Effect of phosphorus on the electronic and optical properties of naphthoxaphospholes: theoretical investigation

<p>Density functional theory (DFT) and time-dependent DFT calculations were performed to elucidate the electronic and optical properties of 2-R-naphthol[2,3-<i>d</i>]oxaphospholes (R-NOPs). On the basis of the calculated results, the poor π overlap between the 3<i>p</i><sub>z</sub> orbital of P atom and the 2<i>p</i><sub>z</sub> orbitals of other atoms and increasing polarity of P atom result in a reduced energy gap between the highest occupied molecular orbital and the lowest unoccupied molecular orbital. When these two effects are considered simultaneously, the absorption energies obtained for the S<sub>1</sub> state can be below 3.00 eV according to replace the P atom of oxaphosphole ring by As atom (increasing the poor π overlap) and change the functional groups (increasing polarity). The origin of these two effects is the inherent size of the 3<i>p</i> orbital of P atom. The role of P atom in the control of the electronic and optical properties of R-NOPs is clearly elucidated.</p>