In this study, Ir(III) complex with 4,6-diphenylquinazoline (DPQN) was designed and characterized theoretically. The Hartree-Fock (HF) method with the 3-21G(d) basis set and density functional theory (DFT) utilizing the B3LYP functional with the 6-31G(d) basis set were used for the geometry optimization and the energy level calculation of the ground state of these complexes, respectively. Excited triplet and singlet states are examined using the time-dependent density functional theory (TD-DFT). As a result, it was found that these complexes produced a deep red emission due to the elongated conjugation length. The Ir(III) complex with DPQN ligands exhibits the large emission efficiency and emits light of the deep red wavelength. (c) 2006 Elsevier B.V. All rights reserved.