207Pb N.M.R. of lead(II) soaps in solid,liquid-crystalline and liquid phases

Abstract

²⁰⁷Pb N.M.R. data are reported for a number of even chain length lead(II) carboxylates (soaps) at various temperatures. At room temperature, the solid lead(II) decanoate and tetradecanoate show similar spectra, with a single metal ion site, and modest shielding anisotropy. As the temperature is increased, the soaps (hexanoate to octadecanoate) all form a highly ordered smectic phase, which gives a very broad ²⁰⁷Pb signal of linewidth comparable to that of the solid phase. At higher temperatures, the hexanoate to dodecanoate soaps form a lamellar L _α (smectic A) phase, whilst the longer chain length carboxylates melt directly to the liquid phase. Both the lamellar L _α and liquid phase give fairly sharp, isotropic signals, whose chemical shifts and linewidths are strongly temperature dependent. Possible explanations for this effect include paramagnetic contributions to the shielding tensor from low-lying electronic states of Pb(II), and contributions to the observed signal from different coordination species produced in the lead(II) carboxylate system. Although there are discrete changes in chemical shift at the phase transition, the magnitudes observed in all the phases are similar, suggesting that there are no dramatic changes in the metal coordination environment.     

Multinuclear NMR (1H,13C,15N,17O) studies of intramolecular interactions in 1-vinylpyridones and quinolones

¹H and¹³C NMR was used to estimate the dihedral angles between the planes of the vinyl group and the hetero ring for 1-vinylpyridones and quinolones. The¹H,¹³C,¹⁵N, and¹⁷O NMR data showed the existence of a specific intramolecular weak hydrogen bond between the -H atom of the vinyl group and the O atom in 1-vinyl-2-pyridones and 2-vinyl-1-isoquinolone.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 7, pp. 1539–1547, July, 1990.     

1H and 13C NMR studies of (phenylethynyl) (triphenylphosphine) gold(I)

A ¹H and ¹³C NMR study of (phenylethynyl) (triphenylphosphine) gold(I) is presented. Contrary to the solid state findings, the existence of Au … Au contacts in solution can be excluded on the basis of experimental results. The ¹³C chemical shifts of various Au, Ag and Cu triphenylphosphine complexes and the corresponding SCS values are considered to rationalize the electronic behaviour of the ligand on complexation.     

1H and 13C NMR studies on 1,3,2-dioxarsolanes

The ¹H and ¹³C NMR spectra of a series of 1,3,2-dioxarsolanes have been obtained at 2.1 T and some at 9.4 T. The chemical shifts and spin-spin coupling constants have been obtained from complete spectral analyses of the ¹H and proton-coupled ¹³C spectra. The spectral data are interpreted on the basis of two rapidly interconverting half-chair conformers with a pseudoaxial substituent at arsenic. Unique assignment of syn/anti or cis/trans geometries have been made from ¹H or ¹³C NMR spectroscopy alone. The syn and trans isomers of the 4-methyl- and 4,5-dimethyl-1,3,2-dioxarsolanes, respectively, appear to be conformationally biased towards the forms with pseudoequatorial methyl groups. The general trends in the geminal and vicinal ¹H? ¹H and ¹³C? ¹H coupling constants are interpreted in terms of stereospecific, electronegativity and lone-pair effects of the oxygen heteroatoms and conformational factors. The NMR data on the 1,3,2-dioxarsolanes are discussed with reference to related 1,3-dithoxa- and 1,3-dithia- five-membered rings with As, P, S or C at the 2-position.     

1H and 13C NMR studies of some aromatic dilactones (precursors of paracyclophanes)

Carbon-13 and proton NMR data of macrocyclic diaromatic dilactones are presented. The observed behaviour of the spectra as a function of temperature shows that the energy barrier for the re-orientation of the side chains is lower than 49 kJ mol^?1 (12 kcal mol^?1) and that the energy barrier for the rotation of the aromatic rings is larger than 99 kJ mol^?1 (24 kcal mol^?1). Hence, chiral substituted dilactones of this type will be resolvable, and the enantiomers can be easily handled at room temperature.     

Structure and dynamics of the lincomycin-copper(II) complex in water solution by (1)H and (13)C NMR studies

The copper(II) complex of lincomycin in water solution at pH = 7.15 was characterized by (1)H and (13)C NMR and UV-vis spectroscopy. A 1:1 complex is formed in these conditions. The temperature dependence of spin-lattice relaxation rates was measured, showing that all protons behave in a similar fashion and slow exchange conditions prevail. The spin-lattice relaxation rate enhancements were interpreted by the Solomon-Bloembergen-Morgan theory. Reorientational dynamics of the complex was approximated by evaluating the motional correlation time of free lincomycin in water solution. The observed proton and carbon relaxation rate enhancements allowed us to calculate copper-proton and copper-carbon distances that were used for building a molecular model of the complex. The obtained data provide an interpretation of the relatively high stability constant.     

High-resolution 13C NMR studies of solid 1,4-bis(n-butylamino)anthraquinone

High-resolution ¹³C NMR spectra of solid 1,4-bis(n-butylamino)anthraquinone are presented. In spectra measured at 22.6 MHz the effects of two short-range and two long-range residual (¹³C, ¹⁴N) dipolar couplings have been observed. Only the short-range effects are observable in the 50.3 MHz spectra. These typical asymmetric doublets allow the determination of the ¹⁴N nuclear quadrupole coupling constant (χ=e²Qq/h=?3.0 MHz), the asymmetry parameter (η=0.3) and the orientation of the electric field gradient tensor of the ¹⁴N in the molecular framework.     

1H and 13C NMR studies on N-(cyclohex-2-en-1-ylidene)amines

¹H and ¹³C NMR spectroscopy allow the identification of diastereomeric Z- and E-N-(cyclohex-2-en-l-ylidene)amines and the assignment of their configuration.     

13C and 1H NMR spectral studies of N-alkylmethylquinolinium salts

¹³C and ¹H chemical shifts of fourteen N-alkylmethylquinolinium salts in DMSO-d₆ are reported, and compared with those of the eleven corresponding methylquinoline bases. The influence of ring substitution by methyl groups in the salts and substitution at the nitrogen atom and the effect of the anion are discussed.     

Multinuclear (13C, 15N) NMR study of polyethyleneimine-based polymers

Representative polyethyleneimine-based polymers have been studied by ¹³C- and ¹⁵N-nuclear magnetic resonance spectroscopy and an extensive set of chemical shift assignments has been proposed for the complex spectra obtained. The samples in question represent a complex mixture of both protonated and nonprotonated primary, secondary, and tertiary as well as quaternary monomeric units.     

1H and 13C NMR studies of some germacrones and isogermacrones

The ¹H and ¹³C NMR spectra of the trans,trans-, cis,cis- and cis-C-3–C-4, trans-C-7–C-8-germacrones and of the cis-C-2–C-3, trans-C-7–C–8, trans-C-2–C-3, cis-C-7–C-8- and cis,cis-isogermacrones are analysed. The last two isogermacrones are new compounds. The C-2–C-3 double bond in the previously described isogermacrone is found to be of cis configuration, contrary to the hitherto accepted trans arrangement.     

Computational 1H and 13C NMR in structural and stereochemical studies

Present review outlines the advances and perspectives of computational ¹H and ¹³C NMR applied to the stereochemical studies of inorganic, organic, and bioorganic compounds, involving in particular natural products, carbohydrates, and carbonium ions. The first part of the review briefly outlines theoretical background of the modern computational methods applied to the calculation of chemical shifts and spin–spin coupling constants at the DFT and the non-empirical levels. The second part of the review deals with the achievements of the computational ¹H and ¹³C NMR in the stereochemical investigation of a variety of inorganic, organic, and bioorganic compounds, providing in an abridged form the material partly discussed by the author in a series of parent reviews. Major attention is focused herewith on the publications of the recent years, which were not reviewed elsewhere.     

1H and 13C NMR studies of 2-functionalized 5-(methylsulfonyl)-1-phenyl-1H-indoles

The 1H and 13C NMR resonances of thirty 2-functionalized 5-(methylsulfonyl)-1-phenyl-1H-indoles were assigned completely and unequivocally using the concerted application of one- and two-dimensional experiments (DEPT, gs-HMQC and gs-HMBC). Finally, the influence of the 2-substituent of 5-(methylsufonyl)-1-phenyl-1H-indoles on the carbon atoms of the indole moiety was estimated.     

13C and proton NMR spectra of 2(1H)pyrazinones

¹³C and proton NMR spectra data are given for eleven 2(1H)pyraziones. Assignments of chemical shifts were made by methods which included: deuterium exchange with certain protons of 3-alkyl substituents; change of chemical shifts of certain carbon atoms with change in pH; the use of long-range coupling constants for ¹³C to protons; and various correlations among assigned spectra.     

1H and 13C NMR studies of 7-azaindole and related compounds

The ¹H and ¹³C chemical shifts, proton-proton coupling constants, and one-bond carbon-hydrogen coupling constants have been obtained for 7-azaindole, 1-methyl-7-azaindole, their corresponding methyl iodide salts, and the related compound 7-methyl-7H-pyrrolo [2,3-b]pyridine. are different from those of either 7-azaindole or 1-methyl-7-azaindole.     

(1)H, (13)C NMR and X-ray crystallographic studies of highly polyhalogenated derivatives of costunolide lactone

The costunolide lactone, a sesquiterpene compound isolated from Zaluzania triiloba species, reacted with several dihalocarbene sources produced by trihaloform-NaOH under successive phase transfer reactions yielding mono-, bis- and tris-dihalocyclopropane adducts. The structures, as well as the configurational assignments of the different derivatives, were established by (1)H and (13)C NMR spectroscopy and assisted by X-ray crystallographic and molecular modelling studies. The specific shielding of protons in the neighbourhood of different halogens on the cyclopropane moieties was correlated to the pseudocontact interactions.     

1H NMR studies of nickel(II) complexes of n-hydroxylpropyl-salicylaldimines

The¹H NMR spectra of various monomeric, dimeric and trimeric complexes of Ni(II) with n-hydroxypropyl-salicylaldimines have been measured and assigned. They are consistent with structures previously proposed for these complexes.     

1H and13C NMR study of complexes of nickel(II) with water and saturated alcohols

Journal of Structural Chemistry -     

1H, 13C and 19F NMR studies on fluorinated ethers

The enflurane and ethoxyflurane ¹H, ¹³C and ¹⁹F NMR spectra are examined—including sign determination of FF and FH couplings—and considered in the light of previously reported results for methoxyflurane. Conformational differences between methoxyflurane and the former two molecules are indicated by through space FH coupling constants and by the nonequivalence of geminal fluorine nuclei. Populations of conformers about the CC bond are estimated.     

Investigation of 2,6-diarylthiacyclohexanes and their complexes with Pt(II) and Pd(II) by 1H and 13C NMR spectroscopy

A conclusion regarding a diequatorial orientation of the aryl substituents was drawn on the basis of a study of the ¹H and ¹³C NMR spectra of 2,6-diarylthiacyclohexanes. A trans structure of the complexes with an equatorial Smetal bond was established by a comparative analysis of the ¹³C NMR spectra of 2,6-diarylthiacyclohexanes and their complexes with Pt(II) and Pd(II).Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 5, pp. 609–613, May, 1987.