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Semiconducting (conjugated) polymers have several properties that are advantageous for photonic applications: they have high fluorescence efficiencies (>60 %), emit at wavelengths that span the entire visible spectrum, are mechanically flexible, and can be deposited as uniform thin films by casting from solution. Since the fabrication of the first polymer light-emitting diode (LED) in 1990, [1] there has been extensive research on polymer LEDs and many improvements have been made. [2±4] Single-color displays fabricated with arrays of polymer LEDs will soon be commercially available. Full color displays will require pure red, green, and blue emission.Obtaining pure emission colors from conjugated polymers or small organic molecules is difficult because their emission spectra typically have a full width at half maximum (FWHM) of 50±200 nm. Efficient, pure red-emitting polymer LEDs are particularly hard to make because the human eye is more sensitive to orange emission than red; if the spectrum falls even slightly in the orange, the perceived color is ªorangish redº. Red LEDs can be made by filtering out orange emission or by using polymers or dyes whose emission starts in the red and extends into the infrared, but these LEDs are inefficient because only part of their emission is useful. In contrast to organic chromophores, rare earth ions have very sharp emission spectra (FWHM < 4 nm). [5] In this paper we show that pure red emission can be achieved in polymer LEDs by transferring energy from blue-emitting conjugated polymers to europium complexes. Similar methods have been used to make red LEDs from small organic molecules. [6±10] We show that blends of Eu complexes in poly[2-(6¢-cyano-6¢-methyl-heptyloxy)-1,4-phenylene] (CN-PPP) have an emission spectral linewidth (FWHM) of only 3.5 nm, a photoluminescence (PL) efficiency of 27 %, and an electroluminescence (EL) efficiency of 1.1 %. These blends could be useful as a source of pure red light for full color displays or for photonic devices that require monochromatic light.To incorporate Eu 3+ into conjugated polymers, we synthesized a family of soluble Eu complexes with b-diketonate ligands, codissolved the complexes and polymers in a solvent, and cast films. We chose b-diketonate ligands because they sensitize Eu 3+ emission. [5,11] The sensitization process is as follows: the ligand absorbs energy, undergoes intersystem crossing into a triplet state, and then transfers its energy to the Eu 3+ ion. [12,13] Thus, the first design rule for making fluorescent Eu complexes is that the triplet level of the ligand must be higher in energy than the emissive level ( 5 D 0 ) of Eu 3+ . A second design rule is imposed by the need for energy transfer from the polymer to the rare earth complex. In order to transfer energy from a conjugated polymer to the ligands of a Eu complex by dipole coupling (Förster transfer), the emission spectrum of the polymer and the absorption spectrum of the ligand must overlap. [14,15] Since the ligands whose triplet level lies above the 5 D 0...

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6-C6H3-i-Prz; OR = OCMe(CF3),, OCMe(CFJ) form fivecoordinate adducts upon addition of PMe3 or quinuclidme. PMe3 attacks the C/N/O face of the pseudotetrahedral complexes to give chiral TBP species in which the phosphine is bound in an axial position and the imido and alkylidene ligands lie in the equatorial plane. Two isomers containing syn and anti rotamers of the alkylidene ligand are observed. The syn rotamer forms first; the anti rotamer is the final product. PMe3 binds weakly when OR = 0-t-Bu and is lost readily in vacuo. Quinuclidine adds to either the C 0/0 face or N/O/O face to give an achiral syn isomer and to the C/N/O face to of syn and anti forms is observed with time. An X-ray structure of syn-Mo(CH-t-Bu)(NAr)[OCMe-(CF,),I2(PMe3) shows that the t-Bu group points toward the imido ligand and the phenyl ring of the imido ligand lies approximately in the equatorial plane in a relatively crowded coordination environment (a = 10.979 (4) A, b = 17.945 (7) A, c = 18.375 (8) A, 19 = 106.34 (3)O, 2 = 4, V = 3474 (4) AS, p = 1.490 g/cm3, R = 0.037, R, = 0.045). Pyridine adducts of Mo complexes containing the 2,6-dichlorophenoxide ligand also have been characterized. Three isomers of fivecoordinate molybdenum or tungsten complexes containing a cis-or trans-2-butenylidene ligand and quinuclidine are found at equilibrium, syn and anti rotamers of the chiral core previously described and a syn rotamer with an achiral core. An X-ray structure of anti-W(tram-CHCH=CHMe)(NAr)[OCMe(CF3)z]2(quin) showed the expected trigonal-bipyramidal core with alkylidene and imido ligands occupying equatorial sites and OCMe(CF3)2 ligands occupying one axial and one e uatorial site (a = 12.972 (9) A, b = 18.049 (7) A, c = 15.038 (9) A, p = 92.07 (3)O, 2 = 4, V = 3518 (6) A?, p = 1.673 g cm3, R1 = 0.038, R, = 0.040). The only significant difference between the structure in the equatorial plane. Syn and anti rotamers in five-coordinate adducts have been shown to interconvert after losing the base in several cases. The barrier to rotation of the alkylidene ligand has been measured in several four-coordinate species and shown to lie in the range AG*= = 15-18 kcal mol-'. These findings are discussed in relation to the proposed mechanism of olefin metathesis by pseudotetrahedral complexes of the type M(CHR')(NAr)(OR),.give an anti chiral T 6 P species analogous to that formed for the PMe3 adduct. An equilibrium mixture of this anti adduct an d the syn adduct described above is that the anti adduct is markedly less crowded

The complex tris[1(N-ethylcarbazolyl)(3A,5A-hexyloxybenzoyl)methane](phenanthroline)europium 1 incorporates a phenanthroline ligand for electron transport and a carbazole fragment in the diketonate ligand for hole transport; furthermore, the six hexyloxy groups prevent crystallization and allow for the formation of transparent clear films directly from solution; the photoluminescence from films of 1 is nearly monochromatic, characteristic of the europium ion and proceeds with an efficiency of 50(3)%; light emitting diodes(LEDs) were fabricated using the simplest possible device architecture comprising an anode (ITO), a layer of 1 and a cathode (Ca); a second LED configuration with a PVK layer on top of the ITO was also investigated; the performance of the two types of devices is discussed. † Complete details for the synthesis of 1 (PDF). The material is available free of charge via the Internet at http://pubs.acs.org.Scheme 1 Reagents and conditions: i, NaH/dimethoxyethane; ii, NaOH, EuCl 3 (H 2 O) 6 , ethanol; iii, phenanthroline, toluene.