Nuclear resonance vibrational spectra of five-coordinate imidazole-ligated iron(II) porphyrinates

Nuclear resonance vibrational spectra have been obtained for six five-coordinate imidazole-ligated iron(II) porphyrinates, [Fe(Por)(L)] (Por = tetraphenylporphyrinate, octaethylporphyrinate, tetratolylporphyrinate, or protoporphyrinate IX and L = 2-methylimidazole or 1,2-dimethylimidazole). Measurements have been made on both powder and oriented crystal samples. The spectra are dominated by strong signals around 200-300 cm(-1). Although the in-plane and out-of-plane vibrations are seriously overlapped, oriented crystal spectra allow their deconvolution. Thus, oriented crystal experimental data, along with density functional theory (DFT) calculations, enable the assignment of key vibrations in the spectra. Molecular dynamics are also discussed. The nature of the Fe-N(Im) vibrations has been elaborated further than was possible from resonance Raman studies. Our study suggests that the Fe motions are coupled with the porphyrin core and peripheral groups motions. Both peripheral groups and their conformations have significant influence on the vibrational spectra (position and shape).     

Nuclear magnetic resonance studies of sulfur inversion in bis(cyclopentadienyl)-molybdenum and -tungsten complexes with dithioethers

The metallocene thioether derivatives [Cp₂M(MeSCH₂CH₂SMe)][PF₆]₂ (1, M = MO; 2, M = W), [Cp₂Mo(SCH₂CH₂SMe)][PF₆] (3) and [Cp₂M(SCH₂CH₂S)] (4, M = Mo; 5, M = W) exhibit temperature-dependent fluxional behavior in solution, owing to the pyramidal sulfur inversion process. The activation energies for this process were determined from proton band-shape analysis in the cases of 1 (54.9 ± 2 kJ mol⁻¹), 2 (51.2 ± 4.6 kJ mol⁻¹) and 3 (30.0 ± 3.1 kJ mol⁻¹). Extended Hückel calculations on related model complexes suggest that local inversion at the sulfur atoms, rather that an inversion of the complete S---C---C---S chain, is responsible for the observed fluxional behaviour.     

13C nuclear magnetic resonance spectra of arylthallium(III) bis(trifluoroacetates)

¹³C chemical shifts and ¹³C? ²⁰⁵Tl spin–spin coupling constants are reported for phenylthallium(III) bis(trifluoroacetate) and some of its mono- and dimethyl derivatives. The signs of ⁿJ(¹³C, ²⁰⁵Tl) relative to ⁿ⁺¹J(¹H, ²⁰⁵Tl) are determined by offresonance decoupling of protons.     

Organometallic derivatives of the transition elements : II. Proton magnetic resonance spectra of substituted bis(arene)chromium(0) complexes

The proton magnetic resonance spectra of a series of bis(arene)chromium(0) complexes have been investigated. Simple first order spectra are obtained in most cases, for which chemical shift assignments are reported. A significant reduction in J(HH)-values, relative to the free ligand, are observed for the complexed arenes; H---H coupling is limited to adjacent hydrogen atoms. In fluorobenzene complexes, H---F coupling is so diminished as not to be observed in the majority of our spectra. Meta disubstituted arenes, in which the substituents are not identical, yield two diastereomeric bis(arene)chromium(0) complexes from the metal atom synthesis which can be distinguished on the basis of their PMR spectra.     

Electronic spectra and electrochemical properties of bis(dimethylglyoximato)iron(II) complexes containing axialN-heterocyclic ligands

Gaussian analysis of the electronic spectra of 25 bis(dimethylglyoximato)iron(II) complexes containing axialN-heterocyclic ligands are discussed and comparisons made with the spectra of the corresponding [Fe(CN)₅L]^3– complexes. The energies of the metal-to-axial and metal-to-equatorial ligand charge-transfer transitions exhibit opposite trends, correlating with the electronic properties of the axial ligands, and with the redox potentials of the Fe^II/Fe^III couple.     

Nuclear magnetic resonance spectra of pyrido- and azapyridocyanines

The nuclear magnetic resonace spectra of six pyridocyanines, four azapyridocyanines, one monoquaternized 2,4′-dipyridylamine and two dipyridylamines were measured and fully analyzed. The spectra of the 2,2′-pyrido- and azapyridocyanines support previously published results that these dyes exist in the all-trans form and not in the mono-cis form, as stated by others. Strong evidence was obtained that N,N′-ethylene-2,2′-pyridocyanine is twisted. The spectra of dyes with p-connected pyridine rings indicate that these nuclei may rotate around the bond between the meso group and the p-position. Relative chemical shifts in the spectra of the homologous pyrido- and azapyridocyanines can be explained by electronic effects rather than by magnetic anisotropy of the aza group or changes in ring currents.     

Nuclear magnetic resonance spectra of substituted tetraphenylmethylenediphosphine dioxides

Conclusions We studied nuclear magnetic resonance spectra of substituted dioxides of tetraphenylmethylenediphosphine in a medium of trifluoroacetic acid or chloroform. The chemical shifts measured in chloroform satisfactorily agree with Hammett's . Trifluoroacetic acid levels the effect of substituents.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 2, pp. 419–421, February, 1968.     

Synthesis of asymmetrical bis(arene) iron complexes

Visible light irradiation of the [(η-C₆H₇)Fe(η-C₆H₆)]⁺ cation (1) in CH₂Cl₂ in the presence of alkyl-substituted benzenes results in arene exchange forming the [(η⁵-C₆H₇)Fe(η-C₆R₆)]⁺ cations (2a–d: C₆R₆ is toluene, p-xylene, mesitylene, and durene). The mixed bis(arene) [(η-C₆H₆)Fe(η-C₆R₆)]²⁺ iron complexes (3a–d) were synthesized by hydride ion abstraction from 2a–d by [Ph₃C]⁺. Dedicated to Academician G. A. Abakumov on the occasion of his 70th birthday. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 9, pp. 1864–1865, September, 2007.     

Nuclear magnetic resonance spectra under chemical polarization conditions

Russian Chemical Bulletin -     

Nuclear magnetic resonance studies of helical dipyrromethene-zinc complexes

[formula: see text] Analysis of helical chirality within dinuclear dipyrromethene-Zn(II) complexes has been achieved with the use of 1H NMR spectroscopy. The use of AgFOD and chiral lanthanide shift reagents gives fully resolved resonances attributable to two diastereomeric helical complexes.     

Nuclear magnetic resonance spectra of furan derivatives of IV B group elements (review)

Electronic and steric effects in furan derivatives were studied by the method of ¹H, ¹³C, ¹⁷O, and ²⁹Si NMR spectroscopy. The characteristic features of the influence of substituents on the screening and spin-spin interaction of ring nuclei in -substituted derivatives of furan in the presence of a second -substituent have been noted.Dedicated to Prof. A. R. Katritsky on his 65th birthday.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 7, pp. 879–890, July, 1993.     

Nuclear magnetic resonance spectra of codeine and isocodeine derivatives

The NMR spectra of a spiro oxirane ( 1 ) derivative of codeinone, codeine ( 2 ), isocodeine ( 3 ), 6-methylcodeine ( 4 ) and 6-methylisocodeine ( 5 ) were compared. NOE and double-resonance experiments were used to confirm the conformation of 1 , and the configuration about C-6 of 6-methylcodeine and 6-methylisocodeine. An interchange of the chemical shifts of the olefinic protons in 1 was noted, as compared with those in all of the other compounds. This interchange could be attributed to the bond anisotropies of the oxirane moiety.     

Nuclear magnetic resonance spectra of polyalkylindoles obtained by transformations of 3-nitropyridenium salts

Data are correlated on the ¹E and ¹³C NMR spectra of a representative series of polyalkylindoles obtained by the reaction of alkyl-substituted 3-nitropyridinium salts with ketimines. It has been shown that the use of a combined approach to the interpretation of the ¹H and ¹³C NMR spectra enables reliable information to be obtained on the structure of these previously unknown indole derivatives. The long range ¹³C-H coupling constants give particularly valuable information. A reliable demonstration of the structure of the reaction products is the basis for establishing the route of the indolization.Dedicated to Professor A. R. Katritzky on his 65th birthday.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 7, pp. 899–906, July, 1993.     

Proton nuclear magnetic resonance spectra ofOrtho-metalated alkyne-carbonyltriosmium complexes

Summary The¹H nuclear magnetic resonance spectra of Os₃(CO)₈(Ph₂C₂)₂ and Os₃(CO)₈[(p-ClC₆H₄)₂C₂]₂ are described. In these metal cluster complexes theortho-metalation involves phenyl groups linked to a cyclopentadiene ring.     

Nuclear magnetic resonance of Zn(II) complexes with 2,2′-bipyridine

The complexes Zn(bipy)Cl₂ and Zn(bipy)₂Cl₂ as well as 2,2′-bipyridyl in aqueous solution (D₂O) have been examined by the NMR method. The presence of the monocationic bipy D⁺ form in aqueous bipyridyl solution has been found. The changes of chemical shifts of bipyridyl protons for complexes Zn(bipy)₃Cl₂ and Zn(bipy)Cl₂ have confirmed explicitly the essential influence of diamagnetic currents on the NMR spectrum of Zn(bipy)₃Cl₂. The comparison of the spectra of 2,2′-bipyridyl (in CH₃OH) and of Zn(bipy)Cl₂ may also suggest the presence of the nonbonding metal-proton 6 interaction.