Sunghwan Kim - Infrared, raman, and ultraviolet absorption spectra and theoretical calculations and structure of 2,6-difluoropyridine in its ground and excited electronic states

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      Publication Details (including relevant citation   information):

      H.-L. Sheu, S.   Kim, and J. Laane;

      Journal of Physical Chemistry A,   2013117, 13596.



      The infrared and Raman spectra of 2,6-difluoropyridine (26DFPy)   along with ab initio and DFT computations have been used to   assign the vibrations of the molecule in its S0 electronic ground   state and to calculate its structure. The ultraviolet absorption   spectrum showed the electronic transition to the S1(π,π*) state   to be at 37 820.2 cm-1. With the aid of ab initio computations   the vibrational frequencies for this excited state were also   determined. TD-B3LYP and CASSCF computations for the excited   states were carried out to calculate the structures for the S   1(π,π*) and S2(n,π*) excited states. The CASSCF results predict   that the S1(π,π*) state is planar and that the S2(n,π*) state has   a barrier to planarity of 256 cm-1. The TD-B3LYP computations   predict a barrier of 124 cm-1 for the S1(π,π*) state, but the   experimental results support the planar structure. Hypothetical   models for the ring-puckering potential energy function were   calculated for both electronic excited states to show the   predicted quantum states. The changes in the vibrational   frequencies in the two excited states reflect the weaker π   bonding within the pyridine ring.


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