Search results for "MR Spectroscopy"

Karplus-Type Dependence of Vicinal119Sn-13C and119Sn-1H Spin-Spin Couplings in Organotin(IV) Derivatives: A DFT Study

2009

The empirical Karplus-type dependence of (3)J((119)Sn,(13)C) and (3)J((119)Sn,(1)H) couplings in organotin(IV) derivatives has been computationally validated by DFT methods both at the nonrelativistic and scalar ZORA relativistic level. A preliminary calibration of the computational protocols, by comparing experimental and calculated couplings for a Set Of Suitable rigid molecules, revealed their high predictive power: in particular, relativistic results for (3)J((119)Sn,(13)C) have a mean absolute error of just above 2 Hz, over a range of values up to about 70 Hz. The latter protocol has then been used to study in detail the influence of substituents and multiple paths connecting the coupl…

"Through-space" nuclear spin-spin J(PP) coupling in tetraphosphine ferrocenyl derivatives: a (31)P NMR and X-ray structure correlation study for coor…

2004

Herein, we report on (31)P(31)P solution-phase "through-space" nuclear spin-spin coupling constants (J(PP)) from a novel family of organometallic tetraphosphine nickel and palladium complexes. These J(PP) constants were accurately determined through NMR iterative simulation based on the second-order spectra obtained for the compounds. The corresponding solid-state X-ray structures of the complexes were determined, and the "through-space" P.P distances are reported. Due to the blocked conformation of the species in solution, a qualitative and semiquantitative experimental correlation is obtained, which links the geometric parameters and the intensity of the corresponding P.P coupling constan…

“Through-space” nuclear spin–spin couplings in ferrocenyl polyphosphanes and diphosphino cavitands: A new way of gathering structural information in …

2009

Abstract Nuclear magnetic resonance is an invaluable technique for investigating a variety of important issues ranging from the determination of molecular structure to therapeutic medical imaging. In this respect, the indirect nuclear spin–spin coupling involving common nuclei such as 1 H, 13 C or 31 P provides, via the J constant, conclusive data for compound characterization in solution. This electron-mediated nuclear spin coupling is usually regarded as being transmitted by covalently bonded magnetic atoms. However, several experimental and theoretical studies, first focused on constrained organofluorides, and more recently devoted to phosphane ligands highlighted the existence of very i…

Relativistic DFT Calculation of (119)Sn Chemical Shifts and Coupling Constants in Tin Compounds.

2006

The nuclear shielding and spin-spin coupling constants of (119)Sn in stannane, tetramethylstannane, methyltin halides Me4-nSnXn (X = Cl, Br, I; n = 1-3), tin halides, and some stannyl cations have been investigated computationally by DFT methods and Slater all-electron basis sets, including relativistic effects by means of the zeroth order regular approximation (ZORA) method up to spin-orbit coupling. Calculated (119)Sn chemical shifts generally correlate well with experimental values, except when several heavy halogen atoms, especially iodine, are bound to tin. In such cases, calculated chemical shifts are almost constant at the scalar (spin-free) ZORA level; only at the spin-orbit level i…

A DFT study of the vicinal 3J(119Sn,13C) and 3J(119Sn,1H) coupling constants in trimethyl- and chlorodimethyl-stannyl propanoates.

2013

Abstract We have tested the performance of DFT protocols, both at the Scalar relativistic ZORA and non-relativistic level of theory, for the calculation of the 3 J( 119 Sn, 13 C) and 3 J( 119 Sn, 1 H) vicinal couplings for a series of flexible organotin(IV) derivatives with formula XMe2SnCHRCHR′COOMe (X = Me, Cl; R, R′ = Me, Ph). A satisfactory agreement between experimental and calculated vicinal couplings has been obtained by taking into account the conformational behaviour of the compounds investigated. The protocols used, mainly the relativistic one, were found to give a correct picture of the populations and a sufficiently high overall performance in calculating the vicinal couplings, …

Additional Proof for the Structure of the New Flavone Galangustin (Bucegin) Obtained by 13C-NMR Spectroscopy

2010

3-(4-Fluorophenyl)-1-methyl-4-(4-pyridyl)quinolin-2(1H)-one

2007

The title compound, C21H15FN2O, was synthesized in the course of our studies of p38 mitogen-activated protein kinase inhibitors. It has been investigated by 1H and 13C NMR spectroscopy and was proven by X-ray crystallographic analysis to be the N-methyl rather than the O-methyl isomer. In the crystal structure, a three-dimensional network is formed consisting of quinolinone aromatic stacking inter­actions and weak C—H⋯O and C—H⋯N hydrogen bonds.

Tetranitroresorcin[4]arene: synthesis and structure of a new stereoisomer

2009

The direct reaction between 2-nitroresorcinol and acetaldehyde in alkaline medium yields tetranitro-C1-resorcin[4]arene in a moderate 8.2% overall yield which was characterized by single crystal X-ray crystallography, 1H NMR spectroscopy and electrospray ionization mass spectrometry (ESI-MS). In solution and in the solid state, the product adopts a unique, thermally stable and unprecedented rcct-boat conformation.

Complete assignments of1H and13C NMR spectra of four hispanane diterpenoids

2000

An NMR study of four hispanane diterpenoids is described. In addition to conventional 1D NMR methods, 2D shift-correlated experiments [1H,1H-COSY, 1H,1H-TOCSY, 1H,13C-HSQC-1J(C,H). 1H,13C-HMBC-nJ(C,H) (n = 2 and 3)] and 2D 1H,1H-NOESY were used for the complete and unambiguous 1H and 13C chemical shift assignments of these diterpenoids. Copyright © 2000 John Wiley & Sons, Ltd.

Preparation and structural studies on diorganotin(IV) complexes of N-nitroso-N-phenylhydroxylaminates

2007

Abstract Diorganotin(IV)-complexes of the N -nitroso- N -phenylhydroxylaminates (hereinafter cupf), Et 2 Sn(cupf) 2 ( 1 ), Bu 2 Sn(cupf) 2 ( 2 ), {[Bu 2 Sn(cupf)] 2 O} 2 ( 3 ), t -Bu 2 Sn(cupf) 2 ( 4 ) and Oc 2 Sn(cupf) 2 ( 5 , 6 ) were prepared and characterised by FT-IR and Mossbauer spectroscopic measurements. The binding modes of the ligand were identified by FT-IR spectroscopy, and it was found that the ligand is coordinated in chelating or bridging mode to the organotin(IV) center. The 119 Sn Mossbauer and FT-IR studies support the formation of trans -O h ( 1 – 6 ) structures. The X-ray diffraction analysis of 4 revealed that the tin centre is in a skew-trapezoidal geometry defined by…