Electronic and optical properties of facial tris (8-hydroxyquinoline) aluminum derivatives

Abstract

In this study, we substitute facial Alq3 with (Mg) in positions 7 and 5 as electron donating group (EDG) and (-Cl), (-P) and (-S) in position 7 as electron withdrawing groups (EWD). The ground and the first excited states geometries of facial Alq3 and their derivatives are optimized using B3lyp/6-31G (d) methods. To analyse the electric transitions in these materials, the frontier molecular orbitals (FMOs) are calculated. It was found that the highest occupied molecular orbital (HOMO) is mainly situated on the phenoxide ring, while the lowest unoccupied molecular orbital (LUMO) is situated on the pyridyl ring, the atom C9 of phenoxide or in EWD atom. The dipole moment is calculated and analysed. The absorption and emission spectra are calculated with the TD-DFT/6-31G (d) method. It is seen that the electron donating or electron withdrawing groups in 7 positions caused a red shift in the absorption and emission spectra; what means that these substitutes have a significant effect on fac-Alq3.