Abstract: The molecular structures of the ground state and the first singlet excited state for organometalic complexes bis(8-hydroxyquinoline) beryllium (BeQ₂) and its three derivatives were optimized with the DFT B3LYP method and ab initio "configuration interaction with single excitations"(CIS) method respectively. The frontier molecular orbital characteristics and energy levels of BeQ₂ have been analyzed systematically in order to study the electronic transition mechanism. Electronic spectrum property of complexes have been investigated with time-dependent density functional theory(TD-DFT), which indicates that the emissions of BeQ₂ and its derivatives originate from the electronic π→π * transitions within ligands. These theoretical results suggest that it might be possible to tune the emission wavelengths and improve charge transfer properties through the effect of ligand substituent on the distribution of frontier molecular orbital.

Key words: Bis(8-hydroxyquinoline) beryllium, Electronic spectrum, Time-dependent density functional theory(TD-DFT)