Molecular geometry, electronic structure and optical properties study of meridianal tris(8-hydroxyquinolinato)gallium(III) with ab initio and DFT methods

We have investigated the ability of a number of chemical models to describe the geometry and optical properties of meridianal tris(8-hydroxyquinolinato)gallium(III) mer-Gaq3. It was found that the flexible basis set with diffuse and polarized orbitals (6-31+G*), in combination with electron correlation (DFTB3LYP) is required for an accurate description of the molecular geometry for the ground state. The best agreement between simulated and experimental spectra, both in terms of maximum absorption and emission wavelengths (respectively, 426 and 531 nm versus experimental values of ∼393 and ∼526 nm) was achieved with TD-B3LYP/3-21G* and that for the Stokes Shift (122 versus 133 nm) achieved using TD-B3LYP/6-31+G*. Furthermore, the Al/Ga substitution effects on the optical properties were ascribed to the induced changes in the geometrical parameters involving the metal center.