| Abstract
| - The preparation, photophysics, and solid state structures of octahedral organometallic Ir complexes with severaldifferent cyclometalated ligands are reported. IrCl3·nH2O cleanly cyclometalates a number of different compounds(i.e., 2-phenylpyridine, 2-(p-tolyl)pyridine, benzoquinoline, 2-phenylbenzothiazole, 2-(1-naphthyl)benzothiazole,and 2-phenylquinoline), forming the corresponding chloride-bridged dimers, C∧N2Ir(μ-Cl)2IrC∧N2 (C∧Nis acyclometalated ligand) in good yield. These chloride-bridged dimers react with acetyl acetone (acacH) and otherbidentate, monoanionic ligands such as picolinic acid (picH) and N-methylsalicylimine (salH), to give monomericC∧N2Ir(LX) complexes (LX = acac, pic, sal). The emission spectra of these complexes are largely governed bythe nature of the cyclometalating ligand, leading to λmax values from 510 to 606 nm for the complexes reportedhere. The strong spin−orbit coupling of iridium mixes the formally forbidden 3MLCT and 3π−π* transitionswith the allowed 1MLCT, leading to a strong phosphorescence with good quantum efficiencies (0.1−0.4) androom temperature lifetimes in the microsecond regime. The emission spectra of the C∧N2Ir(LX) complexes aresurprisingly similar to the fac-IrC∧N3 complex of the same ligand, even though the structures of the two complexesare markedly different. The crystal structures of two of the C∧N2Ir(acac) complexes (i.e., C∧N = ppy and tpy)have been determined. Both complexes show cis-C,C‘, trans-N,N‘ disposition of the two cyclometalated ligands,similar to the structures reported for other complexes with a “C∧N2Ir” fragment. NMR data (1H and 13C) supporta similar structure for all of the C∧N2Ir(LX) complexes. Close intermolecular contacts in both (ppy)2Ir(acac) and(tpy)2Ir(acac) lead to significantly red shifted emission spectra for crystalline samples of the ppy and tpy complexesrelative to their solution spectra.
- The preparation, photophysics, and solid state structures of several octahedral, organometallic Ir complexes are reported. All of the compounds have two cyclometalated organometallic ligands and have photophysical properties very similar to those of their tris chelate analogues. These complexes are highly phosphorescent, with emission maxima ranging from 510 to 610 nm, have phosphorescent quantum efficiencies between 0.1 and 0.4, and have microsecond lifetimes at room temperature.
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