Abstract An iridium(III) pyrimidine complex Ir(NDMP)2acac (NDMP = 2-(2-naphthyl)-4,6-dimethylpyrimidine, acac = acetylacetonate) was synthesized and characterized by 1H NMR, 13C NMR, MALDI-TOF mass spectrometry and elemental analysis. An unexpected mononuclear complex Ir(NDMP)2(Cl)(H2O) was obtained in the process of preparing the Cl-bridged dimer [Ir(NDMP)2Cl]2. The crystal structures of these complexes were determined by X-ray single crystal diffraction and contrastively studied. The photoluminescence spectrum of Ir(NDMP)2acac exhibits a yellow emission at 560 nm. The HOMO and LUMO energy levels of Ir(NDMP)2acac were calculated to be − 5.14 eV and − 2.80 eV respectively.