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1.
The 14N nuclear quadrupole resonance (NQR) quadrupole coupling tensors of picolinic, nicotinic, isonicotinic and dinicotinic acids have been determined. Two different 14N quadrupole coupling constants 1007 kHz and 4159 kHz have been observed for picolinic acid demonstrating the presence of both protonated and non-protonated nitrogen atoms in this system in the solid. Only one set of non-protonated 14N NQR lines has been observed in other pyridinecarboxylic acids demonstrating the absence of the protonated zwitter ion forms observed in picolinic acid. The non-protonated 14N quadrupole coupling constant is the highest for the non-protonated nitrogen in picolinic acid and decreases to 3774 kHz in nicotinic acid and 3570 kHz in isonicotinic acid. It is the lowest in dinicotinic acid where the corresponding 14N quadrupole coupling constant is 2794 kHz. The observed anomalous decrease in the 14N quadrupole coupling constant of dinicotinic acid with decreasing temperature is tentatively explained as reflecting the increase in the residence time of the N–H?O bonded proton in the potential well close to the nitrogen. 相似文献
2.
A coupling equation relating the quadrupole coupling constant (e2
Qq
zz
) to the asymmetry parameter (η) of the electric field gradient for a series of cobaltocenium derivatives (59Co NQR) is derived. The estimates of the correlation times of “slow” modulations of electron motions by tunneling processes
lie in the range from 10−12 to 10−14 s. This corresponds to the interval of the characteristic times of nuclear motions.
Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 10, pp. 1919–1923, October, 2007. 相似文献
3.
L. A. Zemnukhova G. A. Fedorishcheva R. L. Davidovich 《Russian Chemical Bulletin》1996,45(10):2369-2372
Variations of the shape of123Sb NQR lines in phase transitions in a new ionic conductor, potassium pentafluoroantimonite(ui), in the temperature range from 77 to 430 K were studied. The transition from a paraelectric phase to a commensurate phase occurs via incommensurate and commensurate-modulated phases.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 10, pp. 2497–2500, October, 1996. 相似文献
4.
14N chemical shifts and linewidths were determined for NO
3
–
and NH3 in liquid ammonia solutions of thallium nitrate at concentrations between 0.07 and 10 M. The concentration dependences of the14NO
3
–
shift and linewidth are consistent with the presence of C2v ion pairs at a 2:1 mole ratio of NH3 to TINO3 and C3v ion pairs at mole ratios of 3:1 or higher. Previous studies had indicated the formation of ion pairs at low concentrations. The small value of the14NO
3
–
linewidth below 1 M suggests that these are contact ion pairs. Studies of the14NH3 linewidth as a function of thallium salt concentration indicate slow solvent exchange at very high concentrations.14NH3 exhibits a downfield shift upon incorporation into the solvation sphere of the Tl+NO
3
–
ion pair, in constrast to upfield shifts reported for complexation with transition metal cations. 相似文献
5.
L. A. Zemnukhova R. L. Davidovich G. A. Fedorischeva 《Russian Chemical Bulletin》1994,43(10):1736-1737
The temperature dependence of the frequencies of121Sb nuclear quadrupole resonance in the spectra of M2Sb2SO4F6 (M = K, Rb, NH4) was studied in the temperature range from 77 to 340 K. A secondary phase transition was found above 320 K for (NH4)2SO4F6.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 10, pp. 1831–1833, October, 1994.This study was sponsored by the Russian Foundation for Basic Research (Grant No. 93-03-4394). 相似文献
6.
M. Monajjemi B. Honarparvar S. M. Nasseri M. Khaleghian 《Journal of Structural Chemistry》2009,50(1):67-77
In this paper extensive systematic computational study has been carried out to justify hydrogen bonding interactions and their influence on the oxygen, nitrogen and hydrogen NQR and NMR parameters of the anhydrous and monohydrated guanine crystal structures at two different levels, B3LYP and MP2, using 6-311++G** and D95** basis sets. These theoretical data have been compared with experimental NMR and NQR measurements. For further investigation, results of cluster calculation have been compared with that of a single molecule. Our theoretical NQR and NMR parameters of 17O, 15N and 2H atoms of anhydrous and monohydrated guanine exhibited extreme sensitivity to electron distribution around mentioned nuclei caused by cooperative influences of various types of hydrogen bonding interactions. Fortunately, our calculated isotropic shielding values and CS tensors for the 17O and 15N nuclei as well as obtained 14N-NQR parameters are in excellent agreement with experimental data. Therefore, we can undoubtedly conclude that for anhydrous and monohydrated guanine tetrameric clusters including intermolecular interactions, our theoretical estimates are in better agreement with observed experimental values than those in which these interactions have been ignored. 相似文献
7.
Inter- and intramolecular nuclear magnetic quadrupole relaxation measurements have been used to study the system methanol (CH3OH)+ N,N-dimethylformamide (DMF)+NaI at 25°C. The dynamic behavior of the solvent molecules was investigated, throughout the composition range of the binary mixtures, by means of
14
N relaxation of DMF and
2
H of methanol-d
1
(CH
3
OD). The intermolecular relaxation of
23
Na+ in pure DMF was used to obtain information about the symmetry of the solvent electric dipole arrangement in the solvation sphere of the ion. The investigation of preferential solvation around Na+ in the binary mixtures was carried out by means of
23
Na+ relaxation measurements using, for the first time, both the CH
3
OH/CD
3
OD and the DMF/DMF-d
7
dynamic isotope effect. The results show that, throughout the composition range, there is preferential solvation by DMF. Furthermore, the use of the isotope effects of both components allowed for the first time a basic check of the reliability of the method since we obtained two independent sets of data for the composition of the Na+ solvation shell in the mixtures. The consistency of the two separate data sets demonstrates that the application of the dynamic isotope effect represents a powerful tool in preferential solvation studies. 相似文献
8.
Dimethyl dihydro-1,2,4,5-tetrazine-3,6-dicarboxylate can exist either in 1,2- or 1,4-dihydro tautomeric forms. The 15N NMR spectra of dimethyl dihydro-1,2,4,5-tetrazine-3,6-dicarboxylate were measured at the 15N natural abundance level as well as in 15N doubly labelled selectively and in 15N completely labelled compounds (20% 15N). The J(15N,15N) value was determined in 15N completely labelled compounds (20% 15N) using 1D 15N INADEQUATE and was found to be 12.2 ± 0.2 Hz in deuteriochloroform, acetonitrile-d3, DMSO-d6 and CD3OH. Very similar 15N chemical shifts and 1J(15N,1H) values were also observed in all the solvents. This indicates that compound 1 exists completely in the 1,4-dihydro tautomeric form (i.e., as dimethyl 1,4-dihydro-1,2,4,5-tetrazine-3,6-dicarboxylate) in all the solvents tested. 相似文献
9.
The present study illustrated the stability of linkage isomers of [Fe(CO)4(NCS)]? and [Fe(CO)4(SCN)]? by the use of PBE quantum method. It also investigated the polarity of solvent effect on dipole moment, structural parameters, and frontier orbital energies of complexes. The results indicated that the polarity of solvent had a significant effect on the frontier orbital energies and HOMO-LUMO gap. The character of Fe-C bonds of molecules was analyzed by Natural bond orbital (NBO) analysis. Back-bonding effect in these bonds was explored with calculation of quadrupole polarization of carbon atom by QTAIM analysis. Also, 14N NQR parameters were used for the illustration of Fe-NCS and Fe-SCN bonds. 相似文献
10.
The nuclear quadrupole coupling constants at nitrogen centers have been computed for N2O3 and FNO by employing the complete-active-space self-consistent field, internally contracted multireference configuration interaction and single-configuration coupled-cluster methods with correlation-consistent basis sets at the levels of attainable accuracy. To examine the overall quality of the wave functions used in our calculations, also electric dipole moments and potential energy characteristics were calculated and compared with available experimental and recent theoretical data. The effects of the choice of the basis set and reference configuration space were investigated. The robust changes in the electric field gradients occurring in the course of complex formation from isolated subunits were interpreted in terms of wave function composition. Our calculations confirm the assignment of the 14N nuclear quadrupole coupling constants to nuclear centers in N2O3 provided by the microwave measurements of Cox et al. [A.P. Cox, J. Randell, A.C. Legon, Chem. Phys. Lett. 126 (1986) 481.]. 相似文献
11.
3-Methylfurazans with nitrogen-containing substituents at position 4 were studied by 1H, 13C, and 14N NMR spectroscopy. A correlation between the chemical shifts in 13C NMR spectra of these furazans and monosubstituted benzenes with the same substituents was found. The increments for a number of furazan-containing substituents were determined for the first time. 相似文献
12.
B. I. Ugrak Yu. A. Manaev V. P. Perevalov S. A. Shevelev 《Russian Chemical Bulletin》1992,41(11):2012-2017
The15N NMR chemical shifts and15N-1H SSCCs are presented for substituted N-methylpyrazoles with substituents such as CH3, NO2, Br, Cl, NH2, O=CNH2, O=CPh, and COOH at the carbon atoms. The15N chemical shifts of the cyclic atoms of nitrogen and the nitro groups are discussed as well as the geminal and vicinal SSCCs of the ring nitrogen atoms with the hydrogen atoms of the CH and CH3 fragments.N. D. Zelinskii Institute of Organic Chemistry, Russian Academy of Sciences, 117334 Moscow. D. I. Mendeleev Chemico-Technological Institute, Moscow, Translated fromIzvestiya Akademii Nauk, Seriya Khimicheskaya, No. 11, pp. 2554–2561, November, 1992. 相似文献
13.
V. N. Yarovenko M. M. Krayushkin O. V. Lysenko L. M. Kustov I. V. Zavarzin 《Russian Chemical Bulletin》1994,43(3):402-404
A new synthetic method for the preparation of15N-labeled nitriles from nonlabeled nitriles is proposed.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 3, pp. 444–446, March, 1994. 相似文献
14.
《Analytical letters》2012,45(15):3111-3130
ABSTRACT Compound independent calibration (CIC) can be used to measure stable isotopically labeled molecules and their metabolites. This study was designed to demonstrate that gas chromatography coupled to atomic emission detection and CIC are useful analytical tools for the specific and quantitative determination of 13C and 15N labeled caffeine and its metabolites. These labeled compounds can be measured by monitoring either 13C or 15N atomic emission lines and using only one calibration function from one of the analytes. This method can be helpful when it is difficult or impossible to obtain an authentic reference material, which is often the case in metabolic studies. 相似文献
15.
I. A. Grigor'ev M. A. Voinov M. A. Fedotov 《Chemistry of Heterocyclic Compounds》2005,41(9):1134-1138
Derivatives of 3-imidazoline 3-oxide have been studied by 14N and 17O NMR methods. Regularities of the influence of substituents and of a hydrogen bond on chemical shifts have been made apparent.
The range of changes of the chemical shifts of the nitrogen and oxygen nuclei of the nitrone group has been determined. Both
in the 17O and in the 14N NMR spectra the signals of the amino derivatives are the highest field signals for the nitrone group, and the lowest field
signals are the signals of the cyano derivatives in the series of derivatives investigated. Depending on the substituent (from
amino to cyano group) the 17O chemical shifts varied over a range ∼155 ppm, but the interval of change of the 14N chemical shifts for the same substituents was ∼110 ppm.
__________
Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 9, pp. 1336–1341. September, 2005. 相似文献
16.
Yu. A. Strelenko T. I. Godovikova E. L. Ignat'eva 《Chemistry of Heterocyclic Compounds》2002,38(5):547-552
Analysis of the 14N and 15N NMR spectroscopic data of 2-methyl-4,5-dinitro-1,2,3-triazole and of substituted 2-methyl-4(5)-nitro-1,2,3-triazole 1-oxides has shown the possibility of applying them for confirmation of the structures of the studied compounds. 相似文献
17.
D. L. Lipilin E. E. Karslyan A. M. Churakov Yu. A. Strelenko V. A. Tartakovsky 《Russian Chemical Bulletin》2005,54(4):1013-1020
Heating of 2-(alkyl-NNO-azoxy)-1-azidobenzenes in boiling benzene gave 2-alkyl-benzotriazole 1-oxides (Alk = Me, Et, Pri, and But). This first-order reaction involves an earlier unknown intramolecular interaction between the azido and azoxy groups with
simultaneous release of molecular nitrogen. The cyclization rate increases in the following sequence of the alkyl groups:
Me < Et < Pri < But. Complete assignment of the signals in the 1H, 13C, and 14N NMR spectra of 2-alkylbenzotriazole 1-oxides was performed.
Dedicated to Corresponding Member of the Russian Academy of Sciences E. P. Serebryakov on the occasion of his 70th birthday.
__________
Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 4, pp. 989–996, April, 2005. 相似文献
18.
A dependence between the quadrupole coupling constants (e
2
Qq
zz
) and the asymmetry parameters of the electric field gradient (η) for the antimony atoms in the complex [SbF5]2− anions of M2SbF5 pentafluoroantimonites (M=Na, K, Rb, Cs, NH4, Ti, and Et2NH2) was revealed from the123Sb NQR spectra at 77 K.
Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 10, pp. 1988–1990, October, 1998. 相似文献
19.
《Analytical letters》2012,45(12):2369-2376
Abstract An 15N isotope analyser has been assembled for the quantitative determination of the percentage abundance of 15N isotope in nitrogen gas employing molecular optical emission spectroscopic technique. The (2,0) band of the second positive system of N2 was excited in a high frequency discharge. The band heads of the isotopic species 14N14N and 14N15N molecules were resolved using a 0.5 m monochromator and their intensity peaks were measured. The ratio of the peak heights enabled the quantitative determination of 15N in the N2 sample. The performance of the isotope analyser assembled was evaluated and it was found to be quite good as inferred from the analysis of primary standards. The analytical error in the 15N concentration-range 0.36 to 24% is <6% and rsd is <4%. A salient feature of the method adopted is that it is direct and does not call for the use of comparision standards. 相似文献
20.
The electric field gradients (EFG’s) at the nucleus are calculated as a function of internuclear separation in the X2Σg+ and B2Σu+ electronic states of the nitrogen molecule cation using the internally contracted multireference configuration interaction (icMRCI) method. The EFG’s and potential energy functions (PEF’s) are used to estimate the 14N nuclear quadrupole coupling constants (NQCC’s) in the two electronic states as functions of vibrational and end-over-end rotational quantum numbers. The dependences of the computed constants on the basis set and reference configuration space are investigated. Since no counterpart for comparison of the calculated NQCC’s exists, the N2+ results are supported by analogous calculations on the X1Σg+ and A3Σu+ states of N2, for which established data are available. The overall good quality of the icMRCI wave functions is further corroborated by a favorable agreement of spectroscopic constants derived from the corresponding PEF’s and experimental data. Variations of the EFG with internuclear separation are explained in terms of wave function composition, and used for gaining specific insight into the chemical bonding in N2+ and N2. 相似文献