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The synthesis and characterization of neutral heteroleptic molecular iridium(III) complexes with (2,4-difluoro)phenylpyridine and different pyridine-1,2,4-triazole ligands are described. The studies have shown high external quantum efficiencies and color points better than the standard for blue iridium(III) bis[(4,6-difluorophenyl)pyridinato-N,[C.sup.2]]picolinate.

The synthesis and the properties of the tetranuclear class of lanthanide arrays with the general formula [[Ln.sub.4][L.sub.9]([[mu].sub.3]-OH)][(Cl[O.sub.4]).sub.2] (tetra-[Ln.sub.4][L.sub.9]) are described. The factors affecting the reversible switching between the trinuclear architecture [[Ln.sub.3][L.sub.6]([[mu].sub.3]-OH)[([H.sub.2]O).sub.3]][(Cl[O.sub.4]).sub.2] (tris-Ln[L.sub.2]) and the tetranuclear architecture (tetra-[Ln.sub.4][L.sub.9]) are analyzed.

The coordination-driven self-assembly of four different trigonal prisms from 3 equiv of one of four different tetrapyridyl star connectors and 6 equiv of a platinum linker dication in nitromethane is presented. The use of a conformationally chiral star connector leads to a conformationally chiral prism when connector arm ends attached to a vertex have a strongly correlated twist sense and chirality is communicated across polyhedral faces, edges, and vertices.

Man-made molecular rotors are discussed form the point of view of their potential utility for 'molecular machinery'. A gradual shift of emphasis of studies of rotor molecules floating freely in solution to systems is expected in which they are mounted on the surfaces or inside solids.

Theknown (tetraphenyl-η4-cyclobutadiene)-η5-cyclopentadienylcobalt (1) and a series of itsnew substituted derivatives have been prepared. The electronic statesof a few representatives have been characterized by absorption andmagnetic circular dichroism. Time-dependent density functional theoryhas been used to arrive at spectral assignments for several prominentlow-energy bands. The absorption spectra of the radical ions of 1have also been recorded. [ABSTRACT FROM AUTHOR]

Neutral heteroleptic mononuclear iridium(l II) complexes with (2,4-difluoro)phenylpyridine and different pyridine-1,2,4-triazole ligands were synthesized and fully characterized. We investigated the effects of substituents in the 5-position of the triazole ring on the photophysical and electrochemical behavior. Increasing the electron-withdrawing capabilities generally leads to a lowering of the HOMO level with a consequent slight widening of the HOMO-LUMO gap and a blue shift in emission. The complexes reported exhibit high emission quantum yields and long luminescent lifetimes, typical of iridium(lll) complexes, and most of them show reversible redox processes in solution. Also, many of the complexes reported here have been obtained as single crystals suitable for X-ray crystallography. Two of the complexes were further tested as phosphorescent dyes in OLED devices and showed high external quantum efficiencies (~7%) and color points better than the "standard" for blue iridium(lll) bis[(4,6-difluorophenyl)-pyridinato-N,C²′]picolinate (Flrpic). We also report the full electrochemical investigation of Flrpic in different solvents. [ABSTRACT FROM AUTHOR]

The synthesis and photophysical and electrochemical characterisation of new heteroleptic iridium complexes with electron-withdrawing sulfonyl groups and fluorine atoms bound to phenylpyridine ligands are reported. The emission energy of these materials strongly depends on the position of the sulfonyl groups and on the number of fluorine substituents. A 90 nm wide tuning range of photoluminescence from the blue-green (lambda(em)=468 nm) of iridium(III)bis[2-(4'-benzylsulfonyl)phenylpyridinato-N,C2'][3-(pentafluorophenyl)-pyridin-2-yl-1,2,4-triazolate] to the orange (lambda(em)=558 nm) of iridium(III)bis[2-(3'-benzylsulfonyl)phenylpyridinato-N,C2'](2,4-decanedionate) has been achieved. Emission quantum yields ranging from 47 to 71% have also been found for degassed solutions of the complexes, and a surprisingly high value of 16% was recorded for iridium(III)bis[2-(5'-benzylsulfonyl-3',6'-difluoro)phenylpyridinato-N,C2'](2,4-decanedionate) in air-equilibrated dichloromethane. A unusual stereochemistry of the benzylsulfonyl-substituted dimer and heteroleptic complexes has been detected by (1)H NMR spectroscopy, and is characterised by the mutual cis disposition of the pyridyl nitrogen atoms of the phenylpyridine ligands, which differs from the most common trans arrangement reported in the literature.

The pinene-bipyridine carboxylic derivatives (+)- and (-)-HL, designed to form configurationally stable lanthanide complexes, proved their effectiveness as chiral building blocks for the synthesis of lanthanide-containing superstructures. Indeed a self-assembly process takes place with complete diastereoselectivity between the enantiomerically pure ligand L(-) and Ln(III) ions (La, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er), thus leading to the quantitative formation of a trinuclear supramolecular architecture with the general formula [Ln(3)(L)(6)(mu(3)-OH)(H(2)O)(3)](ClO(4))(2) (abbreviated as tris(Ln[L](2))). This class of C(3)-symmetrical compounds was structurally characterized in the solid state and solution. Electrospray (ES) mass spectrometric and (1)H NMR spectroscopic analyses indicated that the trinuclear species are maintained in solution (CH(2)Cl(2)) and are stable in the investigated concentration range (10(-2)-10(-6) m). The photophysical properties of the ligand HL and its tris(Ln[L](2)) complexes were studied at room temperature and 77 K, thus demonstrating that the metal-centered luminescence is well sensitized both for the visible and near-IR emitters. The chiroptical properties of tris(Ln[L](2)) complexes were investigated by means of circular dichroism (CD) and circularly polarized luminescence (CPL). A high CD activity is displayed in the region of pi-pi* transitions of bipyridine. CPL spectra of tris(Eu[(+)-L](2)) and tris(Tb[(+)-L](2)) present large dissymmetry factors g(em) for the sensitive transitions of Eu(III) ((5)D(0)-->(7)F(1), g(em)=-0.088) and Tb(III) ((5)D(4)-->(7)F(5), g(em)=-0.0806). The self-recognition capabilities of the system were tested in the presence of artificial enantiomeric mixtures of the ligand. (1)H NMR spectra identical to those of the enantiomerically pure complexes and investigations by CD spectroscopic analysis reveal an almost complete chiral self-recognition in the self-assembly process, thus leading to mixtures of homochiral trinuclear structures.