13C-NMR. Spectra of Pteridines

¹³C-NMR. spectra of pterin, xanthopterin, isoxanthopterin, leucopterin, lumazine and of the model compounds isocytosine and desamino-isocytosine have been measured as anions and cations in 1 M NaOD, CF₃COOH, H₂SO₄ and FSO₃H solutions. The spectra were analysed by means of heteronuclear double resonance, with the aid of non-decoupled spectra, and by spectral comparison. The results are interpreted in terms of the ionisation state of the pteridines in the four solvents and are compared with those obtained from ¹H-NMR. spectroscopy.     

Second excited singlet state emission spectroscopy of thiocarbonyls. II. Thiocarbonyl chlorofluoride

Single vibronic level emission spectra have been measured for four excitation wavelengths pumping the second excited singlet state of CIFCS. Only resonance fluorescence is observed. Progressions involving Δv″₁ = 0, 1, 2, …, Δv″₆ = 0, 2, 4 … dominate. Analysis of the spectra indicates that neither intra- or intermolecular processes lead to odd Δv′₆ changes and that collisions in the pure gas lead to electronic quenching of molecules in the excited state.     

The physical properties of linear chain systems. I. The optical spectra of [(CH3)4N]NiCl3, Cs(Mg,Ni)Cl3, CsNiCl3, RbNiCl3 and CsNiBr3

The single crystal spectra of pure CsNiCl₃, CsNiBr₃, RbNiCl₃, and [(CH₃)₄]NiCl₃, and the single crystal spectrum of CsNiCl₃ diluted in CsMgCl₃ have been measured to 5°K. The spectra of the magnetically concentrated materials show a number of anomalously intense maxima. These are interpreted in terms of cooperative interactions.     

129Xe-Kernresonanzuntersuchungen von Xenonverbindungen. I. Einfache Xenonderivate

¹²⁹Xenon-NMR Spectra of Xenon Compounds. I. Simple Xenon Derivatives The ¹²⁹Xe-NNR Spectra of simple Xenon compounds have been measured. The analytical value of this method is described. The spectra of Xe, XeF₂, XeF₄, XeOF₄, and XeO₃ are in agreement with the known structures, while XeF₃ is found as Xe₄F₂₄ in inert solution at low temperatures. This had been described recently.     

Protonenresonanzspektren von Pteridinen V. 2-Amino-4-oxo-3,4-dihydropteridine

The proton magnetic resonance spectra of 20 pteridines, i.e. 2-amino-4-oxo-3,4-dihydropteridine and 19 derivatives, have been measured at 100 Mc/s and 60 Mc/s in CF₃COOH under standardized conditions as the mono-cations. The chemical shifts of the vinyl-, methyl- and NH₂-protons are tabulated, and some typical spectra are illustrated. The influence of the substrate concentration and of solvent effects upon the NH-signals have been studied. Protonation always takes place at N(1) or N(3), and an attempt is made to correlate δ(NH₂) and pK_a values.     

Protonization of purine, adenine, and guanine. NMR spectra and structure of mono, di, and tri cations

Proton NMR. spectra of purine, adenine, guanine and methylsubstituted guanines have been measured in CF₃COOH, FSO₃H and FSO₃H? SbF₅? SO₂ at 27° and low temperatures. These conditions permit to study multiple protonation of purines, using chemical shifts of CH, NH and OH protons. The spectra of mono-, di- and tri-cations are described and fully assigned.     

Einkristall-Raman-Spektren von Alaunen. II. [1]. Raman-aktive Gitterschwingungen und FIR-Spektren

Single-Crystal Raman Spectra of Alums. II. Raman-active Lattice Vibrations and F.I.R. Spectra FIR and single crystal Raman spectra of seven different alums have been measured. All observed peaks are assigned to the symmetry species of the factor group T_h. A part of the lattice modes could be assigned to translational and rotational motions of the sulfate (selenate) sublattice and to motions of the crystal water – [Me^I(H₂O)₆]⁺ and [Me^III(H₂O)₆]³⁺ respectively. Comparison of spectra taken at 295 K and 80 K shows no frequency shifts significant for phase transition but a remarkable sharpening of especially those bands which are connected with water motions.     

Luminescence of lead chloride and lead bromide single crystals: I. The excitation and emission spectra

The luminescence of very pure PbCl₂ and PbBr₂ single crystals has been studied at liquid nitrogen and liquid helium temperature. At 10 K, PbCl₂, as well as PbBr₂, exhibits three emission bands in the spectral region investigated, viz., one in the ultraviolet part of the spectrum, a second one in the blue and a third one in the red. In addition, PbCl₂ shows a violet emission at 5 K. If, at 80 K, PbCl₂ and PbBr₂ crystals were exposed to ultraviolet radiation for one hour or more, a yellow emission appeared.Thin film absorption spectra of both lead halides are discussed. The band in the low energy region of the absorption spectra is attributed to the creation of a cation exciton.The excitation spectra of the different emissions have been measured. The thin film absorption spectra and the luminescence excitation spectra are strongly correlated. All emissions are preferentially excited in the low energy region of the absorption spectrum, i.e., the region of the cation exciton absorption band. The ultraviolet emission of both lead halides is discussed and attributed to the recombination of cation excitons.     

The phosphorescence of Fe ions in oxide host lattices. Zero-phonon transitions in Fe/LiAl5O8

Phosphorescence and excitation spectra have been measured of Fe³⁺-doped LiAl₅O₈, β-NaAlO₂, Na-silicate glass and crystalline alumino-silicates. All excitation spectra fit quite well the Tanabe-Sugano diagram for a high spin d⁵ configuration. The expected tetrahedral site symmetry of Fe³⁺ in the host lattices and the value of the crystalline field parameter are strong evidence for phosphorescence of Fe³⁺ ions in tetrahedral oxygen coordination.     

Untersuchungen an Alkylmetallalkoxiden der Elemente Aluminium,Gallium und Indium. I. Die Schwingungsspektren von Dimethylaluminiummethoxid und Methylmethoxialuminiumchlorid

Studies on Alkyl Metal Alkoxides of Aluminium, Gallium, and Indium. I. The Vibrational Spectra of Dimethylaluminiummethoxide and Methylmethoxyaluminiumchloride. The vibrational spectra (IR and RAMAN ) of dimethylaluminium methoxide and deuteromethoxide have been measured and assigned. These trimeric alkoxides consist of puckered six-membered AL₃O₃ ring skeletons probably of C₃ or C₂ symmetry. The structure of methylmethoxyaluminiumchloride could not be determined definitely from the spectroscopic data.     

Microwave spectra of deuterated furans. Revised molecular structure of furan

The microwave spectra of furan, [2-D], [3-D] and [2,5-D₂] furans have been reinvestigated. Also the spectrum of [D₄]furan was assigned and measured. Determination of atomic coordinates by mono- and disubstitution is discussed. The complete substitution structure has been redetermined confirming results of earlier work.     

Beziehungen zwischen Lumineszenzspektrum und Struktur von Seltenerdkomplexen. III. Zur Existenz unterschiedlicher Polyedertypen bei Alkalitetrakis(dibenzoylmethanato)europat(III)-Komplexen

The luminescence spectra of alkali tetrakis(dibenzoylmethido)europate(III) complexes in the crystalline state at 77°K have been measured in the spectral region 510–640 nm. The spectra show the existence of different modifications of these compounds. The spectra of the β-forms are consistent with a site symmetry D₂ at the Eu(III) ion, the spectra of the corresponding α-forms with a site symmetry D₄. A conversion from the β-form into the α-form on heating is observed in some cases. The conversion involves a change from dodecahedral into antiprismatic coordination around the Eu(III) ion.     

Electronic spectra and electrochemistry of disubstituted 2,2′-bipyridinetetracarbonylmolybdenum complexes. Solvent and substituent effects

Electronic absorption spectra of cis-[Mo(CO)₄(n,n′-X₂-bipy)] (n = 4, X = NMe₂, NH₂, OMe, CMe₃, Me, H, Ph, CH:CHPh, CO₂H, Cl, CO₂Me, NO; n=5, X = Me, CO₂H) have been measured at ambient temperature in a variety of solvents of different polarity. Emission spectra from glasses containing the complexes at 77 K have also been measured. The influence of the substituent X on the spectroscopic properties is correlated with the Hammett parameters, σ_p (X) and σ_p⁺ (X). The effect of solvent is correlated with the Taft-Kamlet parameter, π^★, indicating charge redistribution along the permanent dipole axis of the complex. The oxidation and reduction potentials in solution are simply related to the electronic effect of the substituent group, X, and are relatively independent of the solvent. The influence of the metal on these properties is not significant.     

Spinelle mit substituierten Nichtmetallteilgittern. VII. Röntgenographische und elektronische Eigenschaften,Mößbauer- und IR-Spektren des Spinellsystems AgCrSn(S1−xSex)4

Spinels with Substituted Nonmetal Sublattices. VII. X-Ray Investigations, Electronic Properties, Mössbauer, and I.R. Spectra of the Spinel System AgCrSn(S_1?xSe_x)₄ Polycrystalline samples of the spinel system AgCrSn(S_1?xSe_x)₄ have been prepared in the range 0 ? x ? 1. The lattice constants linearly increase with x by 50 pm, the chalcogen parameter has the mean value 0.384. The Mössbauer spectra consist of a weakly split doublet, they are in agreement with Sn(IV) and covalent bonding. The substances are n type semiconductors. I.R. spectra have been measured from 50 cm^?1 to 600 cm^?1.     

The low frequency vibrations of the nucleosides: Uridine,cytidine and inosine. Determination of vibrations associated with the ribose ring

The room temperature far i.r. spectra of the nucleoside cytidine and its deuterated analog cytidine- d₃ have been measured from 200 to 100 cm⁻¹. Several spectral features involving hydroxyl deformations have been identified. Between 200 and 400 cm⁻¹ the spectra of the nucleosides cytidine, uridine and inosine have been compared to those of the respective bases cytosine, uracil and hypoxanthine thereby allowing the identification of several bands associated with deformations of the furanose ribose unit. These frequencies are common among the nucleosides investigated and have been compared to calculated frequencies for “ribose” modes in polynucleotides. Upon cooling to 7 K the cytidine and cytidine-d₃ spectra below 200 cm⁻¹ exhibit a remarkable narrowing resembling a “gas-like” spectra, revealing more spectral features than expected from a group theoretical analysis of the unit cell. The low temperature spectra also exhibit an apparent periodicity. Two equally possible explanations are given; one accounts for the observed periodicity via a vibrational exciton-like theory, while the alternative explanation treats the periodicity as accidental.     

Über Chalkogenolate. 94. Untersuchungen über Trithioallophansäure 3. Ester der Trithioallophansäure [1]

On Chalcogenolates. 94. Studies on Trithioallophanic Acid. 3. Esters of Trithioallophanic Acid. The esters of trithioallophanic acid H₂N? CS? NH? CS(SR) with R = CH₃, CH₂C₆H₅ have been characterized by means of electron absorption spectra, infrared spectra, ¹H NMR spectra, and mass spectra.     

Raman and i.r. spectra of tetramethylcyclobutanedione and the fully deuterated derivative

Raman spectra of tetramethylcyclobutane-1,3-dione (TMCBD) as a polycrystalline solid and in solution in benzene and carbon tetrachloride have been recorded. Infrared and Raman spectra of the fully deuterated molecule have also been recorded. The spectra are consistent with predictions based on a centrosymmetric molecule with a planar cyclobutadione ring and point group D_2h. A fairly complete assignment of the observed spectra is presented for both molecules. A correlation of the frequencies of the fundamentals of TMCBD-h₁₂ and - d₁₂ has been made. Ground state frequencies of fundamentals involved in progressions in the n-π* electronic spectrum have been located.     

UV angle-resolved photoelectron spectra of mixed methylene dihalides using synchrotron radiation

Photoelectron spectra for the dihalomethanes CH₂BrCl, CH₂ClI and CH₂Br₂ have been recorded with photons in the energy range 19–115 eV using Daresbury Laboratory Synchroton Radiation Source. Ionization energies have been measured for all valence falling within this energy including Br 3d and I 4d orbitals. Asymmetry parameters have been measured for all intense ionization processes and characteristic Cooper minima observed for halogen lone pair orbitals. For CH₂ClI lone pair orbital β spectra show strong evidence of mixed halogen character although a similar situation is not observed for CH₂BrCl. Partial photoionization cross sections are tabulated for the observed ionization processes. Detailed spectra are presented for the molecule CH₂ClI since this appears to be the first photoelectron study of this molecule.     

Carbon-13 NMR spectra of retinal1 and its related compounds

Carbon-13 NMR spectra of all-trans retinal₁ and vitamin A₁ were measured by the pulse Fourier transform method in CCl₄. All peaks in these spectra were assigned from considerations of chemical shifts, half proton-decoupled spectra, spin-lattice relaxation times and induced chemical shift by the addition of shift reagent. The carbon-13 NMR spectrum was also measured for all-trans retinal₁ which had been exposed to the sunlight for three hours, and the induced isomer was proposed to be 11-s-cis retinal₁.     

1H and 13C n.m.r. spectra of dichloro(trans-2-chlorovinyl)arsine

Proton and carbon magnetic resonance spectra of Lewisite or dichloro(trans-2-chlorovinyl)arsine have been measured and the results are compared with the n.m.r. spectral parameters of other trans-1,2-substituted ethylenes. The coupling constants can be rationalized by substituent electronegativity. The chemical shifts show an unusually large paramagnetic effect from the AsCl₂ group.