Structural and vibrational study of 2‐(2′‐ furyl)‐4,5‐1H‐dihydroimidazole

Abstract

In this study 2-(2(-furyl)-4,5-1H-dihydroimidazole (1) was prepared and then characterized by infrared, Raman, and multidimensional nuclear magnetic resonance (NMR) spectroscopies. The crystal and molecular structures of 1 were determined by X-ray diffraction methods. The density functional theory (DFT) and second-order Møller-Plesset theory (MP2) with Pople's basis set show that there are two conformers for the title molecule that have been theoretically determined in the gas phase, and that only one of them, conformer I, is present in the solid phase. NMR spectra observed for 1 were successfully compared with the calculated chemical shifts at the B3LYP/6-311RRG ** level theorized for this conformer. The harmonic vibrational frequencies for the optimized geometry of the latter conformer were calculated at the B3LYP/6-311RRG ** level in the approximation of the isolated molecule. For a complete assignment of the IR and Raman spectra in the solid phase of 1, DFT calculations were combined with Pulaý s scaled quantum mechanics force field (SQMFF) methodology to fit the theoretical frequency values to the experimental ones.

Structural and vibrational analyses of 2‐(2‐benzofuranyl)‐2‐imidazoline

“…The inclusion of polarization functions is important to have a better agreement with the experimental geometry. In general, our values are in agreement with the experimental ones for the corresponding imidazoline ring of 2-(2 -furyl)-4,5-1H-dihydroimidazole, [21] but for the furane ring there is a significant difference between those values. The calculated C12-O11 bond lengths for both BFI conformers are very different from the observed C-O distance in 2-(2 -furyl)-4,5-1H-dihydroimidazole [21] because of the presence of the benzyl and CH 2 groups in the furane ring of BFI.…”

“…In general, our values are in agreement with the experimental ones for the corresponding imidazoline ring of 2-(2 -furyl)-4,5-1H-dihydroimidazole, [21] but for the furane ring there is a significant difference between those values. The calculated C12-O11 bond lengths for both BFI conformers are very different from the observed C-O distance in 2-(2 -furyl)-4,5-1H-dihydroimidazole [21] because of the presence of the benzyl and CH 2 groups in the furane ring of BFI. Furthermore, the theoretical calculations by using the 6-311++G * * basis set also predict that the two rings in both BFI conformers are not coplanar, with values of ∠C14-C10-C2 between 112 and 114 • , whereas in 2-(2 -furyl)-4,5-1H-dihydroimidazole [21] this angle has a value of 132.73 • .…”

“…Table 1 shows a comparison of the calculated geometrical parameters for both BFI conformers with those observed from X-ray diffraction corresponding to 2-(2 -furyl)-4,5-1H-dihydroimidazole. [21] The theoretical values corresponding to the furane and imidazoline rings for both conformers were compared with the corresponding experimental values of the above-mentioned compound. According to these results, the basis set that best reproduces the experimental geometrical parameters for BFI is 6-311++G * * for bond lengths and angles, where the mean difference is 0.027 Å for the anti and syn conformers, whereas using 6-31G * basis set, the difference in bond lengths between the conformers is 0.002 Å.…”

Vibrational Study and Force Field of the Citric Acid Dimer Based on the SQM Methodology

“…The SQM force fields for the compound dimer can be obtained at request. The broad band observed between 3400 and 2200 cm −1 in the experimental IR spectra of the compound in the solid phase can be attributed to the O-H hydrogen bond formed by the spatial arrangement of molecules in the lattice crystal [41,42]. Note that the theoretical infrared spectra for the monomer structure demonstrate a little agreement with the experimental spectrum (Figure 2), especially in the high wavenumbers cm −1 region.…”

Structural and Vibrational Properties and NMR Characterization of (2’-furyl)-Imidazole Compounds

“…Recently, the theoretical and experimental studies on structure, electronic and vibrational properties for the (2'-furyl)-imidazole series were reported by us 13,14,15,16,17 .…”