1,720,959 research outputs found
Novel rhenium(V) oxo complexes containing bis(pyrazol-1-yl)acetate and bis(pyrazol-1-yl) sulfonate as tripodal N,N,O-heteroscorpionate ligands
No full textReactions of [NBU4][Re(O)Cl-4] with bis(pyrazol-1-yl) methane (bpzm) and bis(pyrazol-1-yl)acetate (Hbpza) and with the lithium salts lithium [bis(3,5-dimethylpyrazol-1-yl)acetate] (Libdmpza) and lithium [bis(3,5-dimethylpyrazol-1-yl)methanesulfonate] (Libdmpzs) produce a series of new compounds containing either a kappa(2)-N,N bidentate pyrazolyl ligand [Re(O)(bpzM)Cl-3 (1), Re(O)(bpzm)(OMe)Cl-2 (2), Re(O)(bpzaOMe)(OMe)Cl-2 (4)] or a kappa(3)-N,N,O heteroscorpionate [Re(O)(bpza)Cl-2 (3), Re(O)(bdmpza)Cl-2 isomers 5 and 6, Re(O)(bdmpza)(OMe)Cl (7), Re(O)(bdmpza)(OEt)Cl (8), Re(O)(bdmpzs)(OMe)Cl (9), Re(O)(bdmpzs)(OEt)Cl (10)]. X-ray analyses of 1 and 3 show in both cases a distorted octahedral environment around the rhenium atom. The nature and the geometry of the products are strongly determined by the reaction solvent and by the heteroscorpionate ligand itself. When scorpionates bear methylated pyrazolyl rings mixed heterocomplexes Re(O) (bdmpza) (glycol) (11) and Re(O)(bdmpzs)(glycol) (12) are obtained (H(2)glycol = ethylene glycol). Also 11 shows an octahedral geometry as assessed by X-ray study
Novel scorpionate-type triscarbene ligands and their silver and gold complexes
No full textNew silver(I) carbene complexes were obtained starting from the N-heterocyclic carbene ligand precursors {[HB(RImH)(3)]Br(2)} (R = Bn, Mes and t-Bu) and {[HC(MeBImH)(3)](BF(4))(3)}, by treatment of the imidazolium salt with Ag(2)O. Use of the tris-imidazolylborate precursors resulted in stable, well-characterized trimetallic complexes of general formula {Ag(3)[HB(RIm)(3)](2)}Br, which were successfully employed as carbene transfer reagents in the synthesis of related gold(I) complexes by transmetallation. The silver complexes also proved to be active catalysts of the coupling of aryl iodides with terminal alkynes (the Sonogashira reaction), although related bimetallic silver complexes were found to exhibit enhanced reactivity
Synthesis and characterization of divalent metal complexes containing the heteroscorplonate ligand dihydrobis(3-carboxyethyl-5-methylpyrazolyl)borate
No full textThe dihydrobis(3-carboxyethyl-5-methylpyrazolyl)borate ligand, Bp(COOET,Me), reacts with divalent metals to yield complexes of general type [(Bp(COOET,Me))(2)M], where M = Mn(II), Fe(II), Co(II), Ni(II), Zn(II), Cu(II), Pb(II) and Cd(II). All complexes have been fully characterized by elemental analyses and FT-IR in the solid state and by NMR (H-1 and Cd-113 NMR) spectroscopy and electrospray ionization mass spectrometry in solution. A single crystal structural characterization is reported for [Cu(Bp(COOET,Me))(2)] and [Zn(Bp(COOET,Me))(2)]. In the two complexes, both metals are four-coordinated and they are only bound to the nitrogen atoms of the bis(pyrazolyl)borate ligand; however, while the environment of the copper atom is square planar, that of the zinc center shows a tetrahedral distorted conformation
Oxo-rhenium(V) compounds bis(3,5-dimethylpyrazol-1-yl)acetate containing scorpionate ligand
No full textLigand-exchange reactions of bidentate donor agents such as malonic acid (H(2)mal) or 1,3-propanediol (H(2)diol) with labile Re(O)(bdmpza)Cl-2 (bdmpza = bis(3,5-dimethylpyrazol-1-yl)acetate) precursors in the presence of triethylamine yield the mixed-ligand complexes Re(O)(bdmpza)(mal) (2) and Re(O)(bdmpza)(diol) (3), respectively. Compounds 2 and 3 can also be obtained starting directly from [Re(O)Cl-4][NBu4], Libdmpza and the appropriate bidentate ligand in the presence of triethylamine. X-ray analyses of the two compounds show in both cases a distorted octahedral geometry around the rhenium atom comprising two pyrazolyl nitrogens and the bidentate ligand in the equatorial plane, and the oxo and the carboxylate oxygens on the apices. Differently from 2 and 3, X-ray diffraction analysis of the asymmetric precursor (OC-6-42)Re(O)(bdmpza)Cl-2 (1) reveals a slightly distorted octahedral geometry with the apical positions taken by the carboxylate oxygen and a chloride atom, and with the equatorial plane occupied by the nitrogens of the bis-pyrazolyl ligand, a chloride and the oxygen atom
New homoleptic carbene transfer ligands and related coinage metal complexes
No full textThe synthesis, spectroscopic and structural characterization of the carbene ligand precursor bis(4-benzyl-1,2,4-triazol-4-ium-1-yl)dihydroborate has been described. Treatment with Ag(2)O leads to the silver(I) complex of the new monoanionic bis(4-benzyl-1,2,4-triazol-5-ylidene-1-yl)dihydroborate dicarbene ligand. The resulting dimetallacycle carbene complex has been used to synthesize the homoleptic gold(I) complex by transmetallation reaction
Synthesis, characterization and in vitro antitumor properties of tris(hydroxymethyl)phosphine copper(I) and silver(I) complexes
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Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
In vitro antitumor activity of the water soluble copper(I) complexes bearing the tris(hydroxymethyl)phosphine ligand
No full textMonocationic hydrophilic complexes [Cu(thp)4](+) 3 and [Cu(bhpe)2](+) 4 were synthesized by ligand exchange reactions starting from the labile [Cu(CH3CN)4][PF6] precursor in the presence of an excess of the relevant hydrophilic phosphine. Complexes 3 and 4 were tested against a panel of several human tumor cell lines. Complex 3 has been shown to be about 1 order of magnitude more cytotoxic than cisplatin. Chemosensitivity tests performed on cisplatin and multidrug resistance phenotypes suggested that complex 3 acts via a different mechanism of action than the reference drug. Different short-term proliferation assays suggested that lysosomal damage is an early cellular event associated with complex 3 cytotoxicity, probably mediated by an increased production of reactive oxygen species. Cytological stains and flow cytometric analyses indicated that the phosphine copper(I) complex is able to inhibit the growth of tumor cells via G2/M cell cycle arrest and paraptosis accompanied with the loss of mitochondrial transmembrane potential
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
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