Ru(II) polypyridine complexes: photophysics, photochemistry, eletrochemistry, and chemiluminescence

The synthesis and photophysical study of a family of cyclometalated iridium(III) complexes are reported. The iridium complexes have two cyclometalated (C∧N) ligands and a single monoanionic, bidentate ancillary ligand (LX), i.e., C∧N2Ir(LX). The C∧N ligands can be any of a wide variety of organometallic ligands. The LX ligands used for this study were all β-diketonates, with the major emphasis placed on acetylacetonate (acac) complexes. The majority of the C∧N2Ir(acac) complexes phosphoresce with high quantum efficiencies (solution quantum yields, 0.1−0.6), and microsecond lifetimes (e.g., 1−14 μs). The strongly allowed phosphorescence in these complexes is the result of significant spin−orbit coupling of the Ir center. The lowest energy (emissive) excited state in these C∧N2Ir(acac) complexes is a mixture of 3MLCT and 3(π−π*) states. By choosing the appropriate C∧N ligand, C∧N2Ir(acac) complexes can be prepared which emit in any color from green to red. Simple, systematic changes in the C∧N ligands, whic...

Highly phosphorescent bis-cyclometalated iridium complexes: synthesis, photophysical characterization, and use in organic light emitting diodes.

Photophysics, photochemistry and solar energy conversion with tris(bipyridyl)ruthenium(II) and its analogues

Electrogenerated chemiluminescence (also called electrochemiluminescence and abbreviated ECL) is the process whereby species generated at electrodes undergo high-energy electron-transfer reactions to form excited states that emit light. The first detailed ECL studies were described by Hercules and Bard et al. in the mid-1960s, although reports concerning light emission during electrolysis date back to the 1920s by Harvey. After about 40 years study, ECL has now become a very powerful analytical technique and been widely used in the areas of, for example, immunoassay, food and water testing, and biowarfare agent detection. ECL has also been successfully exploited as a detector of flow injection analysis (FIA), high-performance liquid chromatography (HPLC), capillary electrophoresis, and micro total analysis (μTAS). Figure 1 illustrates a time line of various events in the development of ECL. A literature survey using SciFinder Scholar reveals that more than 2000 journal articles, book chapters, and patents on various topics of ECL have been published. The overall number of publications, as shown in Figure 2, has increased exponentially over the past 20 years, of which 40–50% were biorelated. Similar amounts of ECL papers could be also found from the Thomson ISI Web of Science as well as † Telephone (601) 266 4716; fax (601) 266 6075; e-mail wujian.miao@ usm.edu. Wujian Miao received his undergraduate diploma in chemistry from Nantong University (Nantong, China) in 1982, his M.Sc. degree in analytical chemistry from Zhongshan University (Guangzhou, China, with Jinyuan Mo) in 1991, and his Ph.D. degree in electrochemistry from Monash University (Melbourne, Australia, with Alan M. Bond) in 2000. He then served as a Research Scientist in CSIRO (Melbourne, Australia), followed by a postdoctoral fellowship at the University of Texas at Austin with Allen J. Bard in 2001. Since 2004 he has served as an assistant professor of chemistry at the University of Southern Mississippi.

Electrogenerated Chemiluminescence and Its Biorelated Applications

The synthesis, electrochemistry, and photophysics of a series of square planar Pt(II) complexes are reported. The complexes have the general structure C∧NPt(O∧O),where C∧N is a monoanionic cyclometalating ligand (e.g., 2-phenylpyridyl, 2-(2‘-thienyl)pyridyl, 2-(4,6-difluorophenyl)pyridyl, etc.) and O∧O is a β-diketonato ligand. Reaction of K2PtCl4 with a HC∧N ligand precursor forms the chloride-bridged dimer, C∧NPt(μ-Cl)2PtC∧N, which is cleaved with β-diketones such as acetyl acetone (acacH) and dipivaloylmethane (dpmH) to give the corresponding monomeric C∧NPt(O∧O) complex. The thpyPt(dpm) (thpy = 2-(2‘-thienyl)pyridyl) complex has been characterized using X-ray crystallography. The bond lengths and angles for this complex are similar to those of related cyclometalated Pt complexes. There are two independent molecular dimers in the asymmetric unit, with intermolecular spacings of 3.45 and 3.56 A, consistent with moderate π−π interactions and no evident Pt−Pt interactions. Most of the C∧NPt(O∧O) complexes...

Synthesis and characterization of phosphorescent cyclometalated platinum complexes.

Temperature dependence of the luminescence of cyclometalated palladium(II), rhodium(III), platinum(II), and platinum(IV) complexes

Luminescence of ortho-metallated platinum(II) complexes

The photochemical and luminescence behavior of the orthometalated Pt(thpy)/sub 2/ complex, where thpy/sup -/ is the ortho-C-deprotonated form of 2-(2-thienyl)pyridine, has been studied under a variety of experimental conditions, and the mechanisms of the excited-state reactions and of the subsequent thermal processes are discussed In degassed CH/sub 3/CN the complex is not photosensitive and exhibits luminescence from the lowest triplet metal-to-ligand charge-transfer (/sup 3/MLCT) excited state with phi/sub em/ = 026 and tau = 24 mus In CH/sub 2/Cl/sub 2/, CHCl/sub 3/, or CH/sub 3/CN/CH/sub 2/Cl/sub 2/ solvents, the complex maintains its luminescent properties and undergoes a photooxidative addition reaction with formation of Pt(thpy)/sub 2/(Cl)(R) (R = CH/sub 2/Cl or CHCl/sub 2/) as the sole observed product In the mixed solvent, the quantum yield of the photoreaction increases with increasing CH/sub 2/Cl/sub 2/ concentration In neat CH/sub 2/Cl/sub 2/, the quantum yield of the photoreaction is 030 and 010 for 313- and 430-nm excitation, respectively In CH/sub 2/Cl/sub 2/, complete quenching of the luminescent /sup 3/MLCT excited state by anthracene via an energy-transfer mechanism is accompanied by only partial quenching of the photoreaction By contrast, oxygen is a better quencher for the photoreaction than for the luminescence emission In bothmore » cases the fraction of quenched reaction depends on the excitation wavelength« less

Photochemistry of the orthometalated cis-bis(2-(2-thienyl)pyridine)platinum(II) complex in halocarbon solvents

The absorption spectra, luminescence spectra, and luminescence lifetimes of the isomeric [M(bph)(bpy)] and [M(phpy)2] complexes M = Pt(II) or Pd(II), bph2− = 1,1′-biphenyl-2,2′-diyl dianion, phpy− = 2-phenylpyridine-2′-yl anion, and bpy = 2,2′-bipyridine have been investigated and compared with those of [M(bpy)2]2+ complexes and of the free protonated ligands H2bph, Hbpy+, and Hphpy. In the absorption spectra, the region below 320 mm is dominated by ligand-centered (LC) transitions, whereas metal-to-ligand charge transfer (MLCT) transitions are responsible for the bands present in the near UV/VIS region. The MLCT bands move to higher energies on replacing Pt with Pd and in going from [M(bph)(bpy)] to the [M(phpy)2] isomer. For the mixed-ligand complexes, evidence for both M bph2− (at higher energies) and M bpy bands is found. The structured luminescence observed at 77 K shows lifetimes of 4.0 and 1.1 μs for [Pt(phpy)2] and [Pt(bph)(bpy)], respectively, and 480 and 250 μs for the analogous Pd complexes. On the basis of the energy and lifetime data, the luminescence of the Pt(II) complexes is assigned to the lowest triplet MLCT excited state, whereas for the Pd complexes the luminescent state is thought to result from a mixture of MLCT and LC triplet levels.

Absorption Spectra and Luminescence Properties of Isomeric Platinum (II) and Palladium (II) Complexes containing 1,1′-biphenyldiyl, 2-phenylpyridine, and 2,2′-bijpyridine as ligands

D. Sandrini

Papers

Temperature dependence of the luminescence of cyclometalated palladium(II), rhodium(III), platinum(II), and platinum(IV) complexes

Luminescence of ortho-metallated platinum(II) complexes

Photochemistry of the orthometalated cis-bis(2-(2-thienyl)pyridine)platinum(II) complex in halocarbon solvents

Absorption Spectra and Luminescence Properties of Isomeric Platinum (II) and Palladium (II) Complexes containing 1,1′-biphenyldiyl, 2-phenylpyridine, and 2,2′-bijpyridine as ligands

Quantum yield of formation of the lowest excited state of Ru(bpy)2+3 and Ru(phen)2+3