title: Computation and interpretation of vibrational spectra on the structure of Losartan using ab initio and Density Functional methods.
abstract: The solid phase FTIR and FT-Raman spectra of Losartan have been recorded in the region 400-4000 cm(-1). The spectra were interpreted in terms of fundamental modes, combination and overtone bands. The structure of the molecule was optimized and the structural characteristics were determined by Quantum chemical methods. The vibrational frequencies yield good agreement between observed and calculated values. The infrared and Raman spectra were also predicted from the calculated intensities. 1H and 13C NMR spectra were recorded and resonance chemical shifts of the molecule were calculated. UV-Visible spectrum of the compound was recorded in the region 200-600 nm and the electronic properties HOMO and LUMO energies calculated by TD-HF approach. NBO atomic charges of the molecules and second order perturbation theory analysis of Fock matrix also calculated and interpreted. The geometrical parameters, energies, harmonic vibrational frequencies, IR intensities, Raman intensities, and absorption wavelengths were compared with experimental and theoretical data of the molecule.
authors.affiliation: Department of Physics, Dr. M.G.R. Educational & Research Institute University, Chennai 600095, TN, India; Department of Physics, SCSVMV University, Enathur, Kanchipuram 631561, TN, India.
authors.forename: B
authors.initials: B
authors.lastname: Latha
authors.affiliation: Research and Development, St. Peter's Institute of Higher Education and Research, St. Peter's University, Avadi, Chennai 600054, TN, India.
authors.forename: S
authors.initials: S
authors.lastname: Gunasekaran
authors.affiliation: PG and Research Department of Physics, Presidency College, Chennai 600005, TN, India.
authors.forename: S
authors.initials: S
authors.lastname: Srinivasan
authors.affiliation: Department of Physics, C. Kandaswami Naidu College for Men in Anna Nagar East, Chennai 600102, TN, India. Electronic address: gr.ramkumaar@yahoo.com.
authors.forename: G R
authors.initials: GR
authors.lastname: Ramkumaar
mesh_terms: D066241:Carbon-13 Magnetic Resonance Spectroscopy; D004583:Electrons; D019808:Losartan / Q000737:chemistry*; D008958:Models, Molecular; D008968:Molecular Conformation; D066244:Proton Magnetic Resonance Spectroscopy; D011789:Quantum Theory; D013056:Spectrophotometry, Ultraviolet; D017550:Spectroscopy, Fourier Transform Infrared; D013059:Spectrum Analysis, Raman; D013816:Thermodynamics; D014732:Vibration
chemical_list: D019808:Losartan
keywords: FT-IR; Hyperpolarizability; Losartan; NBO; UV–Visible