Electroluminescent devices based on rare-earth tetrakis beta-diketonate complexes

In this paper the synthesis, photo luminescence and electroluminescence investigation of the novel tetrakis beta-diketonate of rare-earth complexes such as M[Eu(dbM)(4)] and M[Tb(acac)(4)] with a variety of cationic ligands, M=Li(+), Na(+) and K(+) have been investigated. The emission spectra of the Eu(3+) and Tb(3+) complexes displayed characteristic narrow bands arising from intraconfigurational transitions of trivalent rare-earth ions and exhibited red color emission for the Eu(3+) ion ((5)D(0) -> F(J), J=0-6) and green for the Tb(3+) ion ((5)D(4) -> (7)F(J), J = 6-0). The lack of the broaden emission bands arising from the ligands suggests the efficient intramolecular energy transfer from the dbm and acac ligands to Eu(3+) and Tb(3+) ions, respectively. In accordance to the expected, the values of PL quantum efficiency (eta) of the emitting (5)D(0) state of the tetrakis(beta-diketonate) complexes of Eu(3+) were higher compared with those tris-complexes. Therefore, organic electroluminescent (EL) devices were fabricated with the structure as follows: indium tin oxide (ITO)/hole transport layer (HTL) NPB or MTCD/emitter layer M[RE(beta-diketonate)(4)] complexes)/Aluminum (Al). All the films were deposited by thermal evaporation carried out in a high vacuum environment system. The OLED light emission was independent of driving voltage, indicating that the combination of charge carriers generates excitons within the M[RE(beta-diketonate)(4)] layers, and the energy is efficiently transferred to RE(3+) ion. As a best result, a pure red and green electroluminescent emission was observed from the Eu(3+) and Tb(3+) devices, confirmed by (X,Y) color coordinates. (C) 2008 Elsevier B.V. All rights reserved.

Synthesis, characterization and spectroscopic investigation of new tetrakis(acetylacetonato)thulate(III) complexes containing alkaline metals as countercations

In this work a series of tetrakis complexes C[Tm(acac)(4)] where C(+) = Li(+) Na(+) and K(+) countercations and acac = acetylacetonate ligand were synthesized and characterized for photoluminescence investigation The relevant aspect is that these complexes are water-free in the first coordination sphere The emission spectra of the tetrakis Tm(3+)-complexes present narrow bands characteristic of the (1)G(4)->(3)H(6) (479 nm) (1)G(4)->(3)F(4) (650 nm) and (1)G(4) ->(3)H(5) (779 nm) transitions of the Tm(3+) ion with the blue emission color at 479 nm as the most prominent one The lifetime values (tau) of the emitting (1)G(4) level of the C[Tm(acac)(4)] complexes were 344 360 and 400 ns for the Li(+) Na(+) and K(+) countercations respectively showing an increasing linear behavior versus the ionic radius of the alkaline ion An efficient intramolecular energy transfer process from the triplet state (T) of the ligands to the emitting (1)G(4) state of the Tm(3+) ion is observed This fact together with the absence of water molecules in first coordination sphere allows these tetrakis Tm(3+)-complexes to act as efficient blue light conversion molecular devices (c) 2010 Elsevier B V All rights reserved

An insight into the beginning stage of the aqueous ring opening metathesis polymerization of exo,exo-7-oxabicyclo[2.2.1]hept-5-ene-2,3-dicarboxylic acid with Ru(III) compounds: the consumption of Ru(III) species in the presence of carboxylic acids monitored by ESR spectroscopy

The presence of paramagnetic species in the aqueous ring opening metathesis polymerizations of the exo,exo-7-oxabicyclo[2.2.1]hept-5-ene-2,3-dicarboxylic acid monomer with RuCl(3) and K(2)[RuCl(5)H(2)O] compounds was studied using ESR techniques. It was observed that the intensities of the Ru(III) signals in the ESR spectra decrease on the time scale of the induction period so that the ROMP can take place. The intensity of the Ru(III) signal almost disappeared 50 min after reacting with K(2)[RuCl(5)H(2)O] and after 100 mm in the case of RuCl(3). Reactions of the cis-[Ru(NH(3))(4)(H(2)O)(2)](tfms)(3) and [Ru(NH(3))(5)H(2)O](tfms)(3) complexes with the monomer and different organic compounds representing the organic functions in the monomer (furan, norbornene, but-2-ene-1,4-diol and formic, acetic, oxalic and maleic acids) were also monitored by ESR and UV/vis spectra. It was deduced that the organic acids provide the disappearance of the Ru(III) signal. The proton NMR relaxation times of the residual water in D(2)O for reactions with oxalic acid suggested that the presence of paramagnetic ions in the solution decreases along with

Light-Induced Structural Change in Iridium Complexes Studied by Electron Spin Resonance

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Bioactivity of pyridine-2-thiolato-1-oxide metal complexes: Bi(III), Fe(III) and Ga(III) complexes as potent anti-Mycobacterium tuberculosis prospective agents

In the search for new therapeutic tools against tuberculosis and to further address the therapeutic potential of pyridine-2-thiol 1-oxide (Hmpo) metal complexes, two new octahedral [M(III)(mpo)3] complexes, with M = Ga or Bi, were synthesized and characterized in the solid state and in solution. Attempts to crystallize [Ga(III)(mpo)3] in CH2Cl2 led to single crystals of the reaction product [GaCl(mpo)2], where the gallium(III) ion is in a square basis pyramidal environment, trans-coordinated at the basis to two pyridine-2-thiolato 1-oxide anions acting as bidentate ligands through their oxygen and sulfur atoms. The biological activity of the new [M(III)(mpo)3] complexes together with that of the previously reported Fe(III) analogous compound and the pyridine-2-thiol 1-oxide sodium salt (Na mpo) was evaluated on Mycobacterium tuberculosis. The compounds showed excellent activity, both in the standard strain H37Rv ATCC 27294 (pan-susceptible) and in five clinical isolates that are resistant to the standard first-line anti-tuberculosis drugs isoniazid and rifampicin. These pyridine-2-thiol 1-oxide derivatives are promising compounds for the treatment of resistant tuberculosis.

Neurotrophic factors and their receptors

Four GDNF ligands (GDNF, neurturin, artemin and persephin), and mesencephalic astrocyte-derived neurotrophic factor (MANF) and conserved dopamine neurotrophic factor (CDNF) protect midbrain dopaminergic neurons that degenerate in Parkinson's disease. Each GDNF ligand binds a specific coreceptor GDNF family receptor α (GFRα), leading to the formation of a heterotetramer complex, which then interacts with receptor tyrosine kinase RET, the signalling receptor. The present thesis describes the structural and biochemical characterization of the GDNF2-GFRα12 complex and the MANF and CDNF proteins. Previous and current mutation data and comparison between GDNF-GFRα1 and artemin-GFRα3 binding interfaces show that N162GFRα1, I175GFRα1, V230GFRα1, Y120GDNF and L114GDNF are the specificity determinants among different ligand-coreceptor pairs. The structure suggests that sucrose octasulphate, a heparin mimic, interacts with a region R190-K202 within domain 2 of GFRα1. Mutating these residues on the GFRα1 surface, which are not in the GDNF binding region, affected RET phosphorylation, which provides a putative RET binding region in domain 2 and 3 of GFRα1. The structural comparison of the GDNF-GFRα1 and artemin-GFRα3 complexes shows a difference in bend angle between the ligand monomers. This variation in bend angle of the ligand may affect the kinetics of RET phosphorylation. To confirm that the difference is not due to crystallization artefacts, I crystallized the GDNF-GFRα1 complex without SOS in different cell dimensions. The structure of the second GDNF-GFRα1 complex is very similar to the previous one, suggesting that the difference between the artemin-GFRα3 and GDNF-GFRα1 complexes are intrinsic, not due to crystal packing. Finally, MANF and CDNF are bifunctional proteins with extracellular neurotrophic activity and ER resident cytoprotective role. The crystal structures of MANF and CDNF are presented here. Intriguingly, the structures of both the neurotrophic factors do not show structural similarity to any of previously known growth factor superfamilies; instead they are similar to saposins, the lipid-binding proteins. The N-terminal domain of MANF and CDNF contain conserved lysines and arginines on its surface, which may interact with negatively charged head groups of phospholipids, as saposins do. Thus MANF and CDNF may provide neurotrophic activities by interacting with a lipo-receptor. The structure of MANF shows a CXXC motif forming internal disulphide bridge in the natively unfolded C-terminus. This motif is common to reductases and disulphide isomerases. It is thus tempting to speculate that the CXXC motif of MANF and CDNF may be involved in oxidative protein folding, which may explain its cytoprotective role in the ER.

Photobiomodulation by Low Power Laser Irradiation Involves Activation of Latent TGF-β1

Laser mediated stimulation of biological process was amongst its very first effects documented by Mester et al. but the ambiguous and tissue-cell context specific biological effects of laser radiation is now termed ‘Photobiomodulation’. We found many parallels between the reported biological effects of lasers and a multiface-ted growth factor, Transforming Growth Factor-β (TGF-β). This review outlines the interestingparallelsbetween the twofieldsand our rationalefor pursuingtheir potential causal correlation. We explored this correlation using an in vitro assay systems and a human clinical trial on healing wound extraction sockets that we reported in a recent publication. In conclusion we report that low power laser irradiation can activate latent TGF-β1 and β3 complexes and suggest that this might be one of the major modes of the photobiomodulatory effects of low power lasers.

Highly luminescent and thermally stable lanthanide coordination polymers designed from 4-(dipyridin-2-yl)aminobenzoate: efficient energy transfer from Tb3+ to Eu3+ in a mixed lanthanide coordination compound

Herein, a new aromatic carboxylate ligand, namely, 4-(dipyridin-2-yl)aminobenzoic acid (HL), has been designed and employed for the construction of a series of lanthanide complexes (Eu3+ = 1, Tb3+ = 2, and Gd3+ = 3). Complexes of 1 and 2 were structurally authenticated by single-crystal X-ray diffraction and were found to exist as infinite 1D coordination polymers with the general formulas {Eu(L)(3)(H2O)(2)]}(n) (1) and {Tb(L)(3)(H2O)]center dot(H2O)}(n) (2). Both compounds crystallize in monoclinic space group C2/c. The photophysical properties demonstrated that the developed 4-(dipyridin-2-yl)aminobenzoate ligand is well suited for the sensitization of Tb3+ emission (Phi(overall) = 64%) thanks to the favorable position of the triplet state ((3)pi pi*) of the ligand the energy difference between the triplet state of the ligand and the excited state of Tb3+ (Delta E) = (3)pi pi* - D-5(4) = 3197 cm(-1)], as investigated in the Gd3+ complex. On the other hand, the corresponding Eu3+ complex shows weak luminescence efficiency (Phi(overall) = 7%) due to poor matching of the triplet state of the ligand with that of the emissive excited states of the metal ion (Delta E = (3)pi pi* - D-5(0) = 6447 cm(-1)). Furthermore, in the present work, a mixed lanthanide system featuring Eu3+ and Tb3+ ions with the general formula {Eu0.5Tb0.5(L)(3)(H2O)(2)]}(n) (4) was also synthesized, and the luminescent properties were evaluated and compared with those of the analogous single-lanthanide-ion systems (1 and 2). The lifetime measurements for 4 strongly support the premise that efficient energy transfer occurs between Tb3+ and Eu3+ in a mixed lanthanide system (eta = 86%).

Rab9A is required for delivery of cargo from recycling endosomes to melanosomes

Melanosomes are a type of lysosome-related organelle that is commonly defective in Hermansky-Pudlak syndrome. Biogenesis of melanosomes is regulated by BLOC-1, -2, -3, or AP-1, -3 complexes, which mediate cargo transport from recycling endosomes to melanosomes. Although several Rab GTPases have been shown to regulate these trafficking steps, the precise role of Rab9A remains unknown. Here, we found that a cohort of Rab9A associates with the melanosomes and its knockdown in melanocytes results in hypopigmented melanosomes due to mistargeting of melanosomal proteins to lysosomes. In addition, the Rab9A-depletion phenotype resembles Rab38/ 32-inactivated or BLOC-3-deficient melanocytes, suggesting that Rab9A works in line with BLOC-3 and Rab38/ 32 during melanosome cargo transport. Furthermore, silencing of Rab9A, Rab38/ 32 or its effector VARP, or BLOC-3-deficiency in melanocytes decreased the length of STX13-positive recycling endosomal tubules and targeted the SNARE to lysosomes. This result indicates a defect in directing recycling endosomal tubules to melanosomes. Thus, Rab9A and its co-regulatory GTPases control STX13-mediated cargo delivery to maturing melanosomes.

Syntheses and crystal structures of bis(tetrahydrofurfurylindenyl) lanthanocene chlorides (C4H7OCH2C9H6)(2)LnCl (Ln = La, Lu)

Reaction of two equivalents of tetrahydrofurfuryl indenyl lithium with anhydrous lanthanide trichlorides in THF afforded bis(tetrahydrofurfurylindenyl) lanthanide chlorides (C4H7OCH2C9H6)(2)LnCl, Ln=La(l), Pr(2), Lu(3). Complexes I and 3 are characterized by single-crystal analysis. The results of crystal structural determination reveal that they are 9-coordinate monomeric intramolecular complexes with a trans arrangement of both the sidearms and indenyl rings in the solid state. The effects of rare earth ionic radii on the structures Of (C4H7OCH2C9H6)(2)LnCl are discussed.

A novel way to enhance electroluminescence performance based on soluble binary and ternary europium 1,1,1-trifluoroacetylacetonate

Five rare earth complexes (Gd(acae)(3), Gd(TFacaC)(3), Eu(acaC)(3), Eu(TFacaC)(3) and Eu(TFacaC)(3)bipy; acac, acetylacetone; TFacac, 1,1,1-trifluoroacetylacetone; bipy, 2,2'-bipyridyl) were synthesized. By comparing the phosphorescence spectra of Gd(acac)(3) and Gd(TFacac)(3) the effect of the replacement of hydrogen by fluorine was examined. Organic light-emitting devices (OLEDs) based on the corresponding europium complexes as emissive layers were also fabricated by the spin-coating method. The triple-layer-type device with the structure glass substrate/ITO (indium-tin oxide)/PVK [poly(N-vinylcarbazole)]/(PVKEu)-Eu-.(TFacac)(3)bipy:PBD[2-(4-bibipyyl)-5-(4-t-butylbipyl-1,3,4-oxadiazole)]/PBD/Al (aluminum) exhibits a brighter red luminescence than those devices with Eu(acac)(3) and Eu(TFacac)(3) complexes as emissive centers upon applying a d.c. voltage.

Near infrared electroluminescence from neodymium complex-doped polymer light emitting diodes

Organic light emitting diode devices employing organometallic Nd(9-hydroxyphenalen-1-one)(3) complexes as near infrared emissive dopants dispersed within poly(N-vinylcarbazole) (PVK) host matrices have been fabricated by spin-casting layers of the doped polymer onto glass/indium tin oxide (ITO)/3,4-polyethylene-dioxythiophene-polystyrene sulfonate (PEDOT) substrates. Room temperature electroluminescence, centered at similar to 1065 nm. was observed from devices top contacted by evaporated aluminum or calcium metal cathodes and was assigned to transitions between the F-4(3/2) -> I-4(11/2) levels of the Nd3+ ions. In particular, a near infrared irradiance of 8.5 nW/mm(2) and an external quantum efficiency of 0.007% was achieved using glass/ITO/PEDOT/PVK:Nd(9-hydroxyphenalen-1-one)(3)/Ca/Al devices. (c) 2005 Elsevier B.V. All rights reserved.

Caractérisation biochimique du complexe Smc5-6

Les membres de la famille SMC (Structural Maintenance of Chromosomes), présents dans tous les domaines de la vie, sont impliqués dans des processus allant de la cohésion des chromatides-sœurs jusqu’à la réparation de l’ADN. Chacun des membres de cette famille, composée de 6 membres (Smc1 à Smc6), s’associe avec un autre membre ainsi qu’à des sous-unités non-SMC pour former 3 complexes : cohésine, condensine et Smc5-6. L’implication du complexe Smc5-6 dans plusieurs aspects du maintien de l’intégrité génomique est bien démontrée. Néanmoins, une question fondamentale concernant ce complexe demeure encore sans réponse: comment peut-il être impliqué dans autant d’aspects de la vie d’une cellule? Encore à ce jour, il est difficile de répondre à cette question en raison du manque d’information disponible au sujet des activités biochimiques de ce complexe. C’est pourquoi l’objectif de ce travail consiste en la caractérisation biochimique du complexe Smc5-6. La biochimie de cohésine et condensine suggère diverses possibilités en ce qui a trait aux activités biochimiques du complexe Smc5-6. La première étape de mon projet fut donc d’élaborer une procédure pour la purification de Smc5 et Smc6 après surexpression en levure. Après plusieurs expériences, il apparut clair que les deux protéines possèdent une activité de liaison à l’ADN simple brin (ADNsb) ainsi qu’à l’ADN double brins (ADNdb) et que, même si les protéines peuvent se lier aux deux types d’ADN, elles possèdent une plus grande affinité pour l’ADNsb. De plus, ces expériences permirent de démontrer que l’interaction entre Smc5 ou Smc6 et l’ADNsb est très stable, alors que l’interaction avec l’ADNdb ne l’est pas. Suite à l’obtention de ces résultats, la seconde étape fut la détermination de la ou des partie(s) de Smc5 et Smc6 permettant la liaison à l’ADN. Pour répondre à cette question, une dissection moléculaire fut réalisée, suivi d’une caractérisation des différents domaines constituants Smc5 et Smc6. De cette façon, il fut possible de démontrer qu’il existe deux sites de liaison à l’ADN sur Smc5 et Smc6 ; le premier site se trouvant dans le domaine «hinge» ainsi que dans la région adjacente du domaine «coiled-coil» et le second au niveau de la tête ATPase des deux protéines. Bien que les deux domaines puissent lier l’ADNsb, il fut démontré qu’une différence majeure existe au niveau de leur affinité pour ce type d’ADN. En effet, le domaine «hinge» possède une affinité plus forte pour l’ADNsb que la tête ATPase. De plus, cette dernière est incapable de lier l’ADNdb alors que le domaine «hinge» le peut. L’identification des sites de liaison à l’ADN sur Smc5 et Smc6 permettra de créer de nouveaux mutants possédant un défaut dans la liaison à l’ADN. Ainsi, l’étude du complexe Smc5-6 durant la réparation de l’ADN in vivo sera facilité.

The interplay of secondary Hg⋯S, Hg⋯N and Hg⋯π bonding interactions in supramolecular structures of phenylmercury(ii) dithiocarbamates

Three new phenylmercury(II) and one mercury(II) dithiocarbamate complexes viz. PhHg S2CN(PyCH2) Bz (1), PhHg S2CN(PyCH2)CH3 (2), PhHg S2CN(Bz)CH3 (3), and [Hg (NCS2(PyCH2)Bz)(2)] (4) (Py = pyridine; Bz = benzyl) have been synthesized and characterized by elemental analyses, IR, electronic absorption, H-1 and C-13 NMR spectroscopy. The crystal structures of 1, 2 and 3 showed a linear S-Hg-C core at the centre of the molecule, in which the metal atom is bound to the sulfur atom of the dithiocarbamate ligand and a carbon atom of the aromatic ring. In contrast the crystal structure of 4 showed a linear S-Hg-S core at the Hg(II) centre of the molecule. Weak intermolecular Hg center dot center dot center dot N (Py) interactions link molecules into a linear chain in the case of 1, whereas chains of dimers are formed in 2 through intermolecular Hg center dot center dot center dot N (Py) and Hg center dot center dot center dot S interactions. 3 forms a conventional face-to-edge dimeric structure through intermolecular Hg center dot center dot center dot S secondary bonding and 4 forms a linear chain of dimers through face-to-face Hg center dot center dot center dot S secondary bonding. In order to elucidate the nature of these secondary bonding interactions and the electronic absorption spectra of the complexes, ab initio quantum chemical calculations at the MP2 level and density functional theory calculations were carried out for 1-3. Complexes 1 and 2 exhibited photoluminescent properties in the solid state as well as in the solution phase. Studies indicate that Hg center dot center dot center dot S interactions decrease and Hg center dot center dot center dot N interactions increase the chances of photoluminescence in the solid phase

Thionicotinamide SAM on Gold: Adsorption Studies and Electroactivity

STM and impedance results of the self-assembled monolayer (SAM) formed with thionicotinamide (TNA) on gold indicate the presence of defects that increase with the immersion time of the electrode in the TNA solution affecting the SAM electroactivity toward the electron transfer reaction of the cytochrome e metalloprotein and [Fe(CN)(6)](4-) and [Ru(NH(3))(6)](3+) complexes. It was observed that this electroactivity was also affected by the pH of the electrolyte solution. SERS and STM data indicate sulfur coordination to the surface with contribution of the NH(2) group. From the dependence of the TNA surface coverage on the temperature and concentration in solution, thermodynamic parameters of adsorption were determined.