Structural and Vibrational Study of 2-(2’- furyl)-1H-imidazole

A. E. LEDESMA; S. A. BRANDAN; J. ZINCZUK; O. E. PIRO; J. J. LÓPEZ GONZÁLEZ; A. BEN ALTABEF

Journal Physical Organic Chemistry

Wiley

Año: 2008 vol. 21 p. 1086 - 1097

The 2-(2(-furyl)-1H-imidazole (1) has been prepared and characterized using infrared, Raman, and multidimensional nuclear magnetic resonance spectroscopies. Two conformations of this species obtained by rotation of 1808, approximately, around the C—C inter-ring bond are detected. Likewise, the crystal and molecular structure of 1 has been analyzed by X-ray diffraction methods and it evidenced that both conformations are present in the lattice with equal occupancy and linked in alternate way to the N—H---N bonded polymeric chains along the crystal [101] direction. Theoretical calculations have been carried out by employing the density functional theory (DFT)/B3LYP method, in order to optimize the geometry in gas phase of both conformers and to support the assignments of the vibrational bands of 1 to their normal modes. For a complete assignment of the compound, DFT calculations were combined with Pulay’s SQMFF methodology in order to fit the theoretical frequency values to the experimental one. The nuclear magnetic resonance spectrum observed for 1 is successfully compared with the calculated chemicals shifts at B3LYP/6-311þþG** level of theory for the two conformers. Furthermore, natural bond orbital (NBO) analysis and topological (AIM) calculations for an oligomer, containing three alternated units of the N—H---N bonded chain found in the crystal, reveals the characteristics of the hydrogen bonds present in the polymeric structure.