2,280 research outputs found
Special matchings and permutations in Bruhat orders
No full textFor any permutation v, we show that the special matchings of v generate a Coxeter system. This gives new necessary conditions on an abstract poset to be isomorphic to a lower Bruhat interval of the symmetric group, and also answers in the affirmative, in the symmetric group case, a problem posed in [F. Brenti, F. Caselli, M. Marietti, Special matchings and Kazhdan-Lusztig polynomials, Adv. Math. 202 (2006) 555601]. (c) 2006 Elsevier Inc. All rights reserved
Catalytic Applications of Pyridine-Containing Macrocyclic Complexes
No full textPolyazamacrocycles are a common class of macrocyclic compounds, utilized across a number of fields, including, but not limited to, catalysis, selective metal recovery and recycling, therapy and diagnosis, and materials and sensors.1 Worth of note is their ability to form stable complexes with a plethora of both transition, especially late, and lanthanide metal cations.2 Deviation of the macrocycle donor atoms from planarity often leads to rather uncommon oxidation states.3 Both the thermodynamic properties and the complexation kinetics are strongly affected by the introduction of a pyridine moiety into the skeleton of polyazamacrocycles by increasing the conformational rigidity and tuning the basicity.4 Pyridine-containing ligands engender great interest due to various potential field of applications. They have been successfully employed in biology, Magnetic Resonance Imaging, molecular recognition, supramolecular chemistry and self-assembly, molecular machines and mechanically interlocked architectures.5 In this lecture, I will provide a perspective on the catalytic applications of metal complexes of pyridine-containing macrocyclic ligands (Pc-L’s) which have been studied in our group (Figure), with a focus interest on the structural features relevant to catalysis.6 The increased conformational rigidity imposed by the pyridine ring allowed for the isolation and characterization of metal complexes which showed a rich coordination chemistry.7 The very different conformations accessible upon coordination and the easy tuneable synthesis of the macrocyclic ligands have been exploited in stereoselective syntheses.8
References:
1 L. F. Lindoy, G. V. Meehan, I. M. Vasilescu, H. J. Kim, J.-E. Lee, S. S. Lee, Coord. Chem. Rev. 2010, 254, 1713.
2 T. Ren, Chem. Commun. 2016, 52, 3271.
3 A. Casitas, X. Ribas, Chem. Sci. 2013, 4, 2301.
4 K. M. Lincoln, M. E. Offutt, T. D. Hayden, R. E. Saunders, K. N. Green, Inorg. Chem. 2014, 53, 1406.
5 M. Rezaeivala, H. Keypour, Coord. Chem. Rev. 2014, 280, 203.
6 B. Castano, S. Guidone, E. Gallo, F. Ragaini, N. Casati, P. Macchi, M. Sisti, A. Caselli, Dalton Trans. 2013, 42, 2451.
7 a) G. Tseberlidis, M. Dell'Acqua, D. Valcarenghi, E. Gallo, E. Rossi, G. Abbiati, A. Caselli, RSC Adv. 2016, 6, 97404; b) T. Pedrazzini, P. Pirovano, M. Dell'Acqua, F. Ragaini, P. Illiano, P. Macchi, G. Abbiati, A. Caselli, Eur. J. Inorg. Chem. 2015, 2015, 5089.
8 a) M. Dell’Acqua, B. Castano, C. Cecchini, T. Pedrazzini, V. Pirovano, E. Rossi, A. Caselli, G. Abbiati, J. Org. Chem. 2014, 79, 3494; b) M. Trose, M. Dell’Acqua, T. Pedrazzini, V. Pirovano, E. Gallo, E. Rossi, A. Caselli, G. Abbiati, J. Org. Chem. 2014, 79, 7311; c) B. Castano, E. Gallo, D. J. Cole-Hamilton, V. Dal Santo, R. Psaro, A. Caselli, Green Chem. 2014, 16, 3202
Designing new Ligands: Catalytic Applications of Pyridine-Containing Macrocyclic Complexes
No full textThe introduction of a pyridine moiety into the skeleton of a polyazamacrocyclic ligand affects both the thermodynamic properties and the coordination kinetics of the resulting metal complexes. These features have engender a great interest in the scientific community and the applications of pyridine-containing macrocyclic ligands ranges from biology to supramolecular chemistry, encompassing MRI, molecular recognitions, materials and catalysis. In this lecture, I will provide a perspective on the catalytic applications of metal complexes of pyridine-containing macrocyclic ligands (Pc-L’s) which have been studied in our group (Figure 1), with a focus interest on the structural features relevant to catalysis.1 The increased conformational rigidity imposed by the pyridine ring allowed for the isolation and characterization of metal complexes which show a rich coordination chemistry.2 The very different conformations accessible upon coordination and the easy tuneable synthesis of the macrocyclic ligands have been exploited in stereoselective syntheses.3
References
1 B. Castano, S. Guidone, E. Gallo, F. Ragaini, N. Casati, P. Macchi, M. Sisti, A. Caselli, Dalton Trans. 2013, 42, 2451.
2 a) G. Tseberlidis, M. Dell'Acqua, D. Valcarenghi, E. Gallo, E. Rossi, G. Abbiati, A. Caselli, RSC Adv. 2016, 6, 97404; b) T. Pedrazzini, P. Pirovano, M. Dell'Acqua, F. Ragaini, P. Illiano, P. Macchi, G. Abbiati, A. Caselli, Eur. J. Inorg. Chem. 2015, 2015, 5089.
3 a) M. Dell’Acqua, B. Castano, C. Cecchini, T. Pedrazzini, V. Pirovano, E. Rossi, A. Caselli, G. Abbiati, J. Org. Chem. 2014, 79, 3494; b) M. Trose, M. Dell’Acqua, T. Pedrazzini, V. Pirovano, E. Gallo, E. Rossi, A. Caselli, G. Abbiati, J. Org. Chem. 2014, 79, 7311; c) B. Castano, E. Gallo, D. J. Cole-Hamilton, V. Dal Santo, R. Psaro, A. Caselli, Green Chem. 2014, 16, 3202
Selective oxidation of alkenes by H2O2 catalysed by well-defined [Iron(III)(Pyridine-Containing Ligand)] complexes
No full textThe introduction of a pyridine moiety into the skeleton of a polyazamacrocyclic ligand affects both thermodynamic properties and coordination kinetics of the resulting metal complexes (1). These features have engendered a great interest of the scientific community in recent years. The applications of pyridine-containing macrocyclic ligands ranges from biology to supramolecular chemistry, encompassing MRI, molecular recognitions, materials and catalysis. Much of the efforts in the use of macrocyclic pyridine containing ligands have been devoted to the study of catalytic oxidation reactions. We report here the synthesis and characterization of [Fe(III)Pc-L’s)] complexes (Pc-L = Pyiridine-Containing Ligand) and their catalytic applications in alkene epoxidation or cis-dihydroxylation reactions using H2O2 as the terminal oxidant under mild conditions (Figure). Depending on the anion employed for the synthesis of the iron(III) metal complex, we observed a completely reversed selectivity. When X = OTf, a selective cis-dihydroxylation reaction was observed. On the other hand, employing X = Cl, we obtained the epoxide as the major product (traces of aldehyde were observed at very high conversions). It should be pointed out that under otherwise identical reaction conditions, using FeCl3·6H2O as catalyst in the absence of the ligand, no reaction was observed.
References:
1 a) B. Castano, S. Guidone, E. Gallo, F. Ragaini, N. Casati, P. Macchi, M. Sisti, A. Caselli, Dalton Trans. 2013, 42, 2451; b) G. Tseberlidis, M. Dell'Acqua, D. Valcarenghi, E. Gallo, E. Rossi, G. Abbiati, A. Caselli, RSC Adv. 2016, 6, 97404; c) T. Pedrazzini, P. Pirovano, M. Dell'Acqua, F. Ragaini, P. Illiano, P. Macchi, G. Abbiati, A. Caselli, Eur. J. Inorg. Chem. 2015, 2015, 5089
Lipschitz continuity results for a class of obstacle problems
No full textWe prove Lipschitz continuity results for solutions to a class of obstacle problems under standard growth conditions of p-type, p b 2. The main novelty is the use of a linearization technique going back to [28] in order to interpret our constrained minimizer as a solution to a nonlinear elliptic equation, with a bounded right hand side. This lead us to start a Moser iteration scheme which provides the Ll bound for the gradient. The application of a recent higher di¤erentiability result [24] allows us to simplify the procedure of the identification of the Radon measure in the linearization technique employed in [32]. To our knowdledge, this is the first result for nonautomonous functionals with standard growth conditions in the direction of the Lipschitz regularity
Interazioni comunicative nello sviluppo tipico e atipico: implicazioni per la ricerca e il trattamento
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Competenze linguistiche e modalità interattive: bambini con profili tipici, atipici e a rischio a confronto. Introduzione al simposio.
No full textPer comprendere i processi coinvolti nell’acquisizione e nell’uso di abilità comunicative e linguistiche è estremamente utile confrontare diverse popolazioni di bambini, con sviluppo tipico e con profili cognitivi e/o linguistici atipici o a rischio. E’ inoltre importante esaminare specifiche competenze e le loro relazioni, in più momenti evolutivi, tenendo conto della continua interazione tra maturazione neurobiologica e stimolazioni ambientali (Karmiloff-Smith, 2007). Questo simposio si propone quindi di presentare alcune ricerche che hanno indagato diversi aspetti, individuali e interattivi, dello sviluppo linguistico nell’infanzia e in età prescolare, con rigorosi criteri metodologici. A tal fine gruppi di bambini con disturbi/difficoltà di linguaggio, determinati da sindromi genetiche (sindrome di Down –SD), disturbi evolutivi specifici (ritardo/disturbo specifico del linguaggio – R/DSL) e condizioni neonatali di rischio (nascita pretermine – NP) sono stati messi a confronto con bambini con sviluppo tipico (ST).
In particolare, tre ricerche hanno esaminato specifiche competenze linguistiche e le loro relazioni in bambini con sviluppo atipico (lessico e morfosintassi in bambini con SD; lessico e semantica in bambini con DSL) e a rischio (lessico, grammatica e consapevolezza fonologica in bambini con NP), individuando alcune peculiari difficoltà/disturbi, ma al tempo stesso relazioni tra le competenze. Altre due ricerche hanno invece analizzato le strategie comunicative tra madre e bambino con sviluppo atipico (bambini con SD e bambini con R/DSL), evidenziando differenze nelle modalità comunicative rispetto alle coppie madre-bambino con ST, ma al tempo stesso una reciproca influenza tra enunciati materni e responsività infantile in tutti i gruppi
Delineation of target volume for radioteraphy in SPECT images: stamement and analysis of two novel algorithms
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