NMR, IR, Mössbauer and quantum chemical investigations of metalloporphyrins and metalloproteins

2001 ◽  
Vol 05 (03) ◽  
pp. 323-333 ◽  
Author(s):  
LORI K. SANDERS ◽  
WILLIAM D. ARNOLD ◽  
ERIC OLDFIELD
Keyword(s):  
Chemical Shift ◽  
Electric Fields ◽  
Heme Proteins ◽  
Density Functional ◽  
Chemical Shifts ◽  
Coupling Constants ◽  
Chemical Shift Tensors ◽  
X Ray ◽  
X Ray Crystallography ◽  
Isotropic Chemical Shifts

We review contributions made towards the elucidation of CO and O 2 binding geometries in respiratory proteins. Nuclear magnetic resonance, infrared spectroscopy, Mössbauer spectroscopy, X-ray crystallography and quantum chemistry have all been used to investigate the Fe –ligand interactions. Early experimental results showed linear correlations between 17 O chemical shifts and the infrared stretching frequency (νCO) of the CO ligand in carbonmonoxyheme proteins and between the 17 O chemical shift and the 13CO shift. These correlations led to early theoretical investigations of the vibrational frequency of carbon monoxide and of the 13 C and 17 O NMR chemical shifts in the presence of uniform and non-uniform electric fields. Early success in modeling these spectroscopic observables then led to the use of computational methods, in conjunction with experiment, to evaluate ligand-binding geometries in heme proteins. Density functional theory results are described which predict 57 Fe chemical shifts and Mössbauer electric field gradient tensors, 17 O NMR isotropic chemical shifts, chemical shift tensors and nuclear quadrupole coupling constants (e2qQ/h) as well as 13 C isotropic chemical shifts and chemical shift tensors in organometallic clusters, heme model metalloporphyrins and in metalloproteins. A principal result is that CO in most heme proteins has an essentially linear and untilted geometry (τ = 4 °, β = 7 °) which is in extremely good agreement with a recently published X-ray synchrotron structure. CO / O 2 discrimination is thus attributable to polar interactions with the distal histidine residue, rather than major Fe–C–O geometric distortions.

Probing solid iminobis(diorganophosphine chalcogenide) systems with multinuclear magnetic resonance

2009 ◽  
Vol 87 (1) ◽  
pp. 348-360 ◽  
Author(s):  
Bryan A Demko ◽  
Roderick E Wasylishen
Keyword(s):  
Solid State ◽  
Chemical Shift ◽  
Solid State Nmr ◽  
Magnetic Shielding ◽  
Chemical Shift Tensors ◽  
X Ray ◽  
X Ray Crystallography ◽  
Shielding Tensor ◽  
Nuclear Magnetic Shielding Tensors ◽  
Nuclear Magnetic

A 31P and 77Se solid-state NMR investigation of the iminobis(diorganophosphine chalcogenide) HN(R2PE)2 (R = Ph,iPr; E = O, S, Se) systems is presented. The NMR results are discussed in terms of the known HN(R2PE)2 structures available from X-ray crystallography. The phosphorus chemical shift tensors are found to be sensitive to the nature of the alkyl and chalcogen substituents. The nature of the R group also influences the selenium chemical shift tensors of HN(R2PSe)2 (R = Ph, iPr), which are shown to be sensitive to hydrogen bonding in the dimer structure of HN(Ph2PSe)2 and to the presence of disorder in the case of HN(iPr2PSe)2. Scalar relativistic ZORA DFT nuclear magnetic shielding tensor calculations were performed yielding the orientations of the corresponding chemical shift tensors. A theoretical investigation into the effect of the E-P···P-E “torsion” angle on the phosphorus and selenium chemical shift tensors of a truncated HN(Me2PSe)2 system indicates that the electronic effect of the alkyl group on the respective nuclear magnetic shielding tensors are more important than the steric effect of the E-P···P-E torsion angle.Key words: iminobis(diorganophosphine chalcogenide), solid-state NMR, 31P NMR, 77Se NMR, ZORA DFT.

Measurement and calculation of 13C chemical shift tensors in α-glucose and α-glucose monohydrate

2011 ◽  
Vol 89 (7) ◽  
pp. 737-744 ◽  
Author(s):  
Darren H. Brouwer ◽  
Kevin P. Langendoen ◽  
Quentin Ferrant
Keyword(s):  
Solid State ◽  
Chemical Shift ◽  
Quantum Chemical ◽  
Density Functional ◽  
Chemical Shifts ◽  
Chemical Calculation ◽  
Hydrogen Atoms ◽  
Chemical Shift Tensors ◽  
Experimental Values ◽  
Crystalline Forms

The 13C chemical shift tensors of two crystalline forms of glucose (α-glucose and α-glucose·H2O) were determined from one-dimensional (1D) and two-dimensional (2D) solid-state nuclear magnetic resonance (NMR) spectroscopy experiments. The experimental values determined from 1D and 2D methods are in very good agreement. Quantum chemical calculations were also carried out using the gauge-including projector augmented wave (GIPAW) method for plane-wave density functional theory (DFT) as implemented in the CAmbridge Serial Total Energy Package (CASTEP). The calculated 13C chemical shifts were found to be in excellent agreement with experimental values for crystal structures that had their hydrogen atoms optimized and after an appropriate calibration was applied to convert calculated chemical shieldings into chemical shifts. The work presented here lays an important foundation for future solid-state NMR and quantum chemical calculation investigations of the various crystalline forms of cellulose.

Solid-state nuclear magnetic resonance studies of triphenylsilyl-, triphenyltin-, and triphenyllead(pentacarbonyl)manganese(I) complexes

1999 ◽  
Vol 77 (11) ◽  
pp. 1892-1898 ◽  
Author(s):  
Dharamdat Christendat ◽  
Ian S Butler ◽  
Denis FR Gilson ◽  
Frederick G Morin
Keyword(s):  
Solid State ◽  
Chemical Shift ◽  
Dipolar Coupling ◽  
Chemical Shifts ◽  
Chemical Shift Anisotropy ◽  
Coupling Constants ◽  
Spin Coupling ◽  
Chemical Shift Tensors ◽  
Lead Compounds ◽  
Spin Spin Coupling

The solid-state CP MAS (29Si, 119Sn, and 207Pb) NMR spectra of the triphenylsilyl-, triphenyltin-, and triphenyllead(pentacarbonyl)manganese(I) complexes, (Ph3E)Mn(CO)5 (E = Si, Sn, Pb), have been analyzed to give the chemical shifts, one-bond spin-spin coupling constants, 1JE-Mn, the "effective-dipolar" coupling constants (D - ΔJ/3), the chemical shift tensors, and the spin-spin anisotropy (ΔJ), where the analysis permits. For the tin and lead compounds, three and four sets of chemical shifts, respectively, were observed, and two different polymorphs occur for the lead complex, depending on the solvent used for recrystallization. The average values of the reduced coupling constants, 1KMn-Si (2.64 × 1020 T2 J-1), 1KSn-Mn (1.25 × 1020 T2 J-1), and 1KPb-Mn (4.18 × 1020 T2 J-1) showed a linear correlation with the s-electron densities at the respective metal nuclei. The principal components of the chemical shift tensors have been determined for the tin and lead compounds.Key words: manganese-group-14 compounds, solid-state 29Si, 119Sn, and 207Pb CP MAS NMR, spin-spin coupling, chemical shift anisotropy, quadrupole coupling.

31P chemical shift anisotropies of trimethyl- and triphenylphosphine-substituted Group 6 metal pentacarbonyl complexes

1998 ◽  
Vol 76 (9) ◽  
pp. 1280-1283 ◽  
Author(s):  
Jordan H Wosnick ◽  
Frederick G Morin ◽  
Denis FR Gilson
Keyword(s):  
Chemical Shift ◽  
Reasonable Agreement ◽  
Chemical Shifts ◽  
Chemical Shift Anisotropy ◽  
Coupling Constants ◽  
Torsion Angles ◽  
Chemical Shift Tensors ◽  
Group 6 ◽  
Phenyl Rings ◽  
The One

The 31P chemical shift tensor components and anisotropies of the trimethyl- and triphenylphosphine complexes of the group 6 metal pentacarbonyls, M(CO)5PR3 (M = Cr, Mo, W and R = Me, Ph), have been measured using solid-state CP-MAS 31P NMR spectroscopy. For the trimethylphosphine derivatives, the chemical shift tensors have near axial symmetry and the shift tensor components are in reasonable agreement with the calculated values for the chromium and molybdenum complexes. In the triphenylphosphine complexes, the tensors are asymmetric due to the different torsion angles of the phenyl rings. The trend to higher shielding of the isotropic 31P chemical shifts on descending group 6 arises from changes in the perpendicular components of the shift tensor. The one-bond coupling constants, 1J(95/97Mo-31P), for the trimethyl- and triphenylphosphine complexes are 129 and 133 Hz, respectively.Key words: chemical shift anisotropy, phosphines, chromium, molybdenum, tungsten.

scholarly journals Oxygen-17 NMR spectroscopy of water molecules in solid hydrates

2016 ◽  
Vol 94 (3) ◽  
pp. 189-197 ◽  
Author(s):  
Sherif Nour ◽  
Cory M. Widdifield ◽  
Libor Kobera ◽  
Kevin M. N. Burgess ◽  
Dylan Errulat ◽  
...  
Keyword(s):  
Solid State ◽  
Chemical Shift ◽  
Density Functional ◽  
Chemical Shifts ◽  
Sodium Perchlorate ◽  
Coupling Constants ◽  
Water Molecules ◽  
Potassium Oxalate ◽  
Nmr Studies ◽  
Quadrupolar Coupling

17O solid-state NMR studies of waters of hydration in crystalline solids are presented. The 17O quadrupolar coupling and chemical shift (CS) tensors, and their relative orientations, are measured experimentally at room temperature for α-oxalic acid dihydrate, barium chlorate monohydrate, lithium sulfate monohydrate, potassium oxalate monohydrate, and sodium perchlorate monohydrate. The 17O quadrupolar coupling constants (CQ) range from 6.6 to 7.35 MHz and the isotropic chemical shifts range from –17 to 19.7 ppm. The oxygen CS tensor spans vary from 25 to 78 ppm. These represent the first complete CS and electric field gradient tensor measurements for water coordinated to metals in the solid state. Gauge-including projector-augmented wave density functional theory calculations overestimate the values of CQ, likely due to librational dynamics of the water molecules. Computed CS tensors only qualitatively match the experimental data. The lack of strong correlations between the experimental and computed data, and between these data and any single structural feature, is attributed to motion of the water molecules and to the relatively small overall range in the NMR parameters relative to their measurement precision. Nevertheless, the isotropic chemical shift, quadrupolar coupling constant, and CS tensor span clearly differentiate between the samples studied and establish a ‘fingerprint’ 17O spectral region for water coordinated to metals in solids.

13C NMR chemical shift calculations of charged surfactants in water — A combined density functional theory (DFT) and molecular dynamics (MD) methodological study

2013 ◽  
Vol 91 (7) ◽  
pp. 529-537 ◽  
Author(s):  
T. Mineva ◽  
Y. Tsoneva ◽  
R. Kevorkyants ◽  
A. Goursot
Keyword(s):  
Chemical Shift ◽  
Density Functional ◽  
Chemical Shifts ◽  
Water Solution ◽  
Basis Set ◽  
Conformational Sampling ◽  
Sodium Octanoate ◽  
Solvent Molecules ◽  
Isotropic Chemical Shifts ◽  
C Nmr

Structural and magnetic properties of one anionic and one cationic amphiphile molecule (sodium octanoate and hexadecyltrimethylammonium chloride, respectively) in water are studied comparing different methods to account for the presence of the solvent. Calculated 13C NMR chemical shifts are used as the probe for accuracy of the theoretical electronic structures obtained with different descriptions of the surfactants in water solution. The best agreement with the experimental data are obtained by averaging 13C NMR isotropic chemical shifts over a large number of conformational structures of sodium octanoate while considering the electronic structure of the solvent molecules. The 13C chemical shift values of the hexadecyltrimethylammonium alkane chain are systematically overestimated by 10–15 ppm even if an extensive conformational sampling and water as the polarized continuum medium have been taken into consideration. The role of the basis set quality has been studied and discussed as well.

scholarly journals Structure determination, vibrational bands and chemical shift assignments of 3-(4-(3-(2,5-dimethylphenyl)-3-methylcyclobutyl)thiazol-2-yl)-2-(o-tolyl)thiazolidin-4-one: A combined experimental and quantum chemical density-functional theory studies

2019 ◽  
Vol 38 (2) ◽  
pp. 183
Author(s):  
Fatih Şen
Keyword(s):  
Dft Calculations ◽  
Density Functional ◽  
Chemical Shifts ◽  
Molecular Geometry ◽  
Molecular Structures ◽  
Structural Bond ◽  
X Ray ◽  
X Ray Crystallography ◽  
13C Nuclear Magnetic Resonance ◽  
Experimental Findings

This paper report is an analysis of the title compound by means of X-ray crystallography, FT-IR, NMR and DFT calculations, in the context of structural and spectral characterization. The crystal and molecular structures of the compound were determined by single-crystal X-ray diffraction (SCXRD). Fourier Transform Infrared (FTIR) spectrum was recorded in the range from 400 cm–1 to 4000 cm–1. The 1H and 13C nuclear magnetic resonance (NMR) spectra were also recorded. DFT calculations were employed to support X-ray molecular geometry and calculate IR and NMR (1H and 13C) spectral bands. The structural (bond lengths, bond angles, torsion angles) and spectral (vibrational modes and chemical shifts) parameters obtained from DFT levels (B3LYP/6-31G(d,p) and B3LYP/6-31G+(d,p)) were compared with experimental findings, and an excellent harmony between the two data was ascertained.

Highly Electron-Deficient Pyridinium-Nitrones for Rapid and Tunable Inverse-Electron-Demand Strain-Promoted Alkyne-Nitrone Cycloaddition to Bicyclo[6.1.0]nonyne

2019 ◽  
Author(s):  
Praveen Gunawardene ◽  
Wilson Luo ◽  
Alexander M. Polgar ◽  
John F. Corrigan ◽  
Mark Workentin
Keyword(s):  
Density Functional Theory ◽  
Reaction Kinetics ◽  
Density Functional ◽  
Functional Theory ◽  
X Ray ◽  
Inverse Electron Demand ◽  
X Ray Crystallography ◽  
Electron Demand

<div> <div> <p>Highly accelerated inverse-electron-demand strain-promoted alkyne-nitrone cycloaddition (IED SPANC) between a sta- ble cyclooctyne (bicyclo[6.1.0]nonyne (BCN)) and nitrones delocalized into a Cα-pyridinium functionality is reported, with the most electron-deficient “pyridinium-nitrone” displaying among the most rapid cycloadditions to BCN that is currently reported. Density functional theory (DFT) and X-ray crystallography are explored to rationalize the effects of N- and Cα-substituent modifications at the nitrone on IED SPANC reaction kinetics and the overall rapid reactivity of pyridinium-delocalized nitrones.</p> </div> </div>

Sign in / Sign up

Export Citation Format

Share Document