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Abstract
Pentafluoropyridine (PFP) undergoes fast structural isomerisation to fulvenes when irradiated with 9R(16) CO2 laser line in the fluence range 0.5–1.5 J/cm2. The unstable fulvenes slowly decay back to PFP in ms time scale. No detectable permanent dissociation of PFP was observed in the above low fluence experiments. However, by using focused CO2 laser beam for the irradiation of PFP, an emission of light in the visible/near‐UV was observed. The time evolution of the luminescence reveals three peaks at 390, 460 and 500 nm on a broad background emission of 300–680 nm. These bands are assigned to the fluorescence of PFP via inverse electronic relaxation (IER) and C2 Swan bands. On prolonged irradiation of PFP in focused condition a small extent of permanent dissociation was observed with the major products as C2F4, a sooty yellow deposit and another compound presumed to be Dewar PFP.
Highlights
Pentafluoropyridine (PFP) undergoes fast structural isomerisation to fulvenes when irradiated with 9R(16) CO2 laser line in the fluence range 0.5-1.5 J/cm[2]
The time evolution of the luminescence reveals three peaks at 390, 460 and 500 nm on a broad background emission of 300-680 nm. These bands are assigned to the fluorescence of PFP via inverse electronic relaxation (IER) and C2 Swan bands
The time resolved studies in UV flash photolysis of benzene have indicated that internal conversion to vibrationally highly excited ground electronic state molecules "hot molecules," is an intermediate step in the mechanism for the formation of fulvene isomer, la
Summary
Pentafluoropyridine (PFP) undergoes fast structural isomerisation to fulvenes when irradiated with 9R(16) CO2 laser line in the fluence range 0.5-1.5 J/cm[2]. 1’2 In contrast, strong vibrational excitation of a molecule by means of pulsed IR laser may induce internal energy transfer to the molecule’s electronic excited state Such a process is usually followed by emission of light in the visible or UV. Ratajczak et al have reported[8] that the UV flash photolysis of PFP in gas phase yields two transients which decay completely back to the original species in ms time scale Their evidence from UV flash absorption spectroscopy and mass spectroscopy characterised the intermediates to be two fulvene isomers of PFP presumably formed via excited singlet and triplet. The time resolved studies in UV flash photolysis of benzene have indicated that internal conversion to vibrationally highly excited ground electronic state molecules "hot molecules," is an intermediate step in the mechanism for the formation of fulvene isomer, la. We report that the formation of unstable fulvene isomers of PFP a. occurs by irradiation with a pulsed COa laser at a fluence of 0.5 to 1.5
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