522 research outputs found

    Structural characterization of 3d metal complexes containing an unconventional schiff base ligand

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    The design of appropriated organic ligands capable of binding metal ions provides a targeted entry to new materials with distinct structural and physicochemical properties. A representative family of such ligands includes Schiff bases. Here, we report new mono, diand polynuclear materials [Co(L)]3(ClO4)3·4H2O (1), [Zn2(L)(CH3COO)2] (2) and [Cu3(L)2(µ3 -ClO4)0.66](ClO4)1.33·1.33CHCl3 (3) containing N,N’-bis[(2- hydroxybenzilideneamino)-propyl]-piperazine (H2L) Schiff base as hexadentate ligand (Figure 1). The X-ray crystallography of the complexes reveal a retaining of the original chair piperazine conformation from the free ligand in the complex 2 and a changing into a boat conformation in the complexes 1 and 3. Moreover, in the respective complexes a different coordination number as 6 (1), 5 (2) and 4 and 5 (3) was observed upon coordination of the free ligand to Co(III), Zn(II) and Cu(II) ions. The modulatory property of H2L is reflected upon the molecular assembly and coordination mode of the isolable species

    Synthesis and structural characterization of dimeric and polymeric cooper(II) complexes with schiff base as ligand

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    Polynuclear coordination compounds derived from multidentate Schiff base ligands are a source of new materials with applications in catalysis [1], optoelectronic materials [2], and environmental applications [3]. In extension of our previous studies [4]on polynuclear materials, we report the crystal structures and spectroscopic properties ofdimeric and polymeric copper(II) complexeswith hexadentate Schiff base N,N’-bis[(2- hydroxybenzilideneamino)-propyl]-piperazine (H2L) as ligand. Reaction of Cu(ClO4)2 hexahydrate with H2L in the presence of triethylamine affords a polymeric structure [Cu3L2(μ3-ClO4)0.66](ClO4)1.33·1.33CHCl3(1) in which the perchlorate anion acts as a tridentate ligand in a μ3-manner binding three Cu3L2 units. When NaN3 was added to the above mentioned reaction mixturea new dimeric assembly[Cu6(C24H30N4O2)4(N3)2][ClO4]2 (2) was obtained in which two azide groups bridge two Cu3L2 unitsin an end-to-end fashion. The same dimeric structure was obtained when the polymer 1 was treated with NaN3

    A missing high-spin molecule in the family of cyano-bridged heptanuclear heterometal complexes, [(LCuII)6FeIII(CN)6]3+, and its CoIII and CrIII analogues, accompanied in the crystal by a novel octameric water cluster

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    Three isostructural cyano-bridged heptanuclear complexes, [{CuII(saldmen)(H2O)}6{MIII(CN)6}](ClO4)3\cdotp8H2O (M = FeIII 2; CoIII, 3; CrIII 4), have been obtained by reacting the binuclear copper(II) complex, [Cu2(saldmen)2(mu-H2O)(H2O)2](ClO4)2\cdotp2H2O 1, with K3[Co(CN)6], K4[Fe(CN)6], and, respectively, K3[Cr(CN)6] (Hsaldmen is the Schiff base resulted from the condensation of salicylaldehyde with N,N-dimethylethylenediamine). A unique octameric water cluster, with bicyclo[2,2,2]octane-like structure, is sandwiched between the heptanuclear cations in 2, 3 and 4. The cryomagnetic investigations of compounds 2 and 4 reveal ferromagnetic couplings of the central FeIII or CrIII ions with the CuII ions (JCuFe = +0.87 cm-1, JCuCr = +30.4 cm-1). The intramolecular Cu-Cu exchange interaction in 3, across the diamagnetic cobalt(III) ion, is -0.3 cm-1. The solid-state1H-NMR spectra of compounds 2 and 3 have been investigated

    Cyanomethylene-bis(phosphonate)-Based Lanthanide Complexes: Structural, Photophysical, and Magnetic Investigations

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    10 pagesInternational audienceThe syntheses, structural investigations, magnetic and photophysical properties of a series of 10 lanthanide mononuclear complexes, containing the heteroditopic ligand cyanomethylene-bis(5,5-dimethyl-2-oxo-1,3,2λ5-dioxa-phosphorinane) (L), are described. The crystallographic analyses indicate two structural types: in the first one, [LnIII(L)3(H2O)2]*H2O (Ln = La, Pr, Nd), the metal ions are eight-coordinated within a square antiprism geometry, while the second one, [LnIII(L)3(H2O)]*8H2O (Ln = Sm, Eu, Gd, Tb, Dy, Ho, Er), contains seven-coordinated LnIII ions within distorted monocapped trigonal prisms...

    Production of He-4 and (4) in Pb-Pb collisions at root(NN)-N-S=2.76 TeV at the LHC

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    Results on the production of He-4 and (4) nuclei in Pb-Pb collisions at root(NN)-N-S = 2.76 TeV in the rapidity range vertical bar y vertical bar <1, using the ALICE detector, are presented in this paper. The rapidity densities corresponding to 0-10% central events are found to be dN/dy4(He) = (0.8 +/- 0.4 (stat) +/- 0.3 (syst)) x 10(-6) and dN/dy4 = (1.1 +/- 0.4 (stat) +/- 0.2 (syst)) x 10(-6), respectively. This is in agreement with the statistical thermal model expectation assuming the same chemical freeze-out temperature (T-chem = 156 MeV) as for light hadrons. The measured ratio of (4)/He-4 is 1.4 +/- 0.8 (stat) +/- 0.5 (syst). (C) 2018 Published by Elsevier B.V.Peer reviewe

    Prevalence, associated factors and outcomes of pressure injuries in adult intensive care unit patients: the DecubICUs study

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    Funder: European Society of Intensive Care Medicine; doi: http://dx.doi.org/10.13039/501100013347Funder: Flemish Society for Critical Care NursesAbstract: Purpose: Intensive care unit (ICU) patients are particularly susceptible to developing pressure injuries. Epidemiologic data is however unavailable. We aimed to provide an international picture of the extent of pressure injuries and factors associated with ICU-acquired pressure injuries in adult ICU patients. Methods: International 1-day point-prevalence study; follow-up for outcome assessment until hospital discharge (maximum 12 weeks). Factors associated with ICU-acquired pressure injury and hospital mortality were assessed by generalised linear mixed-effects regression analysis. Results: Data from 13,254 patients in 1117 ICUs (90 countries) revealed 6747 pressure injuries; 3997 (59.2%) were ICU-acquired. Overall prevalence was 26.6% (95% confidence interval [CI] 25.9–27.3). ICU-acquired prevalence was 16.2% (95% CI 15.6–16.8). Sacrum (37%) and heels (19.5%) were most affected. Factors independently associated with ICU-acquired pressure injuries were older age, male sex, being underweight, emergency surgery, higher Simplified Acute Physiology Score II, Braden score 3 days, comorbidities (chronic obstructive pulmonary disease, immunodeficiency), organ support (renal replacement, mechanical ventilation on ICU admission), and being in a low or lower-middle income-economy. Gradually increasing associations with mortality were identified for increasing severity of pressure injury: stage I (odds ratio [OR] 1.5; 95% CI 1.2–1.8), stage II (OR 1.6; 95% CI 1.4–1.9), and stage III or worse (OR 2.8; 95% CI 2.3–3.3). Conclusion: Pressure injuries are common in adult ICU patients. ICU-acquired pressure injuries are associated with mainly intrinsic factors and mortality. Optimal care standards, increased awareness, appropriate resource allocation, and further research into optimal prevention are pivotal to tackle this important patient safety threat

    Structures étendues et discrètes dans la chimie de coordination en utilisant des ligands type base de Schiff tridentates et cyano bis-phosphonates

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    Thèse réalisée en co-tutelle Texte principal en roumain Résumé en françaisThis work develops new strategies in metallosupramolecular chemistry, based upon (1) new copper(II) precursors with easily accessible basal positions, that favor stronger exchange interactions, and flexible coordination spheres as a prerequisite for magnetic and photomagnetic processes; (2) cyano bis-phosphonate ligands for the construction of extended structure using building-block strategies; (3) tris-phosphonato triazine ligands together with coordination heteropolymetallic complexes with the paramagnetic centers Cu(II), Mn(II) and Co(II) as M(hfac)2 (hfac = hexafluoro-acetylacetonate) fragments. Here we report the results obtained by employing [Co(CN)6]3-[Cr(CN)6]3-,[Mo(CN)8]4-, [W(CN)8]4- as building-blocks and copper(II) precursors (synthesized by employing tridentate Schiff-base ligands allowing the access of the connectors to the basal position of the copper ions and thus providing to the copper ion a more flexible coordination sphere). Another series of homometallic systems was synthesized using the ligand 1-Cyanomethyl-bis(5,5-dimethyl-2-oxo-1,3,2-dioxaphosphorinane). The extended structures were built by the reaction of this units with a second metallic unit.La thèse présente de nouvelles stratégies dans la chimie métallo-supramoléculaire en utilisant, (1) des nouveaux précurseurs de cuivre (II) avec des positions basales accessibles, qui peuvent favoriser l'échange magnétique, et qui présentent aussi des sphères de coordinations flexibles pour l'obtention des matériaux magnétiques et photo magnétiques; (2) des ligands cyano-bisphosphonates pour l'obtention de réseaux étendus en utilisant la stratégie building-block; (3) des ligands tris-phosphonato-triazine pour l'obtention des complexes avec des centres paramagnétiques Cu(II), Mn(II) et Co(II) en utilisant des fragments M(hfac)2 (hfac = hexafluoro-acétylacétonate). Des nouveaux clusters hétérométalliques ont été obtenus en utilisant comme building-block [Co(CN)6]3-[Cr(CN)6]3-,[Mo(CN)8]4-, [W(CN)8]4- et précurseurs de cuivre (II), synthétisés à partir d'une base de Schiff tridentate qui peut permettre l'accès du connecteur dans le plan basal. Nous présenterons dans la thèse les résultats obtenus avec le ligand 1-Cyanométhylène-bis(5,5-diméthyl-2-oxo-1,3,2-dioxaphosphorinane ). Une série de complexes homométalliques a été synthétisée et caractérisée à l'état solide par diffraction des rayons X sur monocristal. La réaction de ces unités de construction avec un deuxième centre métallique conduit à des systèmes supramoléculaires étendus
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