Search results for "IFT"

Nitrogen-15 NMR Studies on Hydrazines. 2— Substituent Effect Analysis inortho-Substituted Phenylhydrazines and Anilines

1996

15N and 13C NMR spectra of some ortho-substituted phenylhydrazines were measured at natural isotope abundance in DMSO-d6 solutions. The substituent present exerts a larger effect on the chemical shift of the nitrogen atom directly bound to the aromatic ring (N-1), the second one (N-2) showing an attenuated trend of similar sign. Contrary to what observed for para and meta isomers, the cross-correlation between N-1 and N-2 SCS values of ortho-substituted phenylhydrazines is not satisfactory; on the other hand, N-1 SCSs show a reasonably good linear regression with the σR− constants. As expected, no correlation was found between N-1 and C-1 or H-1 SCS values. Correlations between 13C and 15N …

NMR studies of benzoannulation in lithium, sodium and potassium ortho-formylphenolates

2010

Abstract Lithium, sodium and potassium derivatives of (benzo)salicylaldehydes have been prepared and characterized by 1 H and 13 C NMR in order to see how the metal cation and benzoannulation affect spectral parameters. There is no qualitative effect of the alkali metal atom in the compounds studied (from this point of view salicylaldehydes remind β-diketones). On the other hand, 1 H chemical shifts of the hydroxyl and formyl protons and 13 C chemical shifts of C2 (bearing OX, X = H, Li, Na or K) and of that the formyl carbon show the most significant variations being the best indicators of aromatic character of the six-membered quasi-ring of salicylaldehyde. In contrast, C1 (bearing formyl…

Effects of substitutions on cyclopentadienyl rings in complexes with molybdenum-mercury bonds. 95Mo and 199Hg NMR studies

1995

NMR data for 95Mo and 199Hg nuclei have been obtained for new di- and trimetallic complexes Cp′(CO)3MoHgX containing molybdenum-mercury bonds and bulky and/or potentially bifunctional substituted cyclopentadienyl ligands; Cp′=C5HMe2Ph2, C5Me4Bz, C5Bz5, C5H4PPh2 and C5Me4PPh2 (Bz=CH2C6H5; Me =CH3; Ph=C6H5); X=Cp′(CO)3Mo, Cl, Br, 1, SCN. They are discussed within the context of our earlier results reported for analogous complexes with the cyclopentadienyl ligands bearing methyl groups. With the exception of phenyl substituted rings, a rather narrow range of 95Mo chemical shifts is found for the compounds with the same number of different substituents on cyclopentadienyl ligands. An outstandin…

ChemInform Abstract: Methylium Ions with OPV Chains - New NIR Dyes.

2010

Carbinols, which contain three OPV chains, were generated in convergent syntheses. The extension of the conjugation leads to a bathochromic effect that shifts the absorption from the UV into the visible region. The carbinol series has a convergence limit of the absorption at λmax = 415 nm. The corresponding carbenium ions exhibit a stronger bathochromic shift with the increasing number of repeating units in each chain. Thus, NIR dyes were obtained which show a convergence limit at λmax = 879 nm. The charge distribution in the ground state of the carbocations is discussed on the basis of 13C NMR spectroscopic data.

ChemInform Abstract: Bathochromic or Hypsochromic Effects via the Extension of Conjugation: A Study Stilbenoid Squaraines.

2010

Geometric Considerations in Modeling Oxygen Transport Processes in Tissue

1973

Numerical solution of partial differential equations describing transport processes in capillaries and tissue is used for calculation of oxygen transport to brain tissue. Calculation is based on a three-dimensional network model which covers inhomogeneities in capillary blood flow in a relation of 27:1, This study was performed in order to obtain information about the influence of the main physiological parameters on oxygen tension frequency distribution pattern. Following results were obtained: a)Increase (or decrease) of the oxygen consumption rate in tissue to about twice (or half) of the normal case for cerebral grey matter causes an extreme left (or right) shift of the oxygen tension f…

Multinuclear Magnetic Resonance Study of 2,4,6-Triarylpyridines, 1-Methyl-2,4,6-Triarylpyridinium, and 2,4,6-Triarylpyrylium Cations

1995

Abstract The H, 13C, 15N, and 19F NMR spectra of 2,4,6-triarylpyridines, 1-methyl-2,4,6-triarylpyridinium and 2,4,6-triarylpyrylium perchlorates have been studied. The H NMR signals of protons 3(5) in the heteroaromatic ring are deshielded due to the polarization of C-H bonds caused by delocalization of the positive charge in pyridinium and pyrylium cations. Generally, conformational and structural variations affect the 13C NMR chemical shifts of all carbons in the heteroaromatic ring. Those of carbons 3(5) can best be related to the electron-donating or electron-accepting ability of substituents. However, both electronic character of substituents and charge of heteroatom itself are needed …

1H, 13C NMR spectral and single crystal structural studies of toxaphene congeners. Quantum chemical calculations for preferred conformers of 2,5-endo…

2005

Abstract The 1H and 13C NMR chemical shifts for six toxaphene congeners: 2-exo,3-endo,6-exo,8,9,10-hexachloro- (1), 2-exo,3-endo,5-exo,9,9,10,10-heptachloro- (2), 2-exo,3-endo,6-exo,8,9,10,10-heptachloro- (3), 2-exo,3-endo,5-exo,6-endo,8,9,10-heptachloro- (4), 2-exo,3-endo,5-exo,6-endo,8,9,9,10-octachlorobornane (5) and 2,5-endo,6-exo,8,9,9,10,10-octachloro-2-bornene (6) are reported. Their chemical shift assignments have been obtained by means of Pulsed Field Gradient (PFG) Double Quantum Filtered (DQF) 1H,1H correlation spectroscopy (COSY), PFG 1H,13C Heteronuclear Multiple Quantum Coherence (HMQC) and PFG 1H,13C Heteronuclear Multiple Bond Correlation (HMBC) experiments. A single crystal…

Chlorodicyclopentadienyloxoniobium(V) complexes revisited: The origin of the asymmetry in the 1H- and 13C-NMR spectra, X-ray crystal structures and a…

2000

Abstract 1H- and 13C-NMR spectra of chlorodicyclopentadienyloxoniobium(V) complex I and its four 1,1′-dialkyl substituted derivatives II–V have been recorded and assigned based on DQF 1H,1H-COSY and PFG 1H,13C-HMQC and HMBC experiments. Non-equivalences of all cyclopentadienyl protons and carbons in II–V (as reflected by their different 1H- and 13C-NMR chemical shifts) are explained by synchronous and out-of-phase rotations of the substituted cyclopentadienyl rings. A non-equivalence of the methyls in III (1,1′-di-isopropyl) is explained by a detailed inspection of the rotamers of the isopropyl groups. The X-ray structural data show that III and IV (1-methyl-1′-tert-butyl) crystallize in th…

Comparative multinuclear magnetic resonance spectroscopic study of transition metal (Cr, W and Mn) mesitylene tricarbonyls and transition metal (Ru a…

1993

Abstract Three mononuclear 1,3,5-trimethylbenzene (mesitylene) carbonyl transition metal complexes, mesitylene tricarbonyl chromium, (CH 3 ) 3 C 6 H 3 Cr(CO) 3 ( 1 ), mesitylene tricarbonyl tungsten, (CH 3 ) 3 C 6 H 3 W(CO) 3 ( 2 ), mesitylene tricarbonyl manganese tetra-fluoroborate, [(CH 3 ) 3 C 6 H 3 Mn(CO) 3 ]BF 4 ( 3 ); and three clusters, mesitylene nonacarbonyl tetracobalt, (CH 3 ) 3 C 6 H 3 Co 4 (CO) 9 ( 4 ), mesitylene carbido tetradecacarbonyl hexaruthenium, (CH 3 ) 3 C 6 H 3 Ru 6 C(CO) 14 ( 5 ) and carbido heptadecacarbonyl hexaruthenium, Ru 6 C(CO) 17 ( 6 ), have been studied by means of 1 H, 13 C and natural abundance 17 O NMR spectroscopy. Generally, the 1 H and 13 C NMR chemi…