10 research outputs found
Self-assembly of a cavitand-based heteronuclear coordination cage
No full textA new self-assembly protocol leading to the formation of heteronuclear coordination cage 10 is reported. Reaction of tetradentate cavitand ligand 1, bearing one ethynylpyridine and three benzonitriles at the apical positions, with Pt(dppp)OTf2 and Pd(dppp)OTf2 in a 1:3 ratio yields 10 as the thermodynamic product. Under the same conditions, the self-assembly of 1 with either Pt or Pd metal precursors gives a mixture of isomeric homonuclear cages 8a-c or 9a-c, respectively
Cavitand-Based Coordination Cages: Achievements and Current Challenges
No full textThe research results obtained in the self-assembly of cavitand-based coordination cages are presented. Cavitands are ideal multidentate ligands for the creation of coordination cages due to their structural rigidity, concave structure, and great versatility in terms of synthetic modularity. The introduction of the ligand moieties on the resorcinarene building block proceeds at the upper rim of the cavity, to take full advantage of the structural rigidity of the cavitand scaffold. Two different synthetic strategies are employed for the formation of multidentate cavitand ligands: (a) functionalization at the apical positions and (b) introduction of the ligands as bridging units. The key features to control the cage self-assembly process emerging from this overview are the preorganization, for the cavitands, and kinetic versus thermodynamic stability of the resulting complexes, for the connecting metal. The versatility of this class of coordination cages is demonstrated by the formation of their heterotopic and heteronuclear versions, as well as their self-assembly on gold and silicon surfaces. Desymmetrization of the cages is appealing because of the resulting differentiation of the inner cavities in terms of shape and interactivity, while surface self-assembly represents an important opportunity to expand the application range of these objects
Molecular Recognition with Ditopic Cavitand Re-Complexes
No full textThe synthesis of a series of cavitand receptors bearing increasing numbers of phosphonate groups at their upper rims and of the corresponding Re-based ditopic complexes is reported. The molecular recognition properties of these phosphonate cavitands towards both monotopic and ditopic N-methylpyridinium salts were investigated. The numbers and spatial dispositions of P=O units are pivotal for the complexation of guest ions. The removal of a single P=O bridge from the parent tetraphosphonate cavitand was sufficient to reduce the association constant by almost three orders of magnitude. Elimination of a second P=O unit completely abolished complexation in the AC distal isomer, both in monotopic and in ditopic hosts. The preorganised structure obtained by interconnection of two triphosphonate cavitands through a Re system showed moderate positive self-assembly cooperativity in the inclusion of ditopic N-methylpyridinium salts in both polar and nonpolar solvents. The speciation profile in ethanol indicates that the clamshell 1: 1 complex is dominant at low concentrations (< 10(-4) M) whereas the 1: 2 complex is preferred at higher concentrations of ditopic guest
Synthesis of Partially-Bridged Phosphonate and Thiophosphonate Resorcinarenes
No full textThe synthesis of partially bridged thiophosphonate and phosphonate resorcinarenes is reported in this paper. Resorcinarenes functionalised at the upper rim with two or three P=X (X=S,O) bridges oriented towards the molecular cavity are obtained from the treatment of the corresponding (iiii) tetrasubstituted cavitand with 1,2-dihydroxybenzene and base in DMF. This synthetic route selectively promoted the formation of one of the two disubstituted resorcinarenes, the AC isomer. The crystal structure of the AC-dithiophosphonated resorcinarene 4 has been determined
Author Correction: Using mortuary and burial data to place COVID-19 in Lusaka, Zambia within a global context
No full textCorrection to: Nature Communicationshttps://doi.org/10.1038/s41467-023-39288-6, published online 29 June 2023 In this Article, the affiliation details for Emanuele Del Fava & Alessia Melegaro were incorrectly given as ‘Carlo F. Dondena Centre for Research on Social Dynamics and Public Policy, Boccini University, Milan, Italy’ but should have been ‘Carlo F. Dondena Centre for Research on Social Dynamics and Public Policy, Bocconi University, Milan, Italy’. This has now been corrected in the PDF and HTML versions of the Article
Mechanistic Studies of the Oxidation of Oxyhemoglobin by Peroxynitrite<sup>†</sup>
No full textThe strong oxidizing and nitrating agent peroxynitrite has been shown to diffuse into erythrocytes
and oxidize oxyhemoglobin (oxyHb) to metHb. Because the value of the second-order rate constant for
this reaction is on the order of 104 M-1 s-1 and the oxyHb concentration is about 20 mM (expressed per
heme), this process is rather fast and oxyHb is considered a sink for peroxynitrite. In this work, we
showed that the reaction of oxyHb with peroxynitrite, both in the presence and absence of CO2, proceeds
via the formation of oxoiron(iv)hemoglobin (ferrylHb), which in a second step is reduced to metHb and
nitrate by its reaction with NO2•. In the presence of physiological relevant amounts of CO2, ferrylHb is
generated by the reaction of NO2• with the coordinated superoxide of oxyHb (HbFeIIIO2•-). This reaction
proceeds via formation of a peroxynitrato−metHb complex (HbFeIIIOONO2), which decomposes to generate
the one-electron oxidized form of ferrylHb, the oxoiron(iv) form of hemoglobin with a radical localized
on the globin. CO3•-, the second radical formed from the reaction of peroxynitrite with CO2, is also
scavenged efficiently by oxyHb, in a reaction that finally leads to metHb production. Taken together, our
results indicate that oxyHb not only scavenges peroxynitrite but also the radicals produced by its
decomposition
Education in Europe: anything but uniform. Europe: Magazine of the European Community No. 329, September 1993
No full textTres fragmentos en escritura visigótica conservados en la Biblioteca KBR de Bruselas
No full textLa Biblioteca KBR de Bruselas guarda tres fragmentos manuscritos en escritura visigótica carentes de estudio hasta el momento. En este artículo se analizarán desde una perspectiva codicológica y filológica a fin de esclarecer su origen y determinar sus contenidos. La conclusión es que se trata de tres fragmentos procedentes de sendos códices conservados en la Biblioteca Capitular de Toledo. Uno de ellos contiene un fragmento de las Homiliae in Ezechielem de Gregorio Magno (Toledo, BC, 9-6); y los otros dos son fragmentos litúrgicos procedentes de un Liber horarum Toletanus (Toledo, BC, 33-3) y un Liber missarum Toletanus (Toledo, BC, 35-3).MCIN/AEI/10.13039/50110001103
