Synthesis and characterization of phosphorescent cyclometalated iridium complexes

The preparation, photophysics, and solid state structures of octahedral org anometallic Ir complexes with several different cyclometalated ligands are reported. LrCl3 . nH(2)O cleanly cyclometalates a number of different compo unds (i.e., 2-phenylpyridine, 2-(p-tolyl)pyridine, benzoquinoline, 2-phenyl benzothiazole, 2-(1-naphthyl)benzothiazole, and 2-phenylquinoline), forming the corresponding chloride-bridged dimers, C boolean ANDN(2)Ir(mu -Cl)(2)I rC boolean ANDN(2) (C boolean AND Nis a cyclometalated ligand) in good yiel d. These chloride-bridged dimers react with acetyl acetone (acacH) and othe r bidentate, monoanionic ligands such as picolinic acid (picH) and N-methyl salicylimine (salH)\ to give monomeric C boolean ANDN(2)Ir(LX) complexes (L X = acac, pie, sal). The emission spectra of these complexes are largely go verned by the nature of the cyclometalating ligand, leading to lambda (max) values from 510 to 606 nm for the complexes reported here. The strong spin -orbit coupling of iridium mixes the formally forbidden (MLCT)-M-3 and 3 pi -pi* transitions with the allowed (MLCT)-M-1, leading to a strong phosphore scence with good quantum efficiencies (0.1-0.4) and room temperature lifeti mes in the microsecond regime. The emission spectra of the C boolean ANDN(2 )Ir(LX) complexes are surprisingly similar to the fac-IrC boolean ANDN(3) c omplex of the same ligand, even though the structures of the two complexes are markedly different. The crystal structures of two of the C boolean ANDN (2)Ir(acac) complexes (i.e., C boolean ANDN = ppy and tpy) have been determ ined. Both complexes show cis-C,C', trans-N,N' disposition of the two cyclo metalated ligands, similar to the structures reported for other complexes w ith a "C boolean ANDN(2)Ir" fragment. NMR data (H-1 and C-13) support a sim ilar structure for all of the C boolean ANDN(2)Ir(LX) complexes. Close inte rmolecular contacts in both (ppy)(2)Ir(acac) and (tpy)(2)Ir(acac) lead to s ignificantly red shifted emission spectra for crystalline samples of the pp y and tpy complexes relative to their solution spectra.