Synthesis and characterization of phosphorescent platinum complexes containing phenylpyridazine

Synthesis and characterization of a series of square planar Pt(II)-phenylpyridazine complexes are reported. The complexes have the general structure of (C–N)Pt(O–O), where HC–N is 3-phenyl-pyridazine (ppdz), 3-(3′-trifluoromethylphenyl)pyridazine (3′tfmppdz), 3-(3′-methoxyphenyl)-pyridazine (3′meoppdz), 3-(4′-methoxyphenyl)pyridazine (4′meoppdz), or 3-phenyl-6-chloro-pyridazine (6Clppdz) and HO–O is acetylacetone (Hacac). Reaction of K₂PtCl₄ with a HC–N ligand forms the dimer, (C–N)Pt(μ-Cl)₂Pt(C–N), which is cleaved with Hacac to give the corresponding monomer, (C–N)Pt(O–O). The emission characteristics of these complexes are governed by the substituents of the cyclometalating ligands, showing emission λ_max values from 508 to 610 nm. Strong spin-orbit coupling of the platinum atom allows for the formally forbidden mixing of the ¹MLCT with the ³MCLT and ³(π–π*) states.