title: Infrared, Raman, and Ultraviolet Absorption Spectra and Theoretical Calculations and Structure of 2,3,5,6-Tetrafluoropyridine in its Ground and Excited Electronic States.
abstract: Infrared and Raman spectra of 2,3,5,6-tetrafluoropyridine (TFPy) were recorded and vibrational frequencies were assigned for its S0electronic ground states.Ab initioand density functional theory (DFT) calculations were used to complement the experimental work. The lowest electronic excited state of this molecule was investigated with ultraviolet absorption spectroscopy and theoretical CASSCF calculations. The band origin was found to be at 35,704.6 cm-1in the ultraviolet absorption spectrum. A slightly puckered structure with a barrier to planarity of 30 cm-1was predicted by CASSCF calculations for the S1(π,π*) state. Lower frequencies for the out-of-plane ring bending vibrations for the electronic excited state result from the weaker bonding within the pyridine ring.
authors.affiliation: Department of Chemistry, Texas A&M University, College Station, TX 77843-3255 USA.
authors.forename: Hong-Li
authors.initials: HL
authors.lastname: Sheu
authors.affiliation: Department of Chemistry, Texas A&M University, College Station, TX 77843-3255 USA.
authors.forename: Praveenkumar
authors.initials: P
authors.lastname: Boopalachandran
authors.affiliation: National Center for Biotechnology Information, National Library of Medicine, National Institutes of Health, Department of Health and Human Services, 8600 Rockville Pike, Bethesda, MD 20894, USA.
authors.forename: Sunghwan
authors.initials: S
authors.lastname: Kim
authors.affiliation: Department of Chemistry, Texas A&M University, College Station, TX 77843-3255 USA.
authors.forename: Jaan
authors.initials: J
authors.lastname: Laane
keywords: 2,3,5,6-tetrafluoropyridine; electronic excited state; molecular structure; ultraviolet absorption spectra; vibrational spectra