyl groups being synperiplanar to the carbonyl O atom. The crystal structures are stabilized by similar extensive O—H...X (X = Cl or Br) and O—H...O hydrogen‐bond networks involving all hydroxyl groups and the water molecules.     

A new synthetic cobalt tellurate: Co3TeO6

Single crystals of tricobalt(II) tellurium(VI) hexa­oxide, Co₃TeO₆, were synthesized via transport reactions using HCl as transporting agent. The compound crystallizes in the monoclinic system (space group C2/c). The Te atoms are positioned in 4b () and 8f positions, while the Co atoms are in 4e (2) and 8f positions. The structure consists of (100) oxygen layers packed in a hhchhc sequence, with Te^VI in octa­hedral coordination and Co^II in both octa­hedral and tetra­hedral coordination. The structure contains face‐sharing CoO₆ octa­hedra, as well as edge‐sharing CoO₄ tetra­hedra. Co₃TeO₆ is the first oxide that is isostructural with the β‐Li₃MF₆ family of compounds (M = Al, Cr, Ga, Ti and V).     

A new approach to electron diffraction analysis of symmetric triatomic molecules with large-amplitude bending motion: The equilibrium geometry,force field and vibrational frequencies of BaI2 as determined by electron diffraction

Diffraction data on BaI₂, analyzed by a new approach, indicate an anharmonic potential with a barrier of 71(12) cm^?1 at a linear geometry. The structural and vibrational parameters were found to be r_e^h(Ba-I_o) = 3.150(7)Å, ∠_eIBaI = 148.0(9) °, f_q = 0.69(8) mdyn/Å,f_qq= 0.14(6) mdyn/Å, k₂ = ?0.0075(15) mdyn/Å, k₄ = 0.0025(9) mdyn/ų, v₁ = 106(12) cm^?1 and v₃ = 145(21) cm^?1. The bending frequency v₂ is predicted to be near 16 cm^?1.     

The Isomeric Composition of D-Xylo-hexos-5-ulose (5-Keto-glucose) in Aqueous Solution

Abstract

1,2-O-Isopropylidene-α-D-xylo-hexofuranos-5-ulose (2) was deprotected in aqueous acid solution to give a mixture of at least six isomeric forms and one anhydro form of the parent ketoaldohexose, D-xylo-hexos-5-ulose (3), commonly referred to as 5-keto-glucose. Structural assignment of each form was made based on high field ¹H and ¹³C NMR studies of the mixture in aqueous (D₂O) solution. The dominant isomeric form of 3 was observed to have the pyranose structure 1R,5R-D-xlyo-hexo-pyranos-5-ulose (3a, 67 %) with the next most abundant form being an anhydro structure, 1S,5S-l,6-anhydro-D-xylo-hexopyranos-5-ulose (3c, 18 %). Included among the other isomers were the a and β-1,4-furanose (3d, 3e) and 1-aldehydrol β-5,2-furanose (3f) structures. The isomer present in least amount (3g, > 1 %) is assigned as the α-anomer of 3f. Experimentally determined J_C-1,H-1 values were useful in support of assigned isomer structures.     

Contraction of the well-tempered Gaussian basis sets: The first-row diatomic molecules

The well-tempered Gaussian basis sets (14s 10p) for atoms from lithium to neon were contracted and used in restricted Hartree–Fock calculations on 13 systems: Li₂(Σ), B₂(Σ), C₂(Σ), N₂(Σ), O₂(Σ), F₂(Σ), Ne₂(Σ), LiF(Σ), BeO(Σ), BF(Σ), CN^?(Σ), CO(Σ), and NO⁺(Σ). Spectroscopic constants (R_e, ω_e, ω_ex_e, B_e, α_e, and k_e) and one-electron properties (dipole, quadrupole, and octupole moments at the center of mass and electric field, electric field gradient, potential, and electron density at the nuclei) were evaluated and compared with the Hartree–Fock results. The largest contracted basis set (7_s6_p3_d) gives results very close to the Hartree–Fock values; the remaining differences are attributed to the absence of the f functions in the present basis sets. For Ne₂, the interaction energy was calculated; the magnitude of the basis-set superposition error was found to be very small (less than 3 μE_h at 2.8 a₀ and less than 2 μE_h at 5.0 a₀).     

Theoretical study of spectroscopic and molecular properties of several low‐lying electronic states of CO molecule

The potential energy curves (PECs) of eight low‐lying electronic states (X¹Σ⁺, a³Π, a′³Σ⁺, d³Δ, e³Σ^?, A¹Π, I¹Σ^?, and D¹Δ) of the carbon monoxide molecule have been studied by an ab initio quantum chemical method. The calculations have been performed using the complete active space self‐consistent field method, which is followed by the valence internally contracted multireference configuration interaction (MRCI) approach in combination with the correlation‐consistent aug‐cc‐pV5Z basis set. The effects on the PECs by the core‐valence correlation and relativistic corrections are included. The way to consider the relativistic corrections is to use the third‐order Douglas–Kroll Hamiltonian approximation at the level of a cc‐pV5Z basis set. Core‐valence correlation corrections are performed using the cc‐pCVQZ basis set. To obtain more reliable results, the PECs determined by the MRCI calculations are corrected for size‐extensivity errors by means of the Davidson modification (MRCI+Q). The spectroscopic parameters (D_e, T_e, R_e, ω_e, ω_ex_e, ω_ey_e, B_e, α_e, and γ_e) of these electronic states are calculated using these PECs. The spectroscopic parameters are compared with those reported in the literature. Using the Breit–Pauli operator, the spin–orbit coupling effect on the spectroscopic parameters is discussed for the a³Π electronic state. With the PECs obtained by the MRCI+Q/aug‐cc‐pV5Z+CV+DK calculations, the complete vibrational states of each electronic state have been determined. The vibrational manifolds have been calculated for each vibrational state of each electronic state. The vibrational level G(ν), inertial rotation constant B_ν, and centrifugal distortion constant D_ν of the first 20 vibrational states when the rotational quantum number J equals zero are reported and compared with the experimental data. Comparison with the measurements demonstrates that the present spectroscopic parameters and molecular constants determined by the MRCI+Q/aug‐cc‐pV5Z+CV+DK calculations are both reliable and accurate. © 2012 Wiley Periodicals, Inc.     

Scalar and quadrupolar intensity contributions in two-photon hyperfine structure transitions in europium

Two-photon transitions from the Eu I ground state 4f ⁷ 6s ² a ⁸ S _7/2 to odd levels with alsoJ=7/2 in the energy range of 34,000 – 36,700 cm^–1 were analysed due to their scalar and quadrupolar contributions. Their ratioR (g, e) were determined experimentally. In most cases the quadrupole contributions are dominant, i.e. 0R (g, e) _exp <>^–3. In the two-photon transition to the level 4f ⁷ 5d ^{2 8} F _7/2 the ratio is remarkably strong:R (g, e) _exp =134 (4)·10^–3. A theoretical estimation ofR (g, e) is not yet satisfying, due to strong configuration mixing in Eu.     

Lanthanide chelates of fluorinated β-diketones. Part III. Mass spectra of lanthanide chelates of five fluorinated β-diketones

Summary The mass spectra of sixty lanthanide chelates of the fluorinated -diketones RC(OH)=CHCOCF₃ (R=2-theonyl,p-BrC₆H₄,m-MeC₆H₄,o-MeC₆H₄, and Bu-t) have been obtained. The mass spectra were essentially similar, in contrast to those found ford-block transition metal chelates. Valency change from 3 to 2 occurred with samarium (4f ⁵), europium (4f ⁶), thulium (4f ¹²), and ytterbium (4f ¹³); the intensity of the Met(II)-containing peaks varied: Eu Sm > Yb > Tm, reflecting the decreasing tendency of these lanthanides to display bivalency. Valency change from 4 to 3 was observed with cerium (4f¹) but not with terbium (4f⁸).Part II,Transition Met. Chem., 9, 423 (1984).     

Kristallstruktur,Schwingungsspektren und Normalkoordinatenanalyse von K2[IrCl5(NH3)]

Crystal Structure, Vibrational Spectra, and Normal Coordinate Analysis of K₂[IrCl₅(NH₃)] The X-ray structure determination of K₂[IrCl₅(NH₃)] (orthorhombic, space group Pnma, a = 13.426(4), b = 10.015(2), c = 6.8717(7) Å, Z = 4) revealed the C_s point symmetry of the complex anion [IrCl₅(NH₃)]^2? (Ir? Cl = 2.337–2.365, Ir? N = 2.067(10); N? H = 0.73–0.79 Å). Using the molecular parameters the IR and Raman spectra are assigned by normal coordinate analysis. The valence force constants are f_d(NH) = 5.88, f_d(IrN) = 2.66, f_d(IrCl) = 1.68 mdyn/Å.     

Revisiting the nature of the ZnO ground state: Influence of spin–orbit coupling

Relativistic calculations of the low-lying electronic states of the ZnO molecule are performed for the Λ–Σ states, ¹Σ⁺, ¹Π, ¹Δ, ³Π and ³Σ⁻, at the CCSD(T) or MRCI level, using scalar relativistic energy-consistent pseudopotentials, and the EPCISO method for spin–orbit CI coupling. The ZnO ground state is assigned to 0⁺ symmetry and has ¹Σ⁺ character around the equilibrium region. The spectroscopic constants (r_e, ω_e) of the 0⁺ ground state are in good agreement with experimental results. Interpenetration of the vibrational levels of the two lowest 0⁺ states is also shown.