1,721,010 research outputs found
Synthesis and biological evaluation of new [Tc-99m(III)( PS)(2)(L)] mixed-ligand compounds (PS= phosphino-thiolate; L=dithiocarbamate), useful in design and development of Tc(III)radiopharmaceuticals
No full textA new phase of bis[2-(diphenylphosphino-κP)phenylazanido-κN](ethanolato)(oxo)rhenium(V)
No full textThe title compound, [Re(C18H15NP)2(C2H5O)O], was synthesized by the oxidation-substitution reaction of [Re(III)(PNH)2(PNH2)]Cl, where PNH2 is 2-(diphenylphosphino)phenylamine, with NEt3 in EtOH. The X-ray diffraction study of this new triclinic phase, designated beta, confirms the molecular structural details for the monoclinic a isomer, which crystallized in space group P2(1)/c with a = 12.056 (3), b = 26.303 (6), c = 11.005 (3) angstrom, beta = 102.32 (2)-degrees [Refosco, Tisato, Bandoli, Bolzati, Dolmella, Moresco & Nicolini (1993). J. Chem. Soc. Dalton Trans. pp. 605-618]
Uncommon Anionic Dioxorhenium(V) and Neutral Monooxorhenium(V) Mixed-Ligand Complexes Containing Heterofunctionalized Phosphine Ligands: Syntheses and Structural Characterization
No full textThe potentially bidentate hybrid ligand (o-hydroxyphenyl)diphenylphosphine, abbreviated POH, reacted via ligand-exchange with pentavalent rhenium precursors to give a series of six-coordinate mono- and dioxo complexes. Accurate control of the metal:ligand stoichiometric ratio allowed for the isolation of the mono-substituted [ReOCl3(PO)](-) (1) and [ReOCl2(PO)(PPh(3))] (2) derivatives. 1 was found to be the key intermediate for the syntheses of three more types of bis-substituted compounds: anionic dioxo [ReO2(PO)(2)][A] (A = NBu(4) (3), AsPh(4) (4)), neutral monooxo [ReOX(PO)(2)] (X = Cl (5), Br (6), I (7)), and neutral monooxo mixed-ligand [ReOX(PO)(PNH)] [PNH = (o-amidophenyl)diphenylphosphine; X = Cl (8), Br (9), I (10)] complexes. In the monosubstituted complexes, the P,O-donors of the bidentate ligand spanned an equatorial (P) and the apical position (O) trans to the Re=O linkage in a distorted octahedral arrangement. In all of the bis-substituted monooxo compounds, the second chelate ligated on the equatorial plane almost orthogonally positioned with respect to the first one, the two phosphorus donors showing a mutual cis-(P,P) orientation. Dioxo complexes retained the cis(P,P) configuration with the bidentate ligands symmetrically coordinated on the equatorial plane normal to the trans-ReO2 core. All the complexes were characterized by various physical techniques, including IR, MS, and H-1/P-31{H-1} NMR. The X-ray structure of a representative compound for each category, namely [ReOCl3(PO)][NBu(4)] (1), [ReO2(PO)(2)][AsPh(4)] (4), [ReOCl(PO)(2)] (5), and [ReOCl(PO)(PNH)] (8), were determined. Crystals of 1 were monoclinic, P2(1)/n, a = 10.840(3) Angstrom, b = 22.167(6) Angstrom, c = 15.210(4) Angstrom, beta = 95.91(2)degrees, and Z = 4; those of 4 were triclinic, P (1) over bar, a = 12.679(7) Angstrom, b = 13.082(7) Angstrom, c = 19.649(8) Angstrom, alpha = 82.64(4) Angstrom, beta = 81.16(4)degrees, gamma = 62.27(3)degrees, and Z = 2; those of 5 were orthorhombic, a = 10.225(4) Angstrom, b = 14.208(6) Angstrom, c = 21.771(9) Angstrom, P2(1)2(1)2(1), and Z = 4; and those of 8 were orthorhombic, a = 10.199(2) Angstrom, b = 14.147(4) Angstrom, c = 21.772(6) Angstrom, P2(1)2(1)2(1), and Z = 4. The four structures were solved by the Patterson method and refined by full-matrix least-squares procedures to R = 0.050, 0.063, 0.043, and 0.039 for 1, 4, 5 and 8, respectively. Both solution state (P-31{H-1} NMR) and solid state (X-ray) demonstrated a cis-(P,P) arrangement for each bis-substituted complex, with the Re atom at the center of a highly distorted octahedron. Detailed analyses of the IR spectra of this series of Re(V) compounds in the region 900-580 cm(-1) allowed us the possibility to distinguish between symmetrical and asymmetrical bis-substituted complexes
Novel TcP3X3 (X=S, O) cores in Tc(III) chemistry
No full textIn recent years we devoted most of our research efforts in developing Tc chemistry with bidentate functionalized phosphines because of their ability to act both as reducing and coordinating agents [2]. These functionalized phosphines contain a P(III) atom that can easily reduce the pertechnetate ion and stabilize the metal in lower oxidation states by means of its pi-backbonding together with the chelation of the whole ligand. In this field encouraging results have been obtained with phosphino-carboxylic derivatives of the type Ph (R=o-C6H4, C2H4, CH2 (abbreviated as P-COOH) [3] and more recently with the ligand (2-diphenylphosphino)benzeneamine (abbr. PNH2 [4]. In both cases, Tc(III) complexes of the type Tc(P-X)3 (X=COO-, NH-) have been obtained, the three mono-negative bidentate ligands being coordi nated around the metal in a meridional configuration. The above mentioned ‘reducing-coordinating’ approach has allowed the synthesis of a class of Tc(III) complexes utilizing the tris(o-thiophenyl)phosphine, a tetradentate ‘umbrella shaped’ ligand. Either octahedral or trigonal bipyramidal geometries have been observed for the resulting complexes, depending on the con centration of the ancillary isonitrile ligand [5].In this context we now report on the reaction of pertechnetate with the two bidentate functionalized phosphines, (2-diphenylphosphino)thiophenol (abbr. P-SH) and (2-diphenylphosphino)phenol (abbr. P-OH) with the aim of looking at the molecular structure of the resulting complexes and to confirm the favourable reducing and coordinating properties of such a class of ligands towards technetium. The synthesis and characterization (including X-ray structure) of the resulting Tc(III)(P-S)3 (1) and Tc(III)(P-O)3 (2) complexes are reported here
Synthesis and NMR investigation on mer-[Re(III)Cl(3)(L)(3)] and mer-[Re(III)Cl(3)(L)(2)(PPh(3))] complexes (L = pyridine-like ligand). X-ray structure of mer-[Re(III)Cl(3)(3,5-lut)(3)]
No full textThe co-ordination geometry of the monomeric rhenium complexes mer-[Re(III)Cl(3)(L)(3)] (L = py 1,3,5-lut 2, 4-pic 3) has been determined in the solid state by single X-ray diffraction of the representative complex 2 and in solution by proton NMR spectroscopy. Only a single stable conformation has been found in the solid state and in solution, under the experimental conditions utilised. The NMR spectra of the related complexes mer-[Re(III)Cl(3)(L)(2)(PPh(3))] (L = py 4, 3,5-lut 5, 4-vinpy 6) have also been reported for comparison purposes. (C) 1998 Elsevier Science Ltd. All rights reserved
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
Synthesis, characterization and electrochemical studies on technetium(V) and rhenium(V) oxo-complexes with N,N′-2-hydroxypropane-1,3-bis(salicylideneimine)
No full textLigand-exchange reactions of potential quinquedentate Schiff base ligands derived from salicylaldehyde and 1,3-diamino-2-hydroxypropane (H3L) with [MOCl4]− (M = Tc and Re) have been investigated. The complexes [MOCl2(R-OH)(H2L·HCl)] (I) (R = Me, Et), [ReOCl(HL)] (II) and μ-O[MO(HL)]2 (III) were synthesized and characterized by the usual physicochemical measurements. Cyclic voltammetries for both III complexes reveal two separate and single-electron redox processes. The crystal structure of μ-O[TcO(HL)]2 was determined by single-crystal X-ray diffraction methods. Crystals are monoclinic, space group P21/c, with a = 9.423(6), b = 19.666(9), c = 22.785(11) Å, β = 99.41(4)° and Z = 4. X-ray diffraction provides 2842 observed reflections (up to θ = 40°) and the structure has been refined by full-matrix least-squares methods to R = 0.10. The ‘dimeric’ structure of μ-O[TcO(HL)]2 consists of two distorted octahedral TcO(HL) moieties bridged by an oxygen atom which occupies the sixth coordination site of each moiety with the Tc-O-Tc angle nearly linear (173°)
Copper(I) heteroleptic ‘3+1’ complexes: ligand effect on their in vitro cytotoxicity
No full textIn the last years we have focused our attention on copper(I) derivatives and due to the “soft” nature of Cu(I) the choice of ligands having soft donor atoms such phosphorous in tertiary phosphines or aromatic sp2 hybridized nitrogen of pyrazolyl derivatives, allowed us to obtain stable active derivatives. In particular, we have reported the synthesis of homoleptic phosphine copper(I) complexes and of heteroleptic copper(I) compounds comprising both phosphine and scorpionate ligands. They showed a remarkable in vitro cytotoxic activity also towards cisplatin sensitive and resistant cell lines suggesting a DNA-independent mechanism of action. By comparison of ‘2+1+1’ and ‘3+1’ complexes, the latter seemed by far the most active. For this reason we have prepared and screened a series of (3+1) [CuLP]0/+ copper(I) compounds containing a tridentate tris(azolyl)borate ligand (L) and an auxiliary monodentate phosphine (P), whose hydrophilicity and steric hindrance were systematically changed trying to find a structure-activity relationship.
Among them, [Cu(HB(pz)3)(PCN)] (HB(pz)3 = tris(pyrazolyl) borate, PCN = tris-cyanoethylphosphine) showed IC50 values up to 15-fold lower than those recorded with the reference metallodrug cisplatin. Mechanistic studies revealed that cancer cells treated with [Cu(HB(pz)3)(PCN)] died via a paraptotic cell death coherent with the impairment of cell proteolytic system. In vivo studies on syngeneic murine Lewis Lung Carcinoma (LLC) confirmed the antitumor efficacy of [Cu(HB(pz)3)(PCN)]
Co-ordination of (o-aminophenyl)diphenylphosphine in complexes containing the [MV=O]3+(M = Tc or Re) core
No full textReduction-substitution reactions of [TcO4]- with (o-aminophenyl)diphenylphosphine (HL) at a strictly controlled stoichiometric metal/ligand ratio gave neutral oxotechnetium(V) complexes of the type [TcOL2(OR)] (R = Me 1 or Et 2): Analogous [ReOL2(OR)] species (R = H 3, Me 4, Et 5, Pr 6, Bu 7, C2H4OH 8, C3H6OH 9, Ph 10 or OCMe 11) are instead produced via ligand-exchange reactions in basic media starting from (ReOCl4]-. Compounds 1-11 are referred to as 'equatorial' because the co-ordination of both bidentate L- chelates occurs symmetrically in the equatorial plane orthogonal to the M=O moiety, with a mutual cis-phosphorus configuration. The site trans to the oxo group is always occupied by an oxygen-containing monodentate ligand the co-ordination of which determines the stability of this class of octahedral complexes. Nevertheless the -OR group is easily exchangeable with other nucleophiles available in the reaction misture by the mass effect and/or donor ability of the incoming ligand. The crystal structures of complexes 1 and 5 have been determined: 1, monoclinic, space group P2(1)/c, Z = 4, a = 12.156(3), b = 26.005(6), c =1 0.953(2) angstrom, beta = 102.49(2)-degrees, R' 0.0611 using 1766 observed reflections; Tc-O(1) 1.700(8), Tc-O(2) 1.999(8), Tc-P 2.511(3) and 2.503(4), Tc-N 1.972(10) and 1.976(8) angstrom; O(1)-Tc-N 105.8(4) and 103.6(4), 0(l)-Tc-P 88.1(3) and 88.9(2), 0(l)-Tc-O(2) 158.3(3)-degrees; 5, monoclinic, space group P2(1)/c, Z = 4, a = 12.056(3), b 26.303(6), c = 11.005(3) angstrom, beta = 102.32(2)-degrees, R' 0.0614 using 4752 observed reflections; Re-O(1) 1.692(7), Re-O(2) 2.004(7), Re-P 2.495(2) and 2.493(3), Re-N 1.990(8) and 2.003(7) angstrom; O(1)-Re-N 104.6(3) and 102.6(3), O(1)-Re-P 89.1(2) and 88.8(2), 0(l)-Re-0(2) 160.8(3)-degrees. By treatment of [MOL,(OR)] solutions with HX (X = halide), further reduction to lower-oxidation-state species occurs when M = Tc, while another class of stable and neutral oxo complexes, termed 'twisted', is produced when M = Re. Two mutually orthogonal L- chelates co-ordinate the metal while still preserving the cis-phosphorus configuration, one ligand bridging an equatorial and an apical position (with the phosphinoamido nitrogen trans to the Re-O linkage) and the other two equatorial positions. The equatorial plane is completed by a halide atom. The chloro derivative [ReOL2Cl] exhibits two crystalline forms, alpha (12) and beta (13), the crystal structures of which have been determined: 12, monoclinic, space group P2(1)/n, Z = 4, a = 9.594(l), b =18.565(4), c = 17.656(2) angstrom, beta = 91.00(1)-degrees, R' 0.0477 using 2979 observed reflections; Re-0 1.767(7), Re-Cl 2.436(3), Re-P(1) 2.429(3), Re-P(2) 2.479(3), Re-N(1) 1.986(9), Re-N(2) 2.029(8) angstrom; O-Re-N(2) 162.8(3), O-Re-N(l) 108.6(3)-degrees; 13, orthorhombic, space group P2(1)2(1)2(1), Z = 4, a = 10.196(5), b = 14.047(6), c = 21.987(8) angstrom, R' 0.0671 using 2501 observed reflections; Re-0 1.69(l), Re-Cl 2.422(6), Re-P(1) 2.434(5), Re-P(2) 2.476(5), Re-N(l) 2.01(l), Re-N(2) 2.04(1) angstrom; O-Re-N(2) 162.7(6), O-Re-N(l) 109.0(7)-degrees. The interconversion between 'equatorial' and 'twisted' species is discussed. Elemental analyses, FAB mass, IR, electronic, H-1 and P-31 NMR spectra are reported. The P-31 NMR signal is diagnostic for both classes of complexes in solution, being a singlet for the 'equatorial' and two doublets for the 'twisted' species, respectively
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