title: Vibrational spectra of the ortho-nitroanilinium cation in torsional space. Theoretical studies vs. experimental data of ortho-nitroanilinium chloride.
abstract: Crystal structure of the ortho-nitroanilinium chloride, (HoNA)Cl, was re-determined by means of X-ray single crystal diffraction. Hydrogen atoms of the ammonio form intra- and intermolecular hydrogen bonds which are arranged in chain and ring patterns. The patterns are described by the mathematical relations of the elementary graph-set descriptors. Since the interactions have a weak nature, the interpretation of the vibrational spectra was carried out with the help of theoretical calculations of the spectra for the HoNA+ ion. In order to properly assign experimental bands, theoretical spectra were calculated at the B3LYP/6-31G(d,p) level of theory for the geometry of global minimum of HoNA+ ion as a reference and for the other conformations, including in-crystal geometry of the ion, changing the relative position of the ammonio and nitro groups. Overall, the 89 spectra were analyzed as a two-dimensional dependence of each of 45 normal modes of the HoNA+ ion on two dihedral angles, dih(HNCC) and dih(ONCC). Additionally, calculations were done for the in-crystal conformation of the (HoNA)Cl3(2-) anion. Great increase of frequency is observed for the ν7 (641 cm(-1)), where the H1C atom is involved in, because the intramolecular N-H1C⋯O hydrogen bond weakens upon rotation of the NH3+ group. PED analysis shows that also the modes of vibrations changes upon rotation. The mode of vibrations for the (HoNA)Cl3(2-) anion differs from the HoNA+ ion, especially for the ν(N-H) vibrations. Besides, when three chloride anions where included in the calculations, only then the experimental spectra were well reproduced.
authors: Institute of Low Temperature and Structure Research, Polish Academy of Sciences, Okólna str. 2, P.O. Box 1410, 50-950 Wrocław, Poland. Electronic address: m.daszkiewicz@int.pan.wroc.pl.
authors: Marek
authors: M
authors: Daszkiewicz
mesh_terms: D002412:Cations; D018360:Crystallography, X-Ray; D006860:Hydrogen Bonding; D008958:Models, Molecular; D008968:Molecular Conformation; D009574:Nitro Compounds / Q000737:chemistry*; D000644:Quaternary Ammonium Compounds / Q000737:chemistry*; D017550:Spectroscopy, Fourier Transform Infrared; D013059:Spectrum Analysis, Raman; D013696:Temperature; D054159:Torsion, Mechanical; D014732:Vibration
chemical_list: D002412:Cations; D009574:Nitro Compounds; D000644:Quaternary Ammonium Compounds
keywords: DFT; Elementary graph-set descriptor; Ortho-nitroaniline; Vibrational spectra