A DFT study of the ionization and electron attachment of 2-azido pyridine

作者：Elshakre Mohamed^*

来源：Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy , 2015, 138: 146-157.

DOI：10.1016/j.saa.2014.10.085

• Excited states S-n
• Cationic state D-0(+)
• Anionic state D-0(-)
• Vertical excitation energy
• Ionization energy
• Electron attachment energy

A DFT study using B3LYP/6-31G(d,p) level of theory is pursued to investigate the energy and geometry changes of 2-azido pyridine isomers in the S-0, D-0(+), and D-0(-). In S-0, cis-2 azidopyridine is the most stable, followed by cyclic tetrazole and trans isomer is the least stable. In D-0(+), the cis isomer is the most stable, followed by trans isomer, and tetrazole isomer is the least stable. In the D-0(-) state, the trans form is the most stable, followed by the cis and the tetrazolo form is the least stable. Single point vertical excitation energy calculations of the cis form gave four excited states at 266.4, 239.4, 199.4, and 196.1nm, all having pi-pi* character. For trans isomer, five excited states at, 256.7, 250.3, 229.7, 199.0, 197.0nm all resulting from pi-pi* transitions. For the tetrazole isomer, seven excited states at 269.3, 242.7, 198.0, 187.2, 183.9, 182.1, 178.7nm all resulting from pi-pi* transitions. The geometries of the 3 isomers show noticeable changes in bond lengths, bond angles and dihedral angles, upon ionization and electron attachment. The ionization results in a remarkable variation of the NBO atomic charges as a result of ionization and electron attachment. where electron density of HOMO of the D-0(+) state is found to be much lower than that of the HOMO of the S-0 in the case of ionization. The dipole moment calculations show that tetrazole isomer has the largest polarization in the S-0 state, followed by cis isomer and trans isomer is the least polarized. The same pattern is found in the D-0(+) state. In the D-0(-) state, trans isomer is the highest polarized, followed by the cis, and tetrazole isomer is the least polarized. The rotational constants calculations of cis- isomer show that the cation is elongated along the long in-plane axis and compressed along the two short out-of-plane axes while the anion is compressed along the long in-plane axis, and elongated along the two short out-of plane axes. The cation and anion of trans isomer show similar behavior to the cis isomer. The cation of cyclic tetrazole, is compressed along the long in-plane axis and elongated along the two short out-of-plane axes, while the anion elongates along the 3 mutually perpendicular axes.

• 出版日期2015-3-5