30,716 research outputs found
Italiano come L2
No full textSintesi dei principali esiti della recente ricerca acquisizionale sull'italiano L2, con particolare attenzione (nei parr. scritti da M. Chini) a fonetica e fonologia, lessico, testualità e variazione. In altri parr. sono trattati altri livelli dell'italiano L2 (morfologia, sintassi), aspetti metodologici, corpora di L2, ricadute didattiche
Functionalization, Modification, and Transformation of Platinum Chini Clusters
No full textIn this microreview, the authors summarize the reactions of [Pt3n(CO)6n]2-(n = 1-10) Chini clusters aimed at their functionalization, modification and transformation. The results are organized on the basis of the fact that the final products do or do not retain the structure of the parent Chini clusters. The first category comprises the redox reactions of homoleptic Chini clusters, CO/phosphine substitution affording heteroleptic Chini-type clusters and the formation of Lewis acid-base adducts by capping the external Pt3-triangular faces with Lewis acids. The second category consists of globular molecular platinum nanoclusters (platinum browns) obtained by thermal decomposition of Chini clusters, as well as surface decorated platinum carbonyl clusters, composed of a low valent Pt-CO core decorated by cationic metal fragments. The relevance of such species to molecular cluster chemistry and metal nanoclusters is outlined
Maria Bersani
No full textLa voce illustra la biografia e l'apporto letterario dato da Maria Bersani alla letteratura per l'infanziaThe headword explains the biography and the contribution of the author Maria Bersani to the children's literatur
Further insights into platinum carbonyl Chini clusters
No full textThe oxidation of [Ph3P(CH2)12PPh3][Pt15(CO)30] with CF3COOH in THF afforded [Ph3P(CH2)12PPh3][Pt18(CO)36] as a precipitate which was re-crystallized from dmf/iso-propanol. This salt self-assembles in the solid state adopting an unprecedented morphology which consists of infinite chains of [Pt9(CO)18]– units. The solid state structure of [Ph3P(CH2)12PPh3][Pt18(CO)36] may be viewed as a snapshot in which [Pt9(CO)18]– units are approaching and ready to exchange outer Pt3(CO)6 fragments. The reactions of Chini clusters with isonitriles proceed via redox-fragmentation, at difference with those involving phosphines that may occur both via non-redox substitution and redox fragmentation, depending on the experimental conditions. Thus, the reaction of [Pt6(CO)12]2– with CNXyl afforded Pt5(CNXyl)10, whereas Pt9(CNXyl)13(CO) was obtained from the reaction of [Pt15(CO)30]2– with CNXyl. These two new neutral clusters have been structurally characterized as their Pt5(CNXyl)10·2toluene and Pt9(CNXyl)13(CO)·solv solvates. DFT studies on the CO exchange of [Pt6(CO)12]2– suggest an associative interchange mechanism, which may be extended also to larger Chini clusters and the initial steps of their reactions with other soft nucleophiles
Computational NMR Methods in the Stereochemical Analysis of Organic Compounds: Are Proton or Carbon NMR Chemical Shift Data More Discriminating?
No full textWe have investigated the H-1 and C-13 NMR chemical shift data of a large set of stereoisomeric organic compounds to determine whether it is possible to identify the nucleus that is more discriminating in stereochemical analyses conducted by quantum mechanical methods. By estimating the intrinsic deviation of the experimental chemical shifts of 219 pairs of diastereoisomers, we have reconsidered the concept of the match ratio as an inequality, namely H-1 match ratio > C-13 match ratio, mathematically demonstrating that the H-1 nucleus is more discriminating than the C-13 nucleus for all the investigated cases. Moreover, we have also verified that this inequality is satisfied by the most often used quantum chemical methods, which suggests that H-1 chemical shifts are more discriminating than C-13 chemical shifts in stereochemical assignments by quantum chemical calculations
Variations on the Author
No full text“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
Fibril aggregation inhibitory activity of the β-sheet breaker peptides: a molecular docking approach
No full textO curso de licenciatura em educação física da Universidade Federal de Santa Catarina: suas concepções de ensino e de educação física
No full textDissertação (mestrado) - Universidade Federal de Santa Maria. Centro de Educação Fisica e Desporto
Heteroleptic Chini-Type Platinum Clusters: Synthesis and Characterization of Bis-Phospine Derivatives of [Pt3n(CO)6n]2- (n = 2-4)
No full textThe reactions of [Pt3n(CO)6n]2- (n = 2-4) homoleptic Chini-type clusters with stoichiometric amounts of Ph2PCH2CH2PPh2 (dppe) result in the heteroleptic Chini-type clusters [Pt6(CO)10(dppe)]2-, [Pt9(CO)16(dppe)]2-, and [Pt12(CO)20(dppe)2]2-. Their formation is accompanied by slight amounts of neutral species such as Pt4(CO)4(dppe)2, Pt6(CO)6(dppe)3, and Pt(dppe)2. A similar behavior was observed with the chiral ligand R-Ph2PCH(Me)CH2PPh2 (R-dppp), and two isomers of [Pt9(CO)16(R-dppp)]2- were identified. All the new species were spectroscopically characterized by means of IR and 31P NMR, and their structures were determined by single-crystal X-ray diffraction. The results obtained are compared to those previously reported for monodentate phosphines, that is, PPh3, as well as more rigid bidentate ligands, that is, CH2C(PPh2)2 (P^P), CH2(PPh2)2 (dppm), and o-C6H4(PPh2)2 (dppb). From a structural point of view, functionalization of anionic platinum Chini clusters preserves their triangular Pt3 units, whereas the overall trigonal prismatic structures present in the homoleptic clusters are readily deformed and transformed upon functionalization. Such transformations may be just local deformations, as found in [Pt9(CO)16(dppe)]2-, [Pt9(CO)16(R-dppp)]2-, [Pt12(CO)22(PPh3)2]2-, and [Pt9(CO)16(PPh3)2]2-; an inversion of the cage from trigonal prismatic to octahedral, as observed in [Pt6(CO)10(dppe)]2- and [Pt6(CO)10(PPh3)2]2-; the reciprocal rotation of two trigonal prismatic units with the loss of a Pt-Pt contact as found in [Pt12(CO)20(dppe)2]2-
Quantum Mechanical Calculation of NMR Parameters in the Stereostructural Determination of Natural Products
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