Molecular and electronic structures of Mn-doped tris-8-hydroxyquinolinate gallium: DFT calculation and experiment

Molecular and electronic structures of Mn-doped tris-8-hydroxyquinolinate gallium (Gaq3) were investigated by first-principle density-functional theory (DFT) calculations and Fourier transform-infrared spectroscopy (FTIR) and photoluminescence (PL) spectra measurements. Calculation results show that the lowest unoccupied molecular orbital (LUMO) sets reside mainly on N2, N3 p states, as well as on the p states of their third-nearest-neighbor C atoms. The doped Mn atoms prefer to be located at the ligand center. The electrons deplete from the Mn atom and accumulate mainly on the C, N atoms within the pyridyl ring of ligand A. The magnetic moment is mainly localized around the d orbital of Mn atom and the 2p states of C and N atoms on pyridyl ring are also spin polarized due to the hybridization with Mn 3d states. The positive charged Mn ions lead to an electron trap site in the energy gap and a red luminescence appears in PL spectra, which may be related to the MLCT excited states.