Calculated Versus “Experimental” Force Fields: The Influence in the Structure Determination of Benzene by NMR Spectroscopy in Liquid Crystal Solvents

Very accurate bond distances can be derived from dipolar couplings, D ij , obtained by analysis of the NMR spectra of samples dissolved in anisotropic solvents (LXNMR). To do this, however, the couplings must be corrected for the averaging produced by vibrational motion. The vibrational corrections require a knowledge of the force field, which may be obtained by fitting experimental vibrational frequencies or, much more easily, from quantum-mechanical computations. In the present study, the reliability of the methods used to calculate the force field and the effects on the accuracy of the vibrational corrections to the D ij is tested on benzene for which a very accurate structural study is available.

[1]  G. De Luca,et al.  Intrinsic information content of NMR dipolar couplings: a conformational investigation of 1,3-butadiene in a nematic phase. , 2006, Chemphyschem : a European journal of chemical physics and physical chemistry.

[2]  G. De Luca,et al.  Conformational analysis of 2,2'-bithiophene: a (1)H liquid crystal NMR study using the (13)C satellite spectra. , 2005, The journal of physical chemistry. A.

[3]  J. Emsley,et al.  The conformational distribution in diphenylmethane determined by nuclear magnetic resonance spectroscopy of a sample dissolved in a nematic liquid crystalline solvent , 2003 .

[4]  M. Morsy,et al.  Normal Vibrational Mode Analysis and Assignment of Benzimidazole by ab Initio and Density Functional Calculations and Polarized Infrared and Raman Spectroscopy , 2002 .

[5]  D. C. Mckean,et al.  Vibrational and quantum chemical studies of 1,2-difluoroethylenes: Spectra of 1,2-13C2H2F2 species, scaled force fields, and dipole derivatives , 2002 .

[6]  H. Takeuchi,et al.  Molecular structure of N-methylpyrrole studied by gas electron diffraction using rotational constants and liquid–crystal NMR spectroscopy , 2001 .

[7]  S. Katsyuba,et al.  Vibrational spectra and conformational isomerism of calixarene building blocks. Part I. Diphenylmethane, (C 6 H 5 ) 2 CH 2 , 2001 .

[8]  J. Jokisaari,et al.  Characterisation of the structure, deuterium quadrupolar tensors, and orientational order of acenaphthene, a rigid, prochiral molecule, from the NMR spectra of samples dissolved in nematic and chiral nematic liquid crystalline solvents , 2001 .

[9]  T. Rantala,et al.  Calculation of the Molecular Ordering Parameters of (±)-3-Butyn-2-ol Dissolved in an Organic Solution of Poly(γ-benzyl-l-glutamate) , 1997 .

[10]  Leo Radom,et al.  Harmonic Vibrational Frequencies: An Evaluation of Hartree−Fock, Møller−Plesset, Quadratic Configuration Interaction, Density Functional Theory, and Semiempirical Scale Factors , 1996 .

[11]  Ming Wah Wong,et al.  Vibrational frequency prediction using density functional theory , 1996 .

[12]  Emilia Sicilia,et al.  Graphical Interactive Strategy for the Analysis of NMR Spectra in Liquid Crystalline Phases , 1994, J. Chem. Inf. Comput. Sci..

[13]  P. Diehl,et al.  Proton NMR study of partially oriented benzene and chlorobenzene: Determination of the rα structure and of bond contributions to the orientation , 1989 .

[14]  P. Diehl,et al.  The effects of the correlation between vibration and rotation of partially oriented molecules on the N.M.R. parameters , 1984 .

[15]  P. Diehl,et al.  A general theory for the correlation between vibration and rotation of partially oriented molecules and for its effects on the NMR parameters , 1984 .

[16]  P. Diehl,et al.  Vibrational corrections in NMR spectra of oriented molecules , 1979 .

[17]  P. Diehl,et al.  The rα structure of [1-13C]benzene by NMR of oriented molecules: A study of the possible precision and of solvent effects , 1979 .

[18]  J. Scherer.  A transferable force-field for out-of-plane vibrations of chlorinated benzenes , 1967 .

[19]  J. Scherer.  A comparison of Urey Bradley and valence force-fields for chlorinated benzenes , 1964 .