Gold phosphide complexes

6 pages, 9 schemes, 6 figures.The vast majority of gold complexes with five group-element donor ligands contain tertiary phosphines, although compounds with amine, arsine or stibine ligands are also known. Although phosphide ligands, which are formed by deprotonation of non-tertiary phosphines, are closely related to the former, they have been employed to a lesser extent, mainly due to their lower stability. Thus, the chemistry of phosphido-bridged derivatives of the main group elements1-3 or transition metals4-6 has been a matter of interest for various research groups in the last few years. While there are many phosphido complexes with metals, mainly of groups 67-12 or 10,13-20 the chemistry of gold derivatives has experienced less progress in this field of research in spite of the possible catalytic behaviour of di- and polynuclear phosphido-bridged compounds.21 This is an interesting field of research, because the substitution of one or more protons by metal atoms allows the synthesis of homo- or hetero-polynuclear compounds in which the presence of a small bridging atom, such as phosphorus, may give rise to intermetallic contacts, which, as is known, are often responsible for surprising and interesting optical properties, such as luminescence, area with an increasing importance in the last years. This review focuses on gold phospide complexes derived from secondary phosphines (PR2H), primary phosphines (PRH2), primary diphosphines (PH2(CH2)nPH2) or from PH3. The moieties derived from all these complexes usually act as bridging ligands between more than one gold centre or between gold and other transition metal centres.Peer reviewe

Estudio de fatiga térmica de cermets base hierro

Ponencia presentada en: XI Congreso Nacional de Materiales Compuestos, celebrado los días 6, 7 y 8 de julio de 2015, en Móstoles (España).En el presente trabajo se analiza el comportamiento a fatiga térmica de materiales compuestos de matriz férrea y refuerzo de TiCN desde dos puntos de vista: la influencia de la temperatura máxima alcanzada durante la fatiga térmica y la influencia del número de ciclos de calentamiento y enfriamiento. Además, se compara el comportamiento de estos materiales con el de un acero de herramientas de uso convencional. Este estudio del comportamiento frente a cambios cíclicos de temperatura para ambos materiales se realiza en base a su resistencia a la oxidación y se compara con la oxidación estática que se produce a temperatura elevada constante. Para ello las probetas se han sometido a diferentes ciclos de fatiga térmica, alcanzando temperaturas máximas de 1000 ºC durante un máximo de 100 ciclos; posteriormente se ha caracterizado tanto su superficie como su sección transversal utilizando diferentes técnicas: medida de cambio de masa, DRX, SEM, EDX y microdureza.Los autores agradecen la financiación recibida para la realización de este trabajo al MINECO (proyecto MAT2012-38650-C02-01) y a la Comunidad de Madrid por el programa MULTIMAT-CHALLENGE, ref. S2013/MIT-2862Publicad

Synthesis, Photochemical, and Redox Properties of Gold(I) and Gold(III) Pincer Complexes Incorporating a 2,2′:6′,2″-Terpyridine Ligand Framework

Reaction of [Au(C6F5)(tht)] (tht = tetrahydrothiophene) with 2,2′:6′,2″-terpyridine (terpy) leads to complex [Au(C6F5)(η1-terpy)] (1). The chemical oxidation of complex (1) with 2 equiv of [N(C6H4Br-4)3](PF6) or using electrosynthetic techniques affords the Au(III) complex [Au(C6F5)(η3-terpy)](PF6)2 (2). The X-ray diffraction study of complex 2 reveals that the terpyridine acts as tridentate chelate ligand, which leads to a slightly distorted square-planar geometry. Complex 1 displays fluorescence in the solid state at 77 K due to a metal (gold) to ligand (terpy) charge transfer transition, whereas complex 2 displays fluorescence in acetonitrile due to excimer or exciplex formation. Time-dependent density functional theory calculations match the experimental absorption spectra of the synthesized complexes. In order to further probe the frontier orbitals of both complexes and study their redox behavior, each compound was separately characterized using cyclic voltammetry. The bulk electrolysis of a solution of complex 1 was analyzed by spectroscopic methods confirming the electrochemical synthesis of complex 2

1,4-Bis(2′-pyridylethynyl)benzene as a ligand in heteronuclear gold–thallium complexes. Influence of the ancillary ligands on their optical properties

The reaction of 1,4-bis(2′-pyridylethynyl)benzene (L) with [{Au(C6X5)2}Tl]n affords new heterometallic AuI/TlI complexes with different stoichiometries, structural arrangements and optical properties depending on the halogens present in the aryl group. The chlorinated derivative [{Au(C6Cl5)2}Tl(L)]n (1) displays polymeric chains built thanks to unsupported Au⋯Tl interactions and bridging bidentate ligands between adjacent chains, while in the fluorinated species [{Au(C6F5)2}2Tl2(L)2]n (2), also containing N-donor bridging ligands and Au⋯Tl contacts, polymerization occurs via Tl⋯Caryl non-bonding interactions between neighbouring molecules. The optical properties of 1 and 2 have been studied experimentally and theoretically, concluding that the luminescence of 1 in the solid state has its origin in the Au⋯Tl interactions, and that the Tl⋯Caryl interactions in 2 favour a non-radiative deactivation pathway that avoids luminescence. The strength of the non-bonding interactions present in 1 has also been theoretically studied at the HF and MP2 levels, revealing the metallophilic contact as the strongest one.This work was supported by the D.G.I. (MEC)/FEDER (CTQ2013-48635-C2-2-P).Peer reviewe

Polarized supramolecular aggregates based on luminescent perhalogenated gold derivatives

Reaction of [Au(C6F5)(tht)] (tht = tetrahydrothiophene) with 1,3,5-triaza-7-phosphaadamantane (PTA) and 3,7-diacetyl-1,3,7-triaza-5-phosphabicyclo[3.3.1]-nonane (DAPTA) leads to the formation of [Au(C6F5)(phosph)] (phosph = PTA, 1; phosph = DAPTA, 2). The compounds are slightly soluble in water and aggregate at higher concentrations giving rise to the formation of needle- and rod-like structures (1) and well-organized spherical aggregates (2). Compounds 1 and 2 were reacted with AgPF6 giving rise to the formation in all cases of luminescent water soluble 1:1 Au·Ag heterometallic complexes, as evidenced by X-ray crystal structure determination. The use of different silver salts that differ on the counterion induces changes on the resulting luminescence and aggregation morphology

Perhalophenyl Three-Coordinate Gold(I) Complexes as TADF Emitters : A Photophysical Study from Experimental and Computational Viewpoints

We report the synthesis of novel perhalophenyl three- coordinated gold( I) complexes using 1,2- bis-(diphenylphosphino)benzene (dppBz) as the chelating ligand and [AuR(tht)] (R = C6F5, C6Cl2F3, C6Cl5) as the perhalophenyl-gold(I) source, leading to [AuR(dppBz)] (R = C6F5 (1), C6Cl2F3 (2), C6Cl5 (3)) complexes. The solid-state structures of compounds 2 and 3 consist of discrete three-coordinated Au(I) complexes, which show a distorted trigonal planar geometry for the gold center with dissimilar Au-P distances. The distorted structural arrangement is closely related to its photophysical properties. The studied complexes display very intense emissions at room temperature (RT) and at 77 K in the solid state. Studies of the emissive properties of the complexes at different temperatures suggest that the emissions are phosphorescent at 77 K and exhibit thermally activated delayed fluorescence (TADF) at RT. First-principle calculations of the photophysical processes yielded rate constants for intersystem crossing and reverse intersystem crossing that are in excellent agreement with experimental data.Peer reviewe

Experimental and theoretical evidence of the first Au(I)Bi(III) interaction

3 pages, 3 figures, 1 scheme.-- Published as an advance article on the web 15th Nov. 2006.Complex [Au(C6F5)2][Bi(C6H4CH2NMe2-2)2] 1 displays the first example of an interaction between Au(I) and Bi(III), the nature of which is shown to be consistent with the presence of a high ionic contribution (79%) and a dispersion type (van der Waals) interaction (21%).The D.G.I.(MEC)/FEDER (CTQ2004-05495) project is acknowledged. M. Monge thanks the MEC-UR for his contract ‘‘Ramón y Cajal’’. EC through the Socrates/Erasmus program (M. Nema) and a NATO research fellowship (C. Silvestru) are also acknowledged.Peer reviewe

Silver-based terpyridine complexes as antitumor agents

Silver complexes bearing substituted terpyridine or tetra-2-pyridinylpyrazine ligands have been prepared and structurally characterised. The study of the anticancer properties of silver complexes with this type of ligands is scarce, despite the possibilities of combining the properties of the metal and the ability of the ligands for DNA binding. Here, the antiproliferative activity, stability, CT-DNA binding and mechanism of cell death of these types of derivatives are studied. High cytotoxicity against different tumour cells was observed, and, more important, a great selectivity index has been detected between tumour cells and healthy Lymphocytes T for some of these compounds. The CT-DNA interaction study has shown that these derivatives are be able to interact with CT-DNA via moderate intercalation. Furthermore, cell death studies indicate that these derivatives promote the apoptosis via mitochondrial pathway

Mini AuAg Wavy Nanorods Displaying Plasmon-Induced Photothermal and Photocatalytic Properties

Alloyed AuAg wavy nanorods (wNRs) of approximate to 24.0 nm length and 3.5 nm width are formed by the mild decomposition of the organometallic complex [Au2Ag2(C6F5)(4)(OEt2)(2)](n) in tetrahydrofuran (THF) in the presence of oleic acid. Ligand exchange with l-glutathione (GSH) or poly(ethylene glycol) methyl ether thiol (PEG-SH) leads to water-soluble nanostructures. These AuAg wNRs display tunable size-dependent longitudinal localized surface plasmon resonance (l-LSPR) broad absorptions beyond 750 nm in the near-infrared (NIR) I and II regions. These intense plasmonic absorptions lead to interesting photothermal, catalytic, and photocatalytic properties, including the catalytic reduction of 4-nitrophenol, the photocatalytic reduction of 4-nitrostyrene, or the photocatalytic dehydrogenation of ammonia borane for H-2 release