Hyperfine splitting of the odd 4 F J o , 2 P J o and 4 S J o LaI multiplets

High resolution spectra of LaI lines recorded in the R6G region by laser-induced resonance fluorescence method show well resolved hyperfine structures. The analysis of the hyperfine structure of seven LaI transitions is presented here. It has allowed the deduction of magnetic dipole and electric quadrupole constants of all levels belonging to the excited odd parity multiplets: ⁴ F ^o (J = 3/2-9/2), ² P ^o (J = 1/2,3/2), and ⁴ S ^o (J = 3/2). Some of the results are new and some of them present improved values of the hyperfine splitting constants.     

Large-scale MCHF calculations of hyperfine structures in nitrogen and oxygen

The hyperfine structure constants for the 1s ²2s ²2p ³ -⁴ S ^o ground state in nitrogen and the 1s ²2s ²2p ³3s ⁵ S ^o excited state in oxygen are calculated using the MCHF Atomic Structure Package. The single excitation picture is explored through the use of compact wave functions allowing radial non-orthogonalities. Electron correlation is described through numerical multiconfiguration Hartree-Fock calculations for configuration expansions obtained by allowing all single and double excitations from the reference configuration to an active set of orbitals. The latter is increased in a systematic way allowing the convergence of the hyperfine parameters to be studied. Three- and four-particle effects are shown to be important and are taken into account in a sequence of large configuration interaction calculations. The final results are in good agreement with experiment.     

Study of electron spin crossover in iron(III) tris-dithiocarbamate complexes by carbon-13 NMR spectroscopy

¹³C and ¹H isotropic shifts have been measured for a series of Fe(III) tris-dithiocarbamate complexes. The ¹³C isotropic shifts may be interpreted as arising solely from contact hyperfine coupling and demonstrate that as the low-spin state of the metal is favoured there is an increase in metal-ligand π-bonding. σ-delocalization of unpaired spin density is more important in determining the ¹³C isotropic shifts than those of the contiguous proton.     

1H and 13C endor on phenoxyl biradicals randomly oriented in frozen solution

ENDOR measurements have been performed on ¹³C labelled biradicals, namely Yang's biradical and p-phenylenebisgalvinoxyl, in frozen solutions. Besides intense ENDOR lines at the free nuclear Zeeman frequencies, hyperfine shifted ¹H and ¹³ ENDOR lines could be detected with excellent signal-to-noise ratios. From these spectra not only the magnitudes, but also the signs of the hyperfine splitting components relative to the zero field splitting parameter D could be derived. It is demonstrated that the sign of D in Yang's biradical must be negative. This may be due to a spin-orbit coupling contribution to the zero field splitting parameter.     

Electric dipole moment of the diatomic AgBr molecule

Stark effect measurements on hyperfine components of the J = 3 – 2 rotational transition of ¹⁰⁷ Ag ⁷⁹ Br and ¹⁰⁹ Ag⁷⁹ Br at 11.5 GHz were carried out. The electric dipole moment derived for AgBr in its ground electronic and vibrational state is |μ_o| = 5.620 ± 0.030 D.     

The t-butyl group as sensor group of the ortho effect

The ¹³C chemical shift difference between the Me group C atoms and the quaternary C atom of the t-Bu group in 58 p-, m- and o-substituted t-butyl-benzenes has been measured and analysed in terms of inductive. mesomeric and proximity effects. It is shown that the ortho effect is too complex to justify a unified explanation by a correlation treatment.     

Hyperfine structure in the configurations 4f 13 6s6p and 4f 125d6s 2 of TmI

The laser-atomic-beam spectroscopy has been used to make precise measurements of the hyperfine structure in transitions starting from metastable states of the configuration 4f ¹²5d6s ² in¹⁶⁹TmI. With the resulting experimental magnetic dipole hyperfine constantsA _J andA _J values from former investigations a parametric analysis of the hyperfine structure in the configurations 4f ¹³6s6p and 4f ¹²5d6s ² has been performed using wavefunctions from fine structure calculations. A comparison of theoretical and experimental hyperfine constants allowed a test of the reliability of the wave-functions used. The hyperfine parameters respectively hyperfine radial integrals determined from the analysis were compared with corresponding data from ab initio calculations for the ground configuration in TmI.     

Stable organomercury compounds containing an o-iminosemiquinone radical ligand

A series of stable paramagnetic organomercury compounds containing the 4,6-di-tert-butyl-N-(2,6-diisopropylphenyl)-o-iminobenzosemiquinone ligand (imSQ) with the general formula imSQHgR (R = Ph, Et, Prⁿ, Buⁿ, Prⁱ, Hex^c, CH₂SiMe₃, p-FPh, Fc, p-Me₂NPh) were synthesized. The molecular and electronic structures of the synthesized compounds were investigated by EPR spectroscopy and X-ray diffraction. The o-iminosemiquinone ligand shows the unusual amidophenoxy-type coordination mode. In the EPR spectra of the compounds imSQHgR, the hyperfine coupling constant of magnetic mercury isotopes (^199,201Hg) depends on the nature of the substituent R, the temperature, and the nature of the solvent. Voltammetric investigations showed that the complex imSQHgFc undergoes three reversible one-electron redox steps related to the redox transformations of both the o-iminoquinone ligand and the metallocene moiety of the molecule.     

The hyperfine structure in the configuration 4f 135d6s6p in ytterbium

Using Doppler-reduced laser induced fluorescence spectroscopy in an atomic beam, the hyperfine structure of 22 levels of the configuration 4f ¹³5d6s6p in neutral ytterbium has been investigated for the two odd isotopes ¹⁷¹ Yb and ¹⁷¹ Yb. The experimental results have been used in a study of the hyperfine structure in regard to a determination of the one-electron parameters for the magnetic dipole and the electric quadrupole hyperfine coupling of the isotope ¹⁷³ Yb in part II of this work.     

2-Nitromethyl-2-trichloromethyl-1,3-benzodioxoles and 2-nitromethyl-2-trichloromethyl-1,3-benzoxazolines: Synthesis and structure

A reaction of 1-bromo-3,3,3-trichloro-1-nitropropene with pyrocatechol, o-aminophenol, and their substituted derivatives led to 2-nitromethyl-2-trichloromethyl-1,3-benzodioxoles and 2-nitromethyl-2-trichloromethyl-1,3-benzoxazolines. The structure of the compounds synthesized was established by IR, ¹H and ¹³C NMR spectroscopy with HMQC and HMBC ¹H—¹³C experiments, and X-ray diffraction analysis.     

The reaction of aqua-(ethylenediaminetetra-acetato)ruthenium(III) with o-phenylenediamine under aerobic conditions

An electron-transfer reaction between [Ru(III)(Hedta)(H₂O)] and o-phenylenediamine in the presence of O₂ takes place to give a Ru(II)-edta complex with coordinated (bidentate) o-benzoquinone diimine. The complex obtained has been characterized by analysis, magnetic measurements, electronic, IR, ¹H and ¹³C NMR spectral data.     

ESR study of the radical (C6D5)313C produced in a single crystal matrix

The (C₆D₅)₃¹³C radical is produced by the x-irradiation of a single crystal of (C₆D₅)₃¹³C-H. The principal values of the hyperfine coupling with the ¹³C in the methyl position are determined as T₁ = 168 MHz, T₂ = 24 MHz, T₃= 19 MHz. The corresponding spin density is compared with the values obtained in solution by earlier authors. The principal directions are consistent with crystalline structure and show that only one of the two molecules forming the asymmetric unit is broken during irradiation.     

Hyperfine shifts of the 13C-NMR. in low spin iron(3) porphyrin complexes

The ¹³C-NMR. in Zn(II)(Porphin), Fe(III)(Porphin)(CN₂), Zn(II)(Tetraphenyl-porphin), and Fe(III)(Tetraphenylporphin)(CN₂) have been identified, and the ¹³C hyperfine shifts in the iron complexes evaluated. It was found that dipole-dipole coupling with the electron spin localized in the π-orbitals of the aromatic carbon atoms makes an important contribution, to the ¹³C hyperfine shifts. In a preliminary analysis the experimental spin density distribution obtained from the combined ¹H- and ¹³C-NMR.-data is compared with theoretical models of the iron porphyrin complexes.     

Factors affecting stability and equilibria of free radicals—IX: Non-equivalence of aryl groups in 1,1-diaryl-2-benzenesulphonyl-hydrazyls and related compounds

1,1-Bis-(3',5'-di-t-butylphenyl)-2-benzenesulphonyl-hydrazine 11 and the corresponding 2-picryl-hydrazine 13 were synthesized. Oxidation of 11 afforded the stable hydrazyl 12 whose ESR spectrum could be simulated in terms of three hyperfine coupling constants. These experimental data leave no alternative but to assign larger proton hyperfine coupling constants to one aryl group in 12 than to the other. This non-equivalence was interpreted in terms of the Linnett theory. The picrylhydrazyl 14 does not give completely resolved ESR spectra. Structures were ascertained by IR, UV-vis, ¹H NMR and ¹³C NMR spectra.     

Carbon-13 NMR studies of some paramagnetic transition-metal acetylacetonates some linewidth considerations

Carbon 13 isotropic shifts and linewidths have been measured for a series of paramagnetic transition-metal acetylacetonates. The results have been compared with the corresponding NMR parameters of the contiguous protons. The relaxation pathway of the ¹³C spins is controlled by hyperfine interactions with the unpaired electron spins and, in cases where the proton linewidth is also dominated by the hyperfine mechanism, good agreement is obtained between the experimental ¹³C/¹H linewidth ratio and that calculated on the basis of the contact shifts. Pseudocontact interactions can be important in determining the total isotropic shift for both the ¹³C and ¹H nuclei and contrary to previous studies, it is suggested that such effects are also important for V(III) and Mn(III) acetylacetonate.     

Reaction of 2-chlorophenylacetylene with 2,2,2-trichloro-1,3,2λ5-benzodioxaphosphole

According to the ¹³C and ¹H NMR data (one-and two-dimensional spectra), o-chlorophenylacetylene reacts with 2,2,2-trichloro-1,3,2λ⁵-benzodioxaphosphole under mild conditions to give a mixture of diastereoisomeric 2,6-dichloro-4-(2-chlorophenyl)-1,2λ⁵-benzoxaphosphinin-2-ones differing in the configuration of the phosphorus atom and rotation of the o-chlorophenyl group about the C⁴-C_arom bond. Hydrolysis of that mixture leads to 6-chloro-4-(2-chlorophenyl)-2-hydroxy-1,2λ⁵-benzoxaphosphinin-2-one as a single stereoisomer.     

The synthesis and characterization of telluranthrene

The reaction between o-phenylenemercury and finely powdered tellurium metal at temperatures not exceeding 250°C yields a pale yellow crystalline solid. Characterization of this solid by elemental analysis, determination of the molecular mass, mass spectral analysis, and ¹³C and ¹²⁵Te NMR spectral analysis indicates that it is the hitherto uncharacterized telluranthrene.     

Synthesis and spectral characterization of some complexes of platinum(II) containing η-methyleugenol

Several complexes of the formula trans-[Pt(Meug)(Am)Cl₂], Meug: methyleugenol (4-allyl-1,2-dimethoxybenzene), a η²-coordinated olefin, and Am: ammine, methylamine, diethylamine, o-toluidine, m-toluidine, p-toluidine, o-anisidine, m-anisidine and p-anisidine have been prepared. UV, IR, Raman, ¹H NMR, ¹³C NMR and 2D NMR spectra of the complexes were recorded and analyzed.     

ESR- und ENDOR-untersuchungen paramagnetischer zinnkomplexe und strukturanalyse von 3,5-di-t-butyl-1,2-phenylendioxi-bis(o-trifluormethyl-phenyl)-(methanol)zinn(IV)

Triorganyltin compounds react with catechols in organic solvents in the presence of atmospheric oxygen to give at first paramagnetic complexes. The ESR and ENDOR spectra show ¹H, ¹⁹F, ¹¹⁷Sn and ¹¹⁹Sn splittings. The hyperfine structures observed prove that the triorganyltin cations are chelated by o-benzosemiquinone. As the final product of these reactions, diamagnetic compounds can be isolated. As an example, the structure of 3,5-di-t-butyl-1,2-phenylenedioxy-bis(o-trifluoromethyl-phenyl)methanol-tin(IV) was determined by X-ray crystallography. The monomeric compound crystallizes in the space group P$\text{1}$ with a 10.451, b 11.905, c 15.379 Å, α 96.42, β 104.17, γ 111.43° and Z = 2. The penta-coordinated tin atom is 0.5 Å above the phenylenedioxy plane, which occupies one equatorial and one axial coordination site. The second axial position is occupied by the solvent methanol.     

Paramagnetische organothallium(III)-verbindungen in lösung : II. Esr-untersuchungen paramagnetischer diphenylthallium(III)-komplexemit o-aminophenolen und o-phenylendiaminen

Diphenylthalliumhydroxide reacts in organic solvents with o-aminophenols and o-phenylenediamines to form paramagnetic species, the ESR spectra of which have been investigated. The reaction has been run using 32 ligands in numerous solvents, therefore the general application of the reaction is proved.The ESR spectra of the solutions show typical hydrogen nitrogen hyperfine structures indicating a NH-analogue semiquinone structure for the ligands. Furthermore a very large splitting due to magnetic coupling of the free electron with ²⁰³Tl- and ²⁰⁵Tl-nuclei is observed. In contrast to the paramagnetic diphenylthallium—semiquinone complexes [1a], the different coupling of ²⁰³Tl- and ²⁰⁵Tl-nuclei could be resolved in several cases.The thallium splitting observed increases from the semiquinone complexes (~10 G) to the aminophenol radicals (~40 G) and reaches a maximum value for the o-phenylenediamine derivatives (~90 G). The corresponding g-values decrease strongly in this direction. Thus a clear distinction of these classes of ligands becomes possible.The experimental thallium coupling constants and the g-factors depend largely on the substituent of the ligand, the solvent and the temperature. These effects are interpreted in terms of solvation phenomena.Based on the sum of the observed effects we assume that in all cases the radicals investigated are ion pairs in which the diphenylthallium cation interacts with a new type of ligand, namely NH-analogue semiquinones.