The wavenumber values in the carbonyl and NH2 stretching regions of a further 21 amides, all ortho substituted benzamides or heterocyclic carboxamides, are presented. The previous limits on the spectral ranges are thereby widened marginally, but in predictable ways. The NH stretching vibrations of ortho alkoxybenzamides are related to benzamide itself by a curve dependent on intramolecular hydrogen bonding, quantified by further elaboration of the Linnett equations to account for non-equivalence of the two NH bonds. Deuteration experiments enabled uncoupling of the NH bonds and assignment of bond strengths. Although it is widely believed that there is no coupling between XH and XD stretching frequencies, we show that the true NH frequency is raised by 2cm-1 as a result of deuterium coupling in NHD groups. The calculation of ND2 wavenumbers from those of the fundamental and first overtone of the NH2 values was carried out by 4 procedures. Better concordance with the antisymmetric vibration than the symmetric vibration was observed. The calculated shortening of the NH bonds on deuteration is 0.0035±0.0009Å.

The nature of the elusive muonium centre in sulphur is re-examined in the light of new data on its level-crossing resonance and spin–lattice relaxation. The aim is to provide a model for the solid-state chemistry of interstitial hydrogen in this element, which is as yet unknown, as well as to solve one of the longest standing puzzles in μSR spectroscopy, namely the surprisingly strong depolarization of muons mimicking ion-implanted protons in this innocuous non-magnetic material. The paramagnetic muonium (and by inference hydrogen) centre is confirmed to have the character of a molecular radical, but with huge anisotropy at cryogenic temperatures and a striking shift of the resonance at ordinary temperatures, the hyperfine parameters appearing to collapse and vanish towards the melting point. New density-functional supercell calculations identify a number of possible structures for the defect centre, including a novel form of bond-centred muonium in a closed-ring S8Mu complex. Simulations of the spin dynamics and fits to the spectra suggest a dynamical equilibrium or chemical exchange between several configurations, with occupancy of the bond-centre site falling from unity at low cryogenic temperatures to zero near the melting point.

Solution and single-crystal FT-Raman spectroscopy with polarization analysis have been used to assign a frequency of 147 cm−1 to the totally symmetric Cr3O stretching vibration of the complex cation in the dark coloured compound [Cr3O(OOCCH3)6(H2O)3]Cl ·5H2O. For this vibration, the polarizability derivatives parallel to the metal triangle are shown to be greater in magnitude than that perpendicular to the triangle.

The iron(II) nitrosyl complexes [FeL(NO)] (L = ethylenediamine-, ethylenedioxydiethylenedinitrilo- or 1,6-diaminohexane-N,N,N',N'-tetraacetate) have been studied by absorption, low-temperature magnetic circular dichroism (MCD) and EPR spectroscopies. All three complexes exhibit similar spectral properties. The EPR spectra can be understood in terms of an axial site with a S = 3/2 electronic ground state. Analysis of the optical spectra has been carried out following extended-Huckel molecular orbital calculations on [Fe(H2O)5(NO)]2+ assuming C4v symmetry for the iron(II) ion with the Fe-NO bond providing the major axis of distortion. Thus it has been possible to identity and assign the MCD transitions within the Fe-NO fragment of the complexes. This analysis provides a basis for understanding and interpreting the magneto-optical spectra of the nitrosyl complexes of iron(II) sites in non-haem iron proteins.

The infrared spectra of the dimethyl complexes of zinc, cadmium and mercury, isolated in argon matrices, have been measured. Earlier assignments of the spectrum of the zinc compound appear to have included a band due to a methane impurity. A study of the RAIR spectrum of a thin film of ZnMe2 on a copper surface has revealed that the molecules in the film are strongly orientated and the additional information thus obtained has made it possible to suggest some reassignment of the spectra of all three compounds.

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTQuantitative magnetic circular dichroism spectroscopyRobin G. Graham and Roger. GrinterCite this: J. Phys. Chem. 1990, 94, 16, 6282–6285Publication Date (Print):August 1, 1990Publication History Published online1 May 2002Published inissue 1 August 1990https://pubs.acs.org/doi/10.1021/j100379a025https://doi.org/10.1021/j100379a025research-articleACS PublicationsRequest reuse permissionsArticle Views123Altmetric-Citations-LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InRedditEmail Other access options Get e-Alerts

Absorption and magnetic circular dichroism (MCD) spectra of iron atoms isolated in xenon matrices have been measured and their magnetization properties studied. The high signal intensity and optical quality of the matrices has allowed the assignment of many more transitions than hitherto. The magnetization measurements reveal considerable guest host interaction, though there is little evidence of this in the spectra. Detailed analysis of the magnetization data shows that they can be interpreted quite well in terms of an essentially axial crystal field splitting of the 5 D4 ground state which places the two ‖MJ‖=4 levels about 100 cm−1 below the ‖MJ‖=3. By extending the theoretical treatment to include a small mixing of the two ‖MJ‖=4 levels it is possible to improve the fit of the higher temperature data. These results demonstrate the value of MCD measurements, particularly where a system is electron paramagnetic resonance (EPR) silent.

The electronic and magnetic circular dichroism (MCD) spectra of scandium atoms isolated in argon, krypton and xenon matrices have been measured and the bands assigned. Some aspects of the assignment present problems and the resulting matrix shifts are rather irregular. Magnetization studies of the above systems are also reported and the data show that there are particularly strong guest—host interactions in the case of Sc/Xe. Furthermore, they suggest that there is significant guest—host interaction in the ground electronic state. Computer simulation of the magnetization curves and the MCD spectra, using a crystal field model, enables some tentative suggestions concerning the nature of the matrix sites to be made. All sites show an axial character. MCD bands of a scandium dimer have been observed. The form and magnetization properties of one band support a 5Σ ground state for the molecule.

The electronic absorption spectra and magnetic circular dichroism (MCD) spectra of matrix-isolated aluminium atoms have been studied with particular reference to the 3p4s and 3p3d transitions. The g values of the isolated atoms also have been measured via the MCD magnetization technique. It is found that, in all matrices, the orbital angular momentum of the atom is heavily quenched giving g values very near 2.0. A consistent analysis of this phenomenon and of the spectra has been developed using a model in which the surrounding noble gas atoms exert an electrostatic field upon the aluminium atom and also enter into molecular orbital formation with it. This interpretation leads to the conclusion that the spin-orbit coupling of the optical electron is negative in both ground and excited states for Al/Kr and Al/Xe, but in the excited state only for Al/Ar. These results confirm and extend the findings of earlier EPR measurements.

The absorption and MCD spectra of gallium atoms isolated in argon, krypton and xenon matrices have been measured. The ground-state magnetic properties of the isolated atoms have also been investigated by means of the MCD magnetization technique. The data show evidence for the occupation of several sites and the MCD spectra, in particular, show some remarkable changes on annealing. Unfortunately, it has not proved possible to make a correlation between band position, matrix shift and trapping site with the result that considerable uncertainty remains concerning the assignment of the spectra and the interpretation of the shifts. The magnetization experiments reveal that some isolated atoms have largely quenched orbital angular momentum, which others approximate closely to the g = 23 of the gas phase atom. The g values determined by fitting the magnetization curves are found to be in quite good agreement with the EPR results of Ammeter and Schlosnagle. However, it should be noted that the fitted magnetization curves, and hence the g values determined, depend upon the details of the model for the ground state. The magnetization properties are discussed in terms of the geometries of the sites occupied.

Magnetic circular dichroism has been used for the first time to study the magnetisation properties of some matrix-isolated species. The samples chosen for measurement have one, three, five and six unpaired electrons in their ground electronic states and, nominally, no orbital angular momentum. The experimental results follow the theoretical predictions very closely, but the nature of the magnetisation function is such that it is not easy to distinguish between different combinations of g-value and total spin angular momentum.

A Slater-Condon calculation including a crystal field perturbation has been performed for Pd atoms. The optical spectrum of Pd in Ne is reproduced very well with this calculation, assuming a repulsive crystal field of Oh symmetry.

The gas- and matrix-phase electronic spectra of the silver dimer in the energy region below 5.5 eV have been assigned. It is found that a satisfactory interpretation of these spectra, particularly that in the matrix, can only be obtained if the mixing of Σ and Π states by second-order spin—orbit coupling is explicitly included in the analysis. Electron repulsion effects are found to play an important, but less obvious, role.

Matrices for the Euler-angle rotations of real, cartesian p, d and f atomic orbitals have been calculated. The results are presented in terms of a small number of primary matrix elements, together with rules by means of which the remaining elements may be readily derived from those given.

Matrix absorption and magnetic circular dichroism studies on Os16O4 and Os18O4 have been carried out to clarify the number of electronic transitions present in the region. The spectra show that the irregular vibrational structure in the 16O species with its onset at ∼276 nm is perfectly regular in the 18O compound. The system is, therefore, interpreted as a single electronic system analogous to that observed in the permanganate ion. The Raman spectrum of Os16O4 single crystal has also been obtained.

The electronic absorption spectra of copper atoms isolated in argon, krypton, and xenon matrices have been measured in the range 3.6–8.6 eV using a synchrotron radiation source. By correlating the results with gas-phase data, and with the help of magnetic circular dichroism measurements and calculations of energies and intensities, a detailed assignment of the 3d→4p region of the spectra has been proposed. A band at 6.357 eV in the xenon matrix is assigned to the Rydberg 4s→5p transition with a fair degree of confidence, and two high-energy bands in the krypton matrix are tentatively assigned to Rydberg 3d→5p transitions. The matrix shifts confirm the view that the principal influence of the matrix is upon the upper orbital involved in the transition. Attention is drawn to the fact that matrix perturbations may increase the number of observable spectral bands, either by lifting degeneracies or by mixing allowed character into previously forbidden transitions.

Chemischer InformationsdienstVolume 14, Issue 43 Physical Inorganic Chemistry ChemInform Abstract: ELECTRONIC AND MAGNETIC CIRCULAR DICHROISM SPECTRA OF MATRIX-ISOLATED NICKEL ATOMS R. GRINTER, R. GRINTERSearch for more papers by this authorD. R. STERN, D. R. STERNSearch for more papers by this author R. GRINTER, R. GRINTERSearch for more papers by this authorD. R. STERN, D. R. STERNSearch for more papers by this author First published: October 25, 1983 https://doi.org/10.1002/chin.198343004Read the full textAboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinked InRedditWechat No abstract is available for this article. Volume14, Issue43October 25, 1983 RelatedInformation