Co-acquisition of hyperpolarised 13C and 15N NMR spectra

Recent developments in dynamic nuclear polarisation now allow significant enhancements to be generated in the cryo solid state and transferred to the liquid state for detection at high resolution. We demonstrate that the Ardenkjaer-Larsen method can be extended by taking advantage of the properties of the trityl radicals used. It is possible to hyperpolarise 13C and 15N simultaneously in the solid state, and to maintain these hyperpolarisations through rapid dissolution into the liquid state. We demonstrate the almost simultaneous measurement of hyperpolarised 13C and hyperpolarised 15N NMR spectra. The prospects for further improvement of the method using contemporary technology are also discussed.     

1H, 13C and 15N NMR spectra of ciprofloxacin

1H NMR assignment, including the values of delta(H) and J(H,H) for the cyclopropane moiety, and 13C NMR and 15N NMR spectral data for ciprofloxacin are presented.     

13C, 15N and 29Si NMR spectra of triazasilatranes

¹³C, ¹⁵N and ²⁹Si chemical shifts and ²⁹Si¹H, ²⁹Si¹³C and ²⁹Si¹⁵N coupling constants as well as SiH bond stretching frequencies in the triazasilatranes (I) (2,5,8,9-tetraaza-1-silatricyclo[3.3.3.0^1,5] undecanes) and model compounds, tris(alkylamino)silanes with R_Si = H, Me, CH₂CH (Vi) and C₆H₅ (Ph) were measured. A stronger intramolecular N → Si bonding was revealed in I compared with their oxygen analogues, silatranes (II). This was assumed to be caused by the higher polarity of the equatorial SiX bonds in I (X = NH) in comparison with II (X = O).     

13C and 15N NMR spectra of 4-substituted-1-dimethylphosphonopiperazines

¹³C and ¹⁵N NMR chemical shifts and ¹³C-³¹P and ¹⁵N-³¹P coupling contants are reported for a series of ten 4-substituted-1-dimethylphosphonopiperazines.     

13C and 15N NMR spectra of 2,3-substituted 2H-azirines

The ¹³C and ¹⁵N NMR spectra of a series of 2,3-substituted 2H-azirines have been studied. The ¹⁵N chemical shift for the nitrogen in the azirine ring is found at much higher field than in acyclic imines with a considerable electronic effect for the substituents on the double bond. Cooperative steric and electronic effects associated with substituents on the unsaturated carbon atom of the ring were found to influence the shielding of the ¹³C and ¹⁵N nuclei. Reaction constants have been calculated for 2-alkyl(aryl)-3-phenylazirines. It has been shown that the azirine ring has a powerful —I effect (when compared with the phenyl ring) that exceeds the analogous value for the cyano group.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 9, pp. 1181–1183, September, 1986.     

13C NMR spectra and structure of hydroxy- and amino-substituted azo derivatives of benzene and naphthalene

Conclusions It was shown by the¹³C NMR method that the hydroxy- and amino-substituted azo derivatives of benzene and naphthalene have an azo structure under the studied conditions.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 5, pp. 1185–1188, May, 1984.The authors are grateful to N. V. Korsakov and L. N. Savos'kin for supplying some of the compounds.     

13C NMR spectra of alkenylsilanes

Conclusions The¹³C NMR spectra of 12 alkenylsilanes were measured and the values of the increments of the chemical shifts of the (CH₃)₃Si group were determined for some allylsilanes.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 4, pp. 938–939, April, 1978.     

13C and 15N NMR spectra of high‐energy polyazidocyanopyridines

¹³C and ¹⁵N NMR spectra of high‐energy 2,4,6‐triazidopyridine‐3,5‐dicarbonitrile, 2,3,5,6‐tetraazidopyridine‐4‐carbonitrile and 3,4,5,6‐tetraazidopyridine‐2‐carbonitrile are reported. The assignment of signals in the spectra was performed on the basis of density functional theory calculations. The molecular geometries were optimized using the M06‐2X functional with the 6‐311+G(d,p) basis set. The magnetic shielding tensors were calculated by the gauge‐independent atomic orbital method with the Tao–Perdew–Staroverov–Scuseria hybrid functional known as TPSSh. In all the calculations, a polarizable continuum model was used to simulate solvent effects. This approach provided accurate predictions of the ¹³C and ¹⁵N chemical shifts for all the three compounds despite complications arising due to non‐coplanar arrangement of the azido groups in the molecules. It was found that the ¹⁵N chemical shifts of the N_α atoms in the azido groups of 2,4,6‐triazidopyridines correlate with the ¹³C chemical shifts of the carbon atoms attached to these azido groups. Copyright © 2016 John Wiley & Sons, Ltd.     

13C NMR spectra of S-methylquinolines

The ¹³C chemical shifts and the increments () of the SCH₃ group in the NMR spectra of S-methylquinolines were measured. It is shown that the chemical shifts of S-methylquinolines correlate satisfactorily with the total charges on the carbon atoms calculated within the CNDO/2 approximation. The coupling of the SCH₃ group with the quinoline ring was examined on the basis of the values.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 12, pp. 1665–1671, December, 1979.The authors thank É. É. Liepin' for his discussion of the results.Original article submitted October 1, 1978.     

Complete assignments of the 1H and 13C NMR spectra of 15 limonoids

Unambiguous and complete assignments of ¹H and ¹³C NMR chemical shifts for 15 limonoids, eight of them found in natural sources and seven other synthetic derivatives, are presented. The assignments are based on 2D shift‐correlated [¹H,¹H‐COSY, ¹H,¹³C‐gHSQC‐¹J(C,H), ¹H,¹³C‐gHMBC‐ⁿJ(C,H) (n = 2 and 3)] and NOE experiments. Copyright © 2003 John Wiley & Sons, Ltd.     

13C NMR spectra of protonated S-methylquinolines

The signals in the¹³C NMR spectra of protonated 2-, 3-, 4-, 5-, 6-, and 8-S-methylquinolines in solution in 6 N DCl were assigned. The changes in the¹³C chemical shifts relative to the neutral molecules were compared with the results of calculations within the CNDO/2 approximation. It is shown that when the molecules are protonated, the shift of the¹³C signals is due to changes in the charges and the paramagnetic components of shielding of the nuclei.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 5, pp. 663–665, May, 1980.     

13C NMR spectra of substituted thiacyclohexanes

Conclusions The use of the¹J_CH values permits making an unequivocal assignment of the¹³C signals in the spectra of substituted thiacyclohexanes. The steric arrangement of the substituants in 2,4-disubstituted thianes can be established on the basis of the chemical shift values of the C⁶ nuclei. The obtained data can be used to identify the cyclic organosulfur compounds that are isolated from crude petroleum.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 2, pp. 452–454, February, 1982.     

13C NMR spectra of adamantane derivatives

The carbon-13 chemical shifts of mono- and 1,3-disubstituted adamantanes are reported. The effects caused by the substituents are compared with those met in aliphatic and alicyclic compounds. It is shown that the 1,4-interactions have only minor importance in l-substituted adamantanes. The influence of polar groups on the chemical shifts of γ- and δ-carbon atoms is a typical ‘through-the-bonds’ interaction and correlates with inductive parameters of the substituents.     

The 13C NMR spectra of homoisoflavonoids

The study of a set of 3-benzylidene-4-chromanones, 3-benzyl-4-chromanones, 3-benzyl-3-hydroxy-4-chromanones and 3-benzylchromones (homoisoflavonoids) by ¹³C NMR spectroscopy shows the influence of the structure of these molecules on the chemical shifts of the more characteristic carbon atoms at positions 2, 3 and 4.     

13C NMR spectra of polymethoxy- and methylenedioxyflavonols

The ¹³C NMR spectra of 20 polymethoxy- and/or methylenedioxyflavonols are reported. In key cases assignments have been made by examination of fully coupled spectra.     

13C NMR spectra of polycyclic diaziridines

A significant difference between experimental¹³C NMR chemical shifts and those predicted from the¹³C NMR/IR databank was found for bi- and tricyclic diaziridines. Quantum chemical (AMI) and molecular-mechanical (MMX) calculations showed that the relative chemical shift of the nodal C atom is dependent mainly on deformations of the C-C-C valence angle at this atom.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 11, pp. 2496–2499, November, 1991.     

13C NMR spectra of arylnaphthalene lignans

The¹³C NMR spectra have been investigated of a number of arylnaphthalene lignans of plant origin: daurinol and its acetyl derivative and reduction product, justicidin A, justicidin B and its reduction product and the diacetyl derivative of the reduction product, and diphyllin and its acetate. The values of the chemical shifts of the carbon atoms in the spectra of the compounds investigated and the nature of their change according to structural factors are discussed and an assignment is made of the resonance lines in the spectra. The characteristics of the spectrum of one compound are used as models for others. The parameters of the¹³C NMR spectra of a number of naphthalene derivatives are also used. On the basis of the results of the assignment of the signals, difference values of the chemical shifts of the carbon atoms in the series of compounds investigated have been determined. Using the experimental results as a background, some examples taken from the literature of investigations of the¹³C NMR spectra of related compounds have been analyzed.Institute of the Chemistry of Plant Substances, Academy of Sciences of the Uzbek SSR, Tashkent. Translated from Khimiya Prirodnykh Soedinenii, No. 1, pp. 76–90, January–February, 1987.