1,361,242 research outputs found
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
A simple combinatorial proof of a generalization of a result of Polo Author: F. Caselli Representation Theory 8 (2004), 479-486
No full textWe provide a simple combinatorial proof of, and generalize, a theorem
of Polo which asserts that for any polynomial P with nonnegative integer
coefficients such that P(0)=1 there exist two permutations u and v in a
suitable symmetric group such that P is equal to the Kazhdan-Lusztig
polynomial Pu,v
Le best practice internazionali: il caso delle SBIC - Small Bsuiness Investment Company americane
No full textIl lavoro sviluppa un'analisi delle caratteristiche del mercato delle SBIC americane, valutandone l'impatto sotto il profilo della performance degli investimenti effettuati. L'analisi descrive per la prima volta il frenomeno, tracciandone l'evoluzione a partire dal 1958, anno in cui sono state introdotte nell'ordinamento americano per sostenere la crescita del private equity
Gelfand models and Robinson–Schensted correspondence
No full textIn F. Caselli (Involutory reflection groups and their models, J. Algebra
24:370–393, 2010), a uniform Gelfand model is constructed for all nonexceptional
irreducible complex reflection groups which are involutory. Such models can be
naturally decomposed into the direct sum of submodules indexed by Sn-conjugacy
classes, and we present here a general result that relates the irreducible decomposition of these submodules with the projective Robinson–Schensted correspondence.
This description also reflects, in a very explicit way, the existence of split representations for these groups
Refined Gelfand models for wreath products
No full textAbstractIn [F. Caselli, Involutory reflection groups and their models, J. Algebra 24 (2010), 370–393] there is constructed a uniform Gelfand model for all non-exceptional irreducible complex reflection groups which are involutory. This model can be naturally decomposed into the direct sum of submodules indexed by symmetric conjugacy classes, and in this paper we present a simple combinatorial description of the irreducible decomposition of these submodules if the group is the wreath product of a cyclic group with a symmetric group. This is attained by showing that such decomposition is compatible with the generalized Robinson–Schensted correspondence for these groups
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
Chiovenda Piola Caselli Lucia
No full textChiovenda Piola Caselli Lucia; profilo e impegno educativo nell'ambito dell'Associazione Guide Italiane
How structural modifications can tune the asymmetric cyclopropanations catalyzed by Cu(I) complexes of chiral pyridine containing macrocylcic ligands (Pc-L*)
No full textWe have recently reported that copper(I) complexes of the new C1-symmetric pyridine-based 12-membered tetraaza macrocycles, Pyridine Containing Ligands (Pc-L*), are competent catalysts in the asymmetric cyclopropanation.[1] We report here the synthesis of new C1- and C2-symmetric Pc-L* macrocycles and the use of their Cu(I) complexes as catalysts for the title reaction. The synthetic paths, reportedi in Scheme 1, are very simple and they take advantage of commercially available, enantiomerically pure, chiral amino-alcohols and/or primary amines. These last compounds can react either with 2,6-bis(chloromethyl)pyridine(path A) or with the stereochemically pure forms of the alkyl pyridines obtained by the Lipase-catalyzed kinetic acetylation of 2,6-bis(1-hydroxyethyl)pyridine [2] (path B).
Ligands with different structures have been obtained in moderate to good yields (40-80%) and they have been fully characterized. The Cu(I) complexes of those ligands showed good catalytic activities in the cyclopropanation of differently substituted olefins employing ethyl diazoacetate (EDA) as carbene precursor.
In all cases a complete conversion of EDA was observed and, depending on the employed ligand, cyclopropanes were obtained with tunable cis/trans stereoselectivities and e.e. up to 96%.
[1] Caselli, A.; Cesana, F.; Gallo, E.; Casati, N.; Macchi, P.; Sisti, M.; Celentano, G.; Cenini, S. Dalton Trans. 2008, 4202-4205. [2] Uenishi, J.; Aburatani, S.; Takami, V. J. Org. Chem., 2007, 72, 132-138
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