Comparative analysis of 13C shielding constants stereospecificity in the silicon and germanium derivatives of acetylenic aldehyde and ketone oximes based on the 13C NMR spectroscopy and GIAO calculations

In the acetylenic aldehyde oximes with substituents containing silicon and germanium, the ¹³C NMR signal of the C‐2 carbon of triple bond is shifted by 3.5 ppm to lower frequency and that of the C‐3 carbon is moved by 7 ppm to higher frequency on going from E to Z isomer. A greater low‐frequency effect of 5.5 ppm on the C‐2 carbon signal and a greater high‐frequency effect of 11 ppm on the C‐3 carbon signal are observed in the analogous acetylenic ketone oximes. The carbon chemical shift of the C?N bond is larger by 4 ppm in E isomer relative to Z isomer for the aldehyde and ketone oximes. The ²⁹Si chemical shifts in the silicon containing acetylenic aldehyde and ketone oximes are almost the same for the diverse isomers. The trends in changes of the measured chemical shifts are well reproduced by the gauge‐including atomic orbital (GIAO) calculations of the ¹³C and ²⁹Si shielding constants. Copyright © 2009 John Wiley & Sons, Ltd.     

Pronounced stereospecificity of 1H, 13C, 15N and 77Se shielding constants in the selenophenyl oximes as shown by NMR spectroscopy and GIAO calculations

In the ¹H and ¹³C NMR spectra of 1‐(2‐selenophenyl)‐1‐alkanone oximes, the ¹H, the ¹³C‐3 and ¹³C‐5 signals of the selenophene ring are shifted by 0.1–0.4, 2.5–3.0 and 5.5–6.0 ppm, respectively, to higher frequencies, whereas those of the ¹³C‐1, ¹³C‐2 and ¹³C‐4 carbons are shifted by 4–5, ～11 and ～1.7 ppm to lower frequencies on going from the E to Z isomer. The ¹⁵N chemical shift of the oximic nitrogen is larger by 13–16 ppm in the E isomer relative to the Z isomer. An extraordinarily large difference (above 90 ppm) between the ⁷⁷Se resonance positions is revealed in the studied oxime isomers, the ⁷⁷Se peak being shifted to higher frequencies in the Z isomer. The trends in the changes of the measured chemical shifts are well reproduced by the GIAO calculations of the ¹H, ¹³C, ¹⁵N and ⁷⁷Se shielding constants in the energy‐favorable conformation with the syn orientation of the? C?N? O? H group relative to the selenophene ring. Copyright © 2009 John Wiley & Sons, Ltd.     

Solid state13C NMR spectra of metal carbonyl clusters

The solid state¹³C NMR spectra of four¹³CO enriched carbonyl clusters having a tri-iron metallic core have been analyzed to provide structural and dynamic information. In Fe₃(CO)₁₂ (1), the high temperature spectra suggest the occurrence of large amplitude motions of the CO groups around their position at the vertexes of the coordination polyhedron in addition to the motion involving the Fe₃-triangle previously detected in the VT-¹³C MAS spectra.¹³C and³¹P NMR data of Fe₃(CO)₁₁PPh₃ (2) indicates the presence of one molecule in the asymmetric unit in apparent disagreement with the previously reported X-ray data. Furthermore, we show that structural information can be obtained from the chemical shift tensor components readily available from the analysis of the spinning sideband manifold.     

Stereospecificity of 1H, 13C and 15N shielding constants in the isomers of methylglyoxal bisdimethylhydrazone: problem with configurational assignment based on 1H chemical shifts

In the ¹³C NMR spectra of methylglyoxal bisdimethylhydrazone, the ¹³C‐5 signal is shifted to higher frequencies, while the ¹³C‐6 signal is shifted to lower frequencies on going from the EE to ZE isomer following the trend found previously. Surprisingly, the ¹H‐6 chemical shift and ¹J(C‐6,H‐6) coupling constant are noticeably larger in the ZE isomer than in the EE isomer, although the configuration around the –CH═N– bond does not change. This paradox can be rationalized by the C–H?N intramolecular hydrogen bond in the ZE isomer, which is found from the quantum‐chemical calculations including Bader's quantum theory of atoms in molecules analysis. This hydrogen bond results in the increase of δ(¹H‐6) and ¹J(C‐6,H‐6) parameters. The effect of the C–H?N hydrogen bond on the ¹H shielding and one‐bond ¹³C–¹H coupling complicates the configurational assignment of the considered compound because of these spectral parameters. The ¹H, ¹³C and ¹⁵N chemical shifts of the 2‐ and 8‐(CH₃)₂N groups attached to the –C(CH₃)═N– and –CH═N– moieties, respectively, reveal pronounced difference. The ab initio calculations show that the 8‐(CH₃)₂N group conjugate effectively with the π‐framework, and the 2‐(CH₃)₂N group twisted out from the plane of the backbone and loses conjugation. As a result, the degree of charge transfer from the N‐2– and N‐8– nitrogen lone pairs to the π‐framework varies, which affects the ¹H, ¹³C and ¹⁵N shieldings. Copyright © 2012 John Wiley & Sons, Ltd.     

13C shielding scale for MAS NMR spectroscopy

We have performed the direct measurements of ¹³C magnetic shielding for pure liquid TMS, solution of 1% TMS in CDCl₃ and solid fullerene. The measurements were carried out in spherical ampoules exploring the relation between the resonance frequencies, shielding constants and magnetic moments of ¹³C and ³He nuclei. Next the ¹³C shielding constants of glycine, hexamethylbenzene and adamantane were established on the basis of appropriate chemical shifts measured in the solid state. All the new results are free from susceptibility effects and can be recommended as the reference standards of ¹³C shielding scale in the magic angle spinning NMR experiments. Copyright © 2011 John Wiley & Sons, Ltd.     

13C NMR spectra and the structure of dithizone

The structural characteristics of dithizone in the solid state and in solution were studied by a high-resolution¹³C NMR method. A highly symmetrical structure of dithizone was established in the crystalline state, and it was suggested that it exhibits dual behavior in complexation reactions with metal ions.V. I. Vernadskii Institute of Geochemistry and Analytical Chemistry, Russian Academy of Sciences, 117975 Moscow. Translated from Izvestiya Akademii Nauk, Seriya Khimicheskaya, No. 1, pp. 113–117, January, 1992.     

13 C NMR spectra of some indole derivatives

The effect of acyl and carboxyl groups in position 2 or 3 of the indole ring on the¹³C chemical shifts of the ring was studied, -, -, and -Increments of the indole and isatin rings for¹³ C chemical shifts of the substituants at the ring N-atom were determined.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 1, pp. 66–69, January, 1994.     

13C NMR spectra of azolopyridines and their quaternary salts

¹³ C NMR spectra of some azole series have been investigated: 2-pyridylbenzimidazoles, 2-pyridylimidazo [4,5-b]-pyridines, 2-pyridylimidazo[4,5-c]-pyridines, analogous oxazole compounds, as well as their mono- and bisquaternary salts. Some problems, related to the structure of these compounds in solution, have been discussed.V. I. Vernadskii Institute of Geochemistry and Analytical Chemistry, Russian Academy of Sciences, Moscow 117975. Torino University, Italy. Translated from Izvestiya Akademii Nauk, Seriya Khimicheskaya, No. 4, pp. 866–872, April, 1992.     

13C NMR spectra of polycyclic compounds. Bicyclo[2.2.1]heptadiene tetramers

Comparison of experimental and calculated chemical shifts of carbon atoms in¹³C NMR spectra of two isomeric dodecacyclo[14.9.1.1^4,13.1^7,10.0^2,15.0^3,14.0^5,12.0^6,11.0^17,25.0^18,24.0^19,21. 0^20,24]-octacos-8-enes, bicyclo[2.2.1]heptadiene tetramers, confirmed theirexo-trans-exo-trans-exo-endo-andexo-trans-exo-trans-exo-exo-configurations. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 12, pp. 2545–2547, December, 1998.     

The statistical generation of SCS values and interaction factors for the13C NMR spectra of arenes

A new methodology which statistically determines substituent chemical shifts (SCS) and interaction factors of adjacent groups for use in the³C NMR spectroscopy of arenes is described. From a data base of 15,255 signals we have computed several hundred of thesestatistical SCS values (SSCS values), and interaction factors for many common pairs of groups. Some interaction factors for 1,2,3-substitution are also reported. When these SSCS values and interaction factors are used to predict the signal position they are found to give a correlation coefficient of predicted verses observed values of 0.994 with a standard deviation of 1.5 ppm.     

N-Oxides of polychloropyridines.13C NMR study

The effect ofN-oxidation of a series of polychloropyridines on¹³C NMR parameters has been studied. It has been established that inN-oxides of polychloropyridines an electric field through-space effect of theN-oxide group predominates in the shielding of the -carbon atom compared to the other carbon atoms. A linear correlation between¹³C NMR chemical shifts and total charge densities calculated by the MNDO method for the carbon atoms ofN-oxides of polychloropyridines has been found.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 12, pp. 2425–2428, December, 1995.The authors are grateful to V. V. Kolchanov for help in the synthesis of compounds under study.     

Ab initio study of the NMR shielding constants and spin-spin coupling constants in cyclopropene

Summary Ab initio calculations of parameters which characterize the NMR spectrum are presented for the cyclopropene molecule. The London orbitals CHF (or GIAO-CHF, Gauge-Independent Atomic Orbital Coupled Hartree-Fock) results for the shielding constants are in good agreement with the experimental data, accurately determined, and with otherab initio values. The calculations of the NMR spin-spin coupling constants have been performed using the Multiconfiguration Time-Dependent Hartree-Fock (MC TDHF) approach. Different basis sets and MC SCF wavefunctions were used to estimate the accuracy of the results. Good agreement is obtained with the coupling constants estimated using the available experimental data.Dedicated to Professor Werner Kutzelnigg on the occasion of his 60th birthday     

The13C NMR spectra of some polychlorinated dibenzo-p-dioxins. A calculation of13C chemical shifts

The¹³C NMR spectra of a number of polychiorinated dibenzo-p-dioxins (PCDD) were measured. These and previously known spectra were used for the development of a method for calculation of¹³C NMR spectra of chloroaromatics in the framework of a two-particle increment scheme for carbon chemical shifts. The scheme one allows to calculate¹³C chemical shifts for all 75 PCDD.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 4, pp. 760–761, April, 1994.     

13C NMR Spectra of 6-Hydroximinosteroids of the Stigmastane Series

¹³ C NMR spectra were studied and signals of C atoms were assigned for 6-keto- and 6-hydroximinosteroids 1-10.     

13C NMR study of 2,3,4,5-tetraphenylsilole dilithium salt

The complete assignment of the signals in the¹³C NMR spectra of 2,3,4,5-tetraphenyl-1-R¹,R²-1-silacyclopenta-2,4-dienes (R¹=R²=H, Me) and of the dianion of lithium salt [(PhC)₄Si]²⁻·2Li⁺ was carried out by 2D NMR spectroscopy. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 1, pp. 216–218, January, 1999.     

Quantum chemical prediction of the 13C NMR shifts in alkyl and chlorocorannulenes: correction of chlorine effects

Prediction of the ¹³C NMR shifts of sym-pentachlorocorannulene and decachlorocorannulene provided impetus for the development of a correction scheme based on a regression of experimental and quantum chemical data. A training set of 15 compounds (18 carbon signals) comprising carbons atoms bearing 1–4 chlorine atoms leads to an estimated error per chlorine atom of about 10–12 ppm. Specifically, linear regression of the data obtained at B3LYP/cc-pVDZ leads to y = −3.77 + 13.11x, with R = 0.982. Ultimately, experiment and theory converge for sym-pentachlorocorannulene and decachlorocorannulene, the former by correction of the theory, the latter by collecting the proper experimental data. Contribution to the Mark S. Gordon 65th Birthday Festschrift Issue.     

Study of stereospecificity of 1H, 13C, 15N and 77Se shielding constants in the configurational isomers of the selenophene-2-carbaldehyde azine by NMR spectroscopy and MP2-GIAO calculations

In the (1)H and (13)C NMR spectra of selenophene-2-carbaldehyde azine, the (1)H-5, (13)C-3 and (13)C-5 signals of the selenophene ring are shifted to higher frequencies, whereas those of the (1)H-1, (13)C-1, (13)C-2 and (13)C-4 are shifted to lower frequencies on going from the EE to ZZ isomer or from the E moiety to the Z moiety of EZ isomer. The (15)N chemical shift is significantly larger in the EE isomer relative to the ZZ isomer and in the E moiety relative to the Z moiety of EZ isomer. A very pronounced difference (60-65 mg/g) between the (77)Se resonance positions is revealed in the studied azine isomers, the (77)Se peak being shifted to higher frequencies in the ZZ isomer and in the Z moiety of EZ isomer. The trends in the changes of the measured chemical shifts are reasonably reproduced by the GIAO calculations at the MP2 level of the (1)H, (13)C, (15)N and (77)Se shielding constants in the energy-favorable conformation with the syn orientation of both selenophene rings relative to the C = N groups. The NBO analysis suggests that such an arrangement of the selenophene rings may take place because of a higher energy of some intramolecular interactions.     

13C NMR spectroscopy of tautomeric conversions in imidazole compounds

A study has been made of¹³C NMR spectra of several series of imidazoles and their salts in solution and in the solid state. It has been shown that in compounds containing a pyridine ring, prototropic tautomerism on the NMR time scale may be retarded. The possible mechanism of these processes is discussed.V. I. Vernadskii Institute of Geochemistry and Analytical Chemistry, Russian Academy of Sciences, 11795 Moscow. Torino University, Italy. Translated from Izvestiya Akademii Nauk, Seriya Khimicheskaya, No. 2, pp. 299–308, February, 1992.     

Interpretation of13C NMR spectra of 7-substituted 9,11-dideoxy-PGF 1 analogues and their synthons

A full interpretation of¹³C NMR spectra of the methyl esters of 7-hydroxy-and 7-oxo-9,11-dideoxy-PGF ₁ analogues and their synthons is reported.

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Interpretation von¹³C-NMR-Spektren von 7-substituierten 9,11-Dideoxy-PGF₁-Analogen und deren Synthonen

Zusammenfassung Es wird eine vollständige Zuordnung der¹³C-NMR-Resonanzen von den Methylestern der 7-Hydroxy- und 7-Oxo-9,11-dideoxy-PGF ₁-Analogen und ihrer Synthone beschrieben.

     

Characterization of cyclotriveratrylene inclusion compounds by means of solid state13C NMR

Solid inclusion compounds of cyclotriveratrylene (CTV) with benzene, toluene, acetone, tetrahydrofuran, acetic acid and chloroform, as well as two hydrated forms, were prepared and characterized by solid state¹³C NMR. The inclusion process for CTV appears to be quite selective, and in some instance depends critically on the presence or absence of water. A number of different structural types are indicated by the solid state¹³C NMR splitting paterns. For the guests listed above,¹H NMR in solution indicated a guest to host ratio close to 0.5, except for chloroform, for which the ratio is closer to 2.