Effect of Intermolecular Hydrogen Bonding on the Nuclear Quadrupole Interaction in Imidazole and its Derivatives as Studied by ab initio Molecular Orbital Calculations

Abstract

Ab initio Hartree-Fock molecular orbital calculations were applied to the crystalline imidazole and its derivatives in order to examine systematically the effect of possible N-H---N type hydrogen bonding on the nuclear quadrupole interaction parameters in these materials. The nitrogen quadrupole coupling constant (QCC) and the asymmetry parameter (r?) of the electric field gradient (EFG) were found to depend strongly on the size of the molecular clusters, from single molecule, to dimer, trimer and to the infinite molecular chain, i.e., crystalline state, implying that the intermolecular N-H -N hydrogen bond affects significantly the electronic structure of imidazole molecule. A certain correlation between the QCC of l4 N and the N-H bond distance R was also found and interpreted on the basis of the molecular orbital theory. However, we found that the value of the calculated EFG at the hydrogen position of the N-H group, or the corresponding QCC value of 2 H, increases drastically as /C* when R is shorter than about 0.1 nm, due probably to the inapplicability of the Gaussian basis sets to the very short chemical bond as revealed in the actual imidazole derivatives. We suggested that the observed N-H distances in imidazole derivatives should be re-examined.

Influence of hydrogen bond geometry on quadrupole coupling parameters: A theoretical study of imidazole–water and imidazole–semiquinone complexes

“…In contrast, the N1 parameters are considerably affected by hydrogen bonding, the value of Z increases and the value of w decreases. These trends were also found before in experimental 41,44 or theoretical 7,14,43 studies of systems involving imidazole derivatives. The hydrogen bond geometry of this equilibrium structure can be described by r(O-N) eq ¼ 2.97 A ˚, Taking the equilibrium structure as a starting point, the inplane angle a is defined as a ¼ 125.81 À +(C2-N1-O) and the out-of-plane angle b as the angle between the O-N vector and the C2-C5-N1 plane (see Fig.…”

“…Previous theoretical studies have pointed out the importance of intermolecular hydrogen bonding in imidazole crystals for a correct computation of the NQR values. 7,14,43 The good agreement between gas-phase experimental data and the calculated QC parameters demonstrates that the applied level of theory may also yield quantitatively reliable values.…”

“…This and other rearrangements in the direct bonding environment of the imidazole nitrogen atom will have a large influence on its QC parameters. For the resulting structures the 14 N EFG tensors and the w and Z values were calculated as a function of r, a or b.…”

“…However, these systems represent a different type of hydrogen bonding than the imidazole-water and methylimidazole-benzosemiquinone models or do not involve hydrogen bonding at all. In the present work a systematic investigation of the influence of hydrogen bond geometry on imidazole 14 N QC parameters is presented. The effects of hydrogen bond length variation and of in-and out-of-plane distortions of the bonding geometry as well as a twist of bonding partners with respect to each other are discussed and the magnitude and direction of the corresponding QC tensor changes are pointed out.…”

A DFT study of the 67Zn, 14N and 2H electric field gradient tensors in Zinc(II)–4-MeIm complexes and extrapolation to superoxide dismutase

“…Fritscher studied the influence of hydrogen bond geometry on 14 N quadrupole interactions in imidazole-water and methyl imidazole-benzosemiquinone systems [24]. In another work in this area, the 14 N and 2 H quadrupole interaction parameters in a variety of substituted imidazoles were used to determine the crystal structure and to confirm the existence of intermolecular hydrogen bonding [25][26][27]. In addition, Morokuma et al investigated the 14 N NQR parameters of a series of imidazole derivatives in different environments in both the gas phase and the solid state [28].…”