In search of OH–π interactions between 1-methylimidazole and water using a combined computational quantum chemistry and ATR-FTIR spectroscopy approach (original) (raw)
Related papers
Journal of Molecular Structure, 2009
Synthesis of two new 1-(2-methylpropenyl)-2-methylbenzimidazoles by reaction of 2-methylbenzimidazole with 3-chloro-2-methylpropene using a strong base as a catalyst is described. Gas chromatographymass spectrometry (GC-MS) allowed the characterization of the structural isomers: the slightly more stable 1-(2-methyl-1-propenyl)-2-methylbenzimidazole (51%) and a less stable 1-(2-methyl-2-propenyl)-2-methylbenzimidazole (49%). The results of theoretical calculations indicate that the difference in the energy between the two structural isomers is 3.21 kcal mol À1 at the B3LYP/6-311+G ** level. The structures were confirmed by 1 H and 13 C Nuclear Magnetic Resonance, elemental analysis and spectroscopic methods such as FT-Raman, FT-IR and UV-VIS. The experimental results were supported by performing DFT calculations for energies, geometries, vibrational frequencies and shieldings constants using 6-311+G ** basis sets and B3LYP functional. The theoretical data have satisfactorily reproduced the experimental results. The consistency and efficiency of the GIAO method used to calculate absolute shielding of the studied compounds were checked by the analysis of statistical parameters and were found to be in excellent agreement with experimental values. This correlation has been used for unambiguous NMR signal assignments for studied compounds.
Journal of Molecular Structure, 2010
Benzimidazole and its derivatives are accepted pharmacophores and represent important synthetic precursors in new drugs discovery. These heterocyclic compounds have awakened great interest during the last few years because of their proven biological activity as antiviral, antimicrobial and antitumoral agents. In this chapter, we report a combined experimental and theoretical study on the molecular structures and vibrational spectra of five new 1-derivatives of 2-methylbenzimidazole, including its isomers. The structures of the target compounds were confirmed by 1 H and 13 C NMR, elemental analysis, mass spectrometry and spectroscopic methods such as Raman, FT-IR, and UV-VIS. The experimental results were supported by performing density functional theory (DFT) calculations for energies, geometries, vibrational frequencies and NMR shielding constants using 6-311+G** basis sets and B3LYP functional. The theoretical data, using DFT approximation, and experimental results were consistent with each other.
Chemical Physics Letters, 2013
The Letter demonstrates an experimental and computational investigation of intermolecular interactions in binary system of 1-methylimidazole (MeIm) with methanol. The densities of binary system were measured at T = 288.15-323.15 K, and the values of excess molar volumes were obtained as a function of composition at each temperature. The experimental results indicate the formation of strong cross-associated complex in the binary system. Meanwhile, the nature of hydrogen bond of the associated complexes was explored based on theoretical calculations. In addition, the changes of thermodynamic properties from the monomers to cross-associated complex were also investigated.
Chemical Physics, 2004
Density functional theory (DFT) has gained much popularity over the last decades, due to its computational efficiency as compared to other correlated electronic structure methods. It is generally found that the accuracy of DFT rivals that of MP2 for conventional hydrogenbonded systems . However, probably the most significant deficiency of current density functionals is their inability to correctly account for the dispersion interaction . The reason for this is that both local density approximation (LDA) and generalized gradient approximation (GGA) functionals, and consequently also hybrid functionals (in which a fraction of the exact Hartree-Fock exchange energy is mixed into the exchange functional) are essentially local and therefore do not directly account for the electron density on a second, remote atom (as explained in more detail in ). This implies that state-of-the-art DFT is not suitable for systems containing dispersion-dominated interactions. Thus, current DFT functionals cannot be employed to describe the interaction of the rare-gas dimers: DFT yields He 2 interaction energies ranging from 1 to 120 K, depending on the particular density functional employed, whereas the exact result is 11 K [4]. Other dispersion-rich interactions include base-stacking interactions, water molecules interacting with aromatic rings; and indeed, all interactions involving p electron clouds.
Cation binding effect on hydrogen bonded dimer of imidazole and water
Inorganica Chimica Acta, 1987
The influence of small monovalent cations on neighbouring hydrogen bonds is studied for imidazole-water adducts by means of ab initio calculations using minimal Gaussian basis sets. Metal binding is found to have a significant effect on both hydrogen bond energy and the equilibrium intermolecular distance. A redistribution of electron density in the complex is also indicated by Muliiken population analysis. The net stabilization of the Hbond due to Li(I) ion is-8.9 kcal mol-', the N-H......
The Journal of Physical Chemistry A
The effect of the solvent on the ground state free energy differences of three enol conformers of 2-(2′hydroxyphenyl)benzimidazole and its keto tautomer has been examined by means of Monte Carlo simulations and continuum model calculations. In agreement with the experimental data, calculations show that the trans enol and keto forms are stabilized by polar solvents, leading to a conformational and tautomeric equilibrium with the closed cis enol conformer in water, the only single species in apolar solvents. Monte Carlo simulations have also been used to examine the influence of the solvent on the absorption band of the closed cis enol structure and the fluorescence band of the keto form generated by photoinduced intramolecular proton transfer. In concordance with the experimental spectra, absorption and fluorescence band maxima for the closed cis enol and keto forms, respectively, are found to be blue-shifted with increasing polarity and hydrogen bonding capacity of the solvent.
Chemical Physics Letters, 2004
Nuclear quadrupole resonance (NQR) parameters of 14 N, 2 H of N 2 H groups are calculated for imidazole and 4-nitroimidazole using HF and B3LYP methods. These computations are performed on the basis of X-ray and neutron diffraction structural data which are collected at 100, 103, 123 and 293 K temperatures. In order to take into account intermolecular hydrogen bonds and the van der Waals effects, two different sizes of clusters have been considered. Results of calculation have been compared with that of a single molecule in each case. Calculations illustrate that for imidazole and 4-nitroimidazole octameric and trimeric clusters, respectively, suffice to generate results which are compatible with experimental data. Our calculated NQR parameters and X-ray data show no significant structural change for 4-nitroimidazole at 293 and 100 K.
Journal of Physical Chemistry A, 2002
Molecular structure and fundamental vibrational frequencies of benzimidazole (BZI) are reported using ab initio-Hartree-Fock (HF) and density functional theory (DFT) methods at different levels of calculation. Observed polarized IR and Raman fundamentals of polycrystalline, single crystal, KBr-BZI disks, and gaslike samples are analyzed and assigned by comparison to the computed values. The assignment of fundamentals shows a one-to-one correspondence between the observed and calculated fundamentals using the BLYP/6-31G* level of calculation without applying any scaling factor except for XH stretching (X represents C or N), where a 0.995 scaling factor has been used. Hydrogen bonding and its effects on some normal vibrational modes are discussed. The results show that the nonscaled BLYP/6-31G* level of calculation may be used as a reference for assessing the intermolecular hydrogen bonding effect.