CH/N substituted mer-Gaq3 and mer-Alq3 derivatives:: An effective approach for the tuning of emitting color

Equilibrium geometry configurations of the "CH"/N substituted Alq3 and Gaq3 derivatives are calculated by density functional theory (B3LYP/6-31G*). The frontier molecular orbital and gap energy calculations for all complexes have been performed at the HF/6-31G* level. It was shown that, compared to the pristine molecules, the HOMO and LUMO are stabilized, the net effect being however an increasing/decreasing of the gap (E-g) depending on the position of the substituted group. On the basis of the equilibrium geometries, the effect of the substitution on the absorption and emission spectra was evaluated using TDB3LYP/3-21G*. It was shown that the change of "CH"/N substituted position on 8-hydroxyquinoline ligand is a powerful approach for the tuning of emitting color. An important blue shift was predicted for 5-substituted 8-hydroxyquinoline derivatives, an important red one being observed for 4-substituted ones. Interestingly, relatively significant blue and red shifts were also predicted for the 7- and 2-substituted derivatives. In this work, the correlation between the spectrum shifts and the metal-ligand bonding is also discussed.