title: Vibrational spectra, normal modes, ab initio and DFT calculations for 6-Chloro- and 7-Chloro-4-bromomethylcoumarins.
abstract: Vibration spectral measurements - Infrared (4000-400 cm(-1)) and Raman (3500-50 cm(-1)) spectra - have been made for the solid samples of 6-Chloro- and 7-Chloro-4-bromomethylcoumarins. Ground electronic state energies, equilibrium geometries, harmonic vibrational spectra and normal modes have been computed using ab initio - RHF/6-31G* - and DFT - B3LYP/6-31G* levels of theory. The optimization yielded three structures for each molecule, with one being a transition state structure. Of the remaining two conformers, one belongs to C(s) symmetry and the other belongs to C(1), the latter being the most stable one. The optimized dihedral angle for -CH(2)Br group is 111 degrees in agreement with X-ray diffraction results reported for the similar molecular systems. Assignment of all the observed spectral bands has been proposed. The absorptions show band pattern revealing isomer characteristics and vibrational coupling in varying degrees; the Raman spectra show structural changes associated with the rings as well as lattice modes.
authors.affiliation: Department of Physics, Karnatak University, Dharwad 580003, India. jtonannavar.kud.phys@gmail.com
authors.forename: J
authors.initials: J
authors.lastname: Tonannavar
authors.forename: Jayashree
authors.initials: J
authors.lastname: Yenagi
authors.forename: Veenasangeeta
authors.initials: V
authors.lastname: Sortur
authors.forename: V B
authors.initials: VB
authors.lastname: Jadhav
authors.forename: M V
authors.initials: MV
authors.lastname: Kulkarni
mesh_terms: D017606:Chlorine Compounds / Q000737:chemistry*; D003374:Coumarins / Q000737:chemistry*; D015394:Molecular Structure; D017550:Spectroscopy, Fourier Transform Infrared; D013059:Spectrum Analysis, Raman / Q000379:methods*; D014732:Vibration; D014961:X-Ray Diffraction
chemical_list: D017606:Chlorine Compounds; D003374:Coumarins