Infrared, Raman, and Ultraviolet Absorption Spectra and Theoretical Calculations and Structure of
Hong-Li Sheu1, Praveenkumar Boopalachandran1, Sunghwan Kim2
1Department of Chemistry, Texas A&M University, College Station, TX 77843-3255 USA.
Abstract:
Infrared and Raman spectra of 2,3,5,6-tetrafluoropyridine (TFPy) were recorded and vibrational frequencies were assigned for its S0 electronic ground states. Ab initio and 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-1 in the ultraviolet absorption spectrum. A slightly puckered structure with a barrier to planarity of 30 cm-1 was 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.
Related Concept Videos
Raman Spectroscopy: Overview
However, a small fraction of the scattered light exhibits a frequency shift due to the exchange of energy between the incident photons and...
UV–Vis Spectroscopy: Molecular Electronic Transitions
Infrared (IR) Spectroscopy: Overview
Different compounds display unique properties due to their...
IR Spectroscopy: Molecular Vibration Overview
Stretching vibrations are vibrational motions that occur along the bond line, changing the bond length or distance between two bonded atoms. They are further distinguished as symmetric or asymmetric. In symmetric stretching, the...
Variables Affecting Phosphorescence and Fluorescence
Molecular Spectroscopy: Absorption and Emission


