Disclosed are electrophosphorescent organic metal complexes with formula (I) or (II), of either geometrical isomers, comprising two bidentate NN-type ligandsor a tetradentate NNNN-type ligand, and a transition metal. These electrophosphorescent materials are valuable to the application in organic light-emitting devices (OLEDs), including red-, orange-, or yellow-light OLEDs.