title: Quantum chemical study on influence of intermolecular hydrogen bonding on the geometry, the atomic charges and the vibrational dynamics of 2,6-dichlorobenzonitrile.
abstract: FT-IR (4000-400 cm(-1)) and FT-Raman (4000-200 cm(-1)) spectral measurements on solid 2,6-dichlorobenzonitrile (2,6-DCBN) have been done. The molecular geometry, harmonic vibrational frequencies and bonding features in the ground state have been calculated by density functional theory at the B3LYP/6-311++G (d,p) level. A comparison between the calculated and the experimental results covering the molecular structure has been made. The assignments of the fundamental vibrational modes have been done on the basis of the potential energy distribution (PED). To investigate the influence of intermolecular hydrogen bonding on the geometry, the charge distribution and the vibrational spectrum of 2,6-DCBN; calculations have been done for the monomer as well as the tetramer. The intermolecular interaction energies corrected for basis set superposition error (BSSE) have been calculated using counterpoise method. Based on these results, the correlations between the vibrational modes and the structure of the tetramer have been discussed. Molecular electrostatic potential (MEP) contour map has been plotted in order to predict how different geometries could interact. The Natural Bond Orbital (NBO) analysis has been done for the chemical interpretation of hyperconjugative interactions and electron density transfer between occupied (bonding or lone pair) orbitals to unoccupied (antibonding or Rydberg) orbitals. UV spectrum was measured in methanol solution. The energies and oscillator strengths were calculated by Time Dependent Density Functional Theory (TD-DFT) and matched to the experimental findings. TD-DFT method has also been used for theoretically studying the hydrogen bonding dynamics by monitoring the spectral shifts of some characteristic vibrational modes involved in the formation of hydrogen bonds in the ground and the first excited state. The (13)C nuclear magnetic resonance (NMR) chemical shifts of the molecule were calculated by the Gauge independent atomic orbital (GIAO) method and compared with experimental results. Standard thermodynamic functions have been obtained and changes in thermodynamic properties on going from monomer to tetramer have been presented.
authors.affiliation: Department of Physics, Lucknow University, Lucknow, India.
authors.forename: Parag
authors.initials: P
authors.lastname: Agarwal
authors.affiliation: Department of Applied Physics, Faculty of Engineering & Technology, M.J.P. Rohilkhand University, Bareilly, India.
authors.forename: Saba
authors.initials: S
authors.lastname: Bee
authors.affiliation: Department of Applied Physics, Faculty of Engineering & Technology, M.J.P. Rohilkhand University, Bareilly, India. Electronic address: drarchana.physics@gmail.com.
authors.forename: Archana
authors.initials: A
authors.lastname: Gupta
authors.affiliation: Department of Physics, Lucknow University, Lucknow, India.
authors.forename: Poonam
authors.initials: P
authors.lastname: Tandon
authors.affiliation: Aryan Institute of Technology, Ghaziabad, India.
authors.forename: V K
authors.initials: VK
authors.lastname: Rastogi
authors.affiliation: Department of Inorganic and Physical Chemistry, Indian Institute of Science, Bangalore, India.
authors.forename: Soni
authors.initials: S
authors.lastname: Mishra
authors.affiliation: Department of Chemistry, Lucknow University, Lucknow, India.
authors.forename: Poonam
authors.initials: P
authors.lastname: Rawat
mesh_terms: D002152:Calorimetry, Differential Scanning; D006860:Hydrogen Bonding; D009682:Magnetic Resonance Spectroscopy; D000432:Methanol / Q000737:chemistry; D008958:Models, Molecular; D008968:Molecular Conformation; D009570:Nitriles / Q000737:chemistry*; D011789:Quantum Theory; D012996:Solutions; D013056:Spectrophotometry, Ultraviolet; D017550:Spectroscopy, Fourier Transform Infrared; D013059:Spectrum Analysis, Raman; D055672:Static Electricity; D013816:Thermodynamics; D014732:Vibration
chemical_list: D009570:Nitriles; D012996:Solutions; C055869:dichlobanil; D000432:Methanol
keywords: BSSE; DFT; Excited state dynamics; Intermolecular interactions; Vibrational spectroscopy