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1

Adenine and Some of Its Analogues in DMSO-d6 Solution: an NMR and GIAO-DFT Study

Dybiec K., Molchanov S., Gryff-Keller A.

Polish Journal of Chemistry

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2009

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Vol. 83, nr 5

857-868

EN

The results of GIAO-DFT calculations [at B3LYP/6-311++G(2d,p) PCM and PBE1PBE/6-311+G(2fd,p) PCM levels] of 13C NMR and 15N NMR parameters have been employed to reinvestigate tautomerism of adenine in DMSO solution. The separate 13C NMR sig nals of N7-H and N9-H adenine tautomers have been observed for the first time. The ex erimental 13C chemical shifts, 3J(C,H) coupling constants and 15N chemical shifts of adenine and three of its methyl derivatives (9MeA, 7MeA and 3MeA) have been quantitatively analyzed using the calculated parameter values. This procedure has provided the solution populations of the predominant adenine tautomers being in agreement with the available literature data. The apparent dependence between the amino group geometry and the chemical shift of the adjacent carbon in 2-aminopyridine system has also been discussed.

2

King Is Naked: Comparison of ab initio and DFT Calculations of Magnetic Shielding of 13C Nuclei in Chloromethanes

Molchanov S., Gryff-Keller A.

Polish Journal of Chemistry

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2007

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Vol. 81, nr 1

137-140

3

1H NMR, 13C NMR and Computational Study of the Structure of Salicylaldehyde Anion in Solution

Horbaczewski M., Szczeciński P., Gryff-Keller A., Molchanov S.

Polish Journal of Chemistry

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2007

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Vol. 81, nr 12

2089-2096

EN

1H NMR and 13C NMR spectra of salicylaldehyde potassium salt in DMF-d7 solution with addition of kryptofix 222 were mea sured. Quantitative comparison of car bon chemical shifts with shielding constants calculated for syn and anti con form ers of salicyl aldehyde an ion [GIAO DFT B3LYP/6-311G(2d,p) PCM] re vealed that in the applied conditions the anti form prevailed. Similar correla tion performed for salicylaldehyde lith ium salt indicated that in this case the syn conformer dominated. Analysis of experimental and calculated J(1H,13C) and J(1H,1H) values supported above conclusions.

4

1H NMR, 13C NMR and Computational DFT Study of the Structure of 2-Acylcycloalkane-1,3-diones in Solution

Szczeciński P., Gryff-Keller A., Molchanov S.

Polish Journal of Chemistry

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2007

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Vol. 81, nr 8

1449-1455

EN

1H and13C NMR spectra of 2-acylcyclopentane-1,3-dione [acyl = formyl (1); acetyl (2)] and 2,6-dioxocyclohexanecarboxylic acid (3) have beenmeasured. The optimummolecular structures of endo- and exo-enolic forms of investigated objects in solution have been found using DFT method with B3LYP functional and 6-311G(2d,p) basis set. The theoretical values of the NMR parameters have been then calculated using GIAO-DFT method with the same functional and basis set. The theoretical data obtained for compounds 1–3 have been used to interpret their experimental NMR spectra in terms of the equilibrium between different tautomers. It has been found that for investigated triketones an endo-tautomer overwhelmingly prevails.

5

Main Factors Governing Chemical Shifts of Carbon and Nitrogen in Cyano Group. An Experimental and Theoretical Study

Molchanov S., Gryff-Keller A.

Polish Journal of Chemistry

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2006

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Vol. 80, nr 7

1031-1038

EN

The feasibility of a description of magnetic shielding of carbon and nitrogen nuclei of cyano group in various cyano compounds as a net result of the interplay of different structural factors is discussed. Analysis of experimental data and DFT GIAO calculations of shielding constants have shown that the main factors governing the carbon chemical shifts are the heavy-atom and inductive effects, although the resonance and steric properties of a substituent are also of some importance. On the other hand, the shielding of the cyano nitrogen is connected mainly with the redistribution of _-electrons within the cyano group, which is the result of mesomeric interaction, and, to a lesser extent, with the inductive properties of the substituent. The steric and heavy-atom effects of the substituent seem to be irrelevant for the shielding of cyano nitrogen.

6

Creatinine and Creatininium Cation in Water Solution. Tautomerism and Quantitative Interpretation of the Solution Acidity Effect on 1H, 13C and 14 N NMR Chemical Shifts

Kotsyubynskyy D., Molchanov S., Gryff-Keller A.

Polish Journal of Chemistry

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2004

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Vol. 78 / nr 2

239-248

EN

1H, 13C and 14N NMR chemical shifts for creatinine in water solutions of various acidity have been measured. Analysis of these data enabled determination of the acidity constant of creatininium cation and the chemical shifts of the neutral and protonated forms of creatinine. Molecular energies and carbon and nitrogen magnetic shielding constants for various tautomeric structures of the investigated species have been calculated using the quantum chemistry method GIAO DFT B3LYP/6-311++G(2d,p). Compilation of the available experimental and theoretical results has provided additional information on the problem of tautomerism of this important biological molecule.

7

Effect of planar substituents on magnetic shielding tensors of sp-hybridized carbon nuclei in substitueted acetylenes - a GIAO-CHF study

Jackowski K., Molchanov S., Gryff-Keller A.

Bulletin of the Polish Academy of Sciences. Chemistry

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2000

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Vol. 48, No. 1

77-80

EN

The magnetic shielding tensors for sp-hybridized carbons in a series of acetyl-enic compounds XC=CH (X = H, NH2, OMe, NMe2) Ph, CHO, CC1O and NO2) have been calculated using the GIAO-CHF method and the standard 6-31G** basis set. The substituent effect has appeared to be large but independent of the 7r-electronic properties of the substituent.

8

Multinuclear spin relaxation study on mercury(II) cyanide

Molchanov S., Gryff-Keller A.

Bulletin of the Polish Academy of Sciences. Chemistry

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1999

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Vol. 47, No. 1

83-88

EN

Following coupling constants for Hg(CN)2 in DMSO solution have been measured: 1J(13C-199Hg), 1 J(13C-15N), 2 J (199Hg-15N). The longitudinal (13)C and (15)N relaxation times and transverse (13(C relaxation times at two magnetic fields, and additionally the longitudinal (199)Hg relaxation time for 13C or 15(N) enriched samples have also been measured. Quantitative interpretation of those data has delivered the values of the reori-entation rate of the solute molecule and the shielding anisotropy parameters of carbon and nitrogen nuclei. Some earlier literature results concerning water solution of the inves-tigated molecule have also been commented.