The preparation and the photophysics of organometallic Pt(II) and Ir(III) complexes with 6-chloro-3-phenylpyridazine (H6Clppdz) are reported. K2PtCl4 and IrCl3
nH2O cleanly cyclometalate with H6Clppdz, forming the corresponding chloro-bridged dimers, (6Clppdz)Pt(m-Cl)2Pt(6Clppdz) and (6Clppdz)2Ir(m-Cl)2Ir(6Clppdz)2 in good yield. These chloro-bridged dimers are cleaved with acetylacetone (Hacac) to give the corresponding monomer, (6Clppdz)Pt(acac) and (6Clppdz)2 Ir(acac), respectively. Both complexes show bright orange luminescence at room temperature and the emission wavelengths are different depending on the metal and the structure of complexes. (6Clppdz)Pt(acac) shows two sharp emission bands in shorter wavelength (lem=541 and 580 nm), while (6Clppdz)2 Ir(acac) shows a broad emission band in longer wavelength (lem=615 nm). Strong spin orbit coupling due to the heavy metal atom allows for the formally forbidden mixing of the 1MLCT with the 3MLCT and 3p-p* states.