A computational insight into the Reactivity, aromaticity, and absorption spectra of six membered isoelectronic N-heteroarenes

Reactivity, aromaticity, and absorption spectra of pyridine, pyridazine, pyrimidine, pyrazine, 1,2,3-triazine, 1,2,4-triazine and 1,2,5-triazine are studied in the light of Density functional theory (DFT) at B3LYP/6-31+G(d,p) level of theory. Frontier molecular orbitals are studied, both HOMO and LUMO energies and their shapes changes on increasing the number of N-atom in the rings. Global hardness (ɳ) and global electrophilicity (ω) values comply with both MHP and MEP. In plane and out of plane aromaticity vary significantly with change in the position and number of N-atom in the ring, and maximum aromaticity is found around 1.0 Å from the molecular plane. Time dependent density functional theory (TDDFT) is study has suggested their absorption maxima primarily in the UV-region, and shows both red and blue shift depending upon the position and number of N-atom in the heteroarenes.