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The synthesis and photophysical study of (C^N)[Pt.sup.II]Q complexes, where C^N is a bidentate cyclometalating ligand and Q is 8-hydroxyquinoline or quinoline-8-thiol are presented. These chromophores absorb intensely in the visible region and emit in the deep-red spectral region from a quinolate-centered triplet intraligand charge-transfer excited state.

Dinuclear complexes are prepared in which a Pt(super II)-(NN)-diacetylide or Re(super 1)(NN)(CO)(sub 3)Cl chromophore is connected to a lanthanide tris luminophore via bipyrimidine as a bridging ligand. The d-block units thus act as light-harvesting components to achieve sensitized near-infrared luminescence from the lanthanide unit.

The synthesis of lanthanide complexes with a new series of tridentate ligands based on benzimidazole-substituted 8-hydroxyquinolines and the luminescent properties of the corresponding [La.sup.III] and [Nd.sup.III] chelates is described. The ligands could be used to design luminescent materials incorporating near-infrared emitting lanthanides or metal centers with square-planar ([Pt.sup.II], [Pd.sup.II]) and octahedral ([Zn.sup.II], [Ru.sup.II], [Os.sup.II], [Ir.sup.III]) coordination environment.

The syntheses of anionic catechol ligands with imide groups attached directly to the 4-position of the catechol moiety are described. The aggregation of the complexes in the diffusion layer in the course of oxidation is shown to be responsible for the concentration dependence and these complexes are electrochromic compounds in which a series of stepwise reversible redox processes leads to tunable absorbencies.

We report seven heteroleptic cationic iridium(III) complexeswithcyclometalating N-arylazoles and alkyl/aryl isocyanides, [(C∧N)2Ir(CNR)2](CF3SO3),and characterize two of them by crystal structure analysis. The complexesare air- and moisture-stable white solids that have electronic transitionsat very high energy with absorption onset at 320–380 nm. Thecomplexes are difficult to reduce and oxidize; they exhibit irreversibleelectrochemical processes with peak potentials (against ferrocene)at −2.74 to −2.37 V (reduction) and 0.99–1.56V (oxidation) and have a large redox gap of 3.49–4.26 V. Thereduction potential of the complex is determined by the azole heterocycle(pyrazole or indazole) and by the isocyanide (tert-butyl or 2,6-dimethylphenyl) and the oxidation potential by theIr–aryl fragment [aryl = 2′,4′-R2-phenyl(R = H/F), 9′,9′-dihexyl-2′-fluorenyl]. Threeof the complexes exhibit phosphorescence in argon-saturated dichloromethaneand acetonitrile solutions at room temperature with 0–0 transitionsat 473–478 nm (green color; the emission spectra are solvent-independent),quantum yields of 3–25%, and long excited-state lifetimes of62–350 μs. All of the complexes are phosphorescent at77 K with 0–0 transitions at 387–474 nm (blue to greencolor). The extremely long calculated radiative lifetimes, 0.5–3.5ms, confirm that the complexes emit from a cyclometalating-ligand-centeredexcited state. [ABSTRACT FROM AUTHOR]

We report the first comprehensive comparative synthetic,structural,electrochemical, and spectroscopic study of an extended series offluorocarbon-modified iridium(III) complexes. We prepared seven newcationic Ir(III) complexes with tert-butyl isocyanideand trifluoromethyl- or trifluoromethoxy-substituted cyclometalating2-phenylpyridines, [(C∧N)2Ir(CNtBu)2](CF3SO3), and characterizedfive of them by crystal structure analysis. The redox potentials andphotophysical properties of Ir(III) complexes are determined by thetype, position, and number of fluorocarbon groups in the cyclometalatingligand. The complexes exhibit pale blue to yellow-green phosphorescenceat room temperature with quantum yields and excited-state lifetimesup to 73% and 84 μs in solution (under argon) and 7.5% and 4.3μs in neat solid (under air). The structured and solvent-independentphosphorescence spectra, with 0–0 emission transition at 445–467nm, and the long calculated radiative lifetimes, 43–160 μs,indicate that the complexes emit from a cyclometalating-ligand-centeredtriplet excited state. Bulky fluorocarbon groups prevent intermolecularinteraction (aggregation) of the complexes, thereby minimizing red-shiftof phosphorescence color in going from solution to neat solid. [ABSTRACT FROM AUTHOR]

A facile synthesis of benzothiazole- and benzoxazole-substituted pyridine-2-carboxylic acids has been developed. These ligands form mononuclear nine-coordinate complexes [Ln([subK][sup3]-ligand)[sub2]([subK][sup1]-ligand)(H[sub2]O)[sub2]] with light and heavy trivalent lanthanides, as established from the X-ray analysis of 11 complexes. A crystal structure of a minor product, the anhydrous nine-coordinate complex [Eu([subK][sup3]-L)[sub3]], has also been determined. Photophysical studies of gadolinium chelates indicate that the triplet states of the new ligands are located at 20400-21400 cm[sup-1]. The ligands are good sensitizers of the europium luminescence with ligand-to-metal energy transfer efficiency in the range 60-100%. The overall quantum yields of the europium emission are substantial, 12-14% in the solid state, and increases to 29-39% upon replacement of two metal-coordinated water molecules with dimethylsulfoxide in solution. The luminescence of near-infrared emitting lanthanides is also sentisized, but quantum yields are much smaller, reaching 0.17% for neodymium and 1.25% for ytterbium in DMSO, while energy transfer two efficiencies for these two ions are below 50%. [ABSTRACT FROM AUTHOR]

A series of potentially dinucleating ligands, each with two bidentate imino–pyridine compartments, has been used to prepare the mononuclear complexes [Re(CO)3Cl(Ln)] (n=1–4) which each have a vacant binding site and so constitute ‘complex ligands’ for the stepwise synthesis of heterodinuclear complexes. Three of the complexes (with L1, L2 and L4) have been structurally characterised. The mononuclear complex [Re(CO)3Cl(L5)], arising from decomposition of [Re(CO)3Cl(L3)] by hydrolysis of the non-coordinated imine unit, was also isolated and structurally characterised. Luminescence studies show that these compounds are only very weak emitters. The ‘complex ligand’ [Re(CO)3Cl(L1)] has been reacted with [Ln(hfac)3]·2H2O (Ln=Yb, Er) to prepare the heterodinuclear complexes [Re(CO)3Cl(μ-L1)Ln(hfac)3] in which the {Ln(hfac)}3 unit is attached to the second bidentate imino–pyridine site of [Re(CO)3Cl(L1)]. The crystal structures of these show that the bridging ligand has to twist to accommodate the two bulky metal fragments, and that the lanthanide units have an 8-coordinate square-antiprismatic geometry. [Copyright &y& Elsevier]