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1.
Chemistry ; 25(40): 9390-9394, 2019 Jul 17.
Artigo em Inglês | MEDLINE | ID: mdl-30714647

RESUMO

Despite the known nucleophilic nature of [M(CF3 )2 ]- (M=Cu, Ag, Au) complexes, their participation in trifluoromethylation reactions of aryl halides remains unexplored. Here, for the first time, selective access to a [Cu(CF3 )2 ]- species is reported, which is ubiquitous in Cu-mediated trifluoromethylations, and we rationalize its complex mechanistic scenario as well as its behavior compared to its silver and gold congeners through a combination of experimental and computational approaches.

2.
Chemistry ; 24(65): 17225-17229, 2018 Nov 22.
Artigo em Inglês | MEDLINE | ID: mdl-30189118

RESUMO

An innovative approach to position-selective polyhalogenation of aliphatic hydrocarbon bonds is presented. The reaction proceeded within the Hofmann-Löffler manifold with amidyl radicals as the sole mediators to induce selective 1,5- and 1,6-hydrogen-atom transfer followed by halogenation. Multiple halogenation events of up to four innate C-H bond functionalizations were accomplished. The broad applicability of this new entry into polyhalogenation and the resulting synthetic possibilities were demonstrated for a total of 27 different examples including mixed halogenations.

3.
Angew Chem Int Ed Engl ; 57(35): 11203-11207, 2018 Aug 27.
Artigo em Inglês | MEDLINE | ID: mdl-29742311

RESUMO

An unprecedented organocatalytic approach towards highly substituted cyclic carbonates from tri- and tetrasubstituted oxiranes and carbon dioxide has been developed. The protocol involves the use of a simple and cheap superbase under mild, additive- and metal-free conditions towards the initial formation of a less substituted carbonate product that equilibrates to a tri- or even tetrasubstituted cyclic carbonate under thermodynamic control. The latter are conveniently trapped in situ, providing overall a new domino process for synthetically elusive heterocyclic scaffolds. Control experiments provide a rationale for the observed cascade reactions, which demonstrate similarity to the well-known Payne rearrangement of epoxy alcohols.

4.
Angew Chem Int Ed Engl ; 55(7): 2435-40, 2016 Feb 12.
Artigo em Inglês | MEDLINE | ID: mdl-26749029

RESUMO

Current methods for creatinine quantification suffer from significant drawbacks when aiming to combine accuracy, simplicity, and affordability. Here, an unprecedented synthetic receptor, an aryl-substituted calix[4]pyrrole with a monophosphonate bridge, is reported that displays remarkable affinity for creatinine and the creatininium cation. The receptor works by including the guest in its deep and polar aromatic cavity and establishing directional interactions in three dimensions. When incorporated into a suitable polymeric membrane, this molecule acts as an ionophore. A highly sensitive and selective potentiometric sensor suitable for the determination of creatinine levels in biological fluids, such as urine or plasma, in an accurate, fast, simple, and cost-effective way has thus been developed.


Assuntos
Creatinina/análise , Creatinina/sangue , Creatinina/urina , Humanos , Espectroscopia de Prótons por Ressonância Magnética
5.
Inorg Chem ; 54(10): 4678-87, 2015 May 18.
Artigo em Inglês | MEDLINE | ID: mdl-25950646

RESUMO

The reaction of 1,2,4-triazole and NaF with M(ox) (M = transition-metal dication; ox = oxalate dianion) under hydrothermal conditions has led to the isolation of a variety of hybrid organic-inorganic coordination polymers. Four structurally different 3D networks were obtained, depending on the transition metal, with stoichiometry [M2(H2O)(µ2-ox)][M2(µ3-trz)6] [M = Fe (1), Co (2), Ni (3)], [Zn2(H2O)(µ3-trz)2(µ2-ox)] (4), [Mn3(µ3-trz)2(µ6-ox)(µ3-F)2] (5), and [Fe3(µ3-trz)2(µ6-ox)(µ2-F)2] (6). In all cases, the magnetic behavior is dominated by antiferromagnetic exchange interactions between paramagnetic centers. Remarkably, 5 and 6 present a novel magnetic connectivity around the oxalate anion: a µ6-bridging mode. This magnetic geometry promotes multiple triangular arrangements among antiferromagnetically coupled spin carriers, resulting in a complex magnetic network because of the presence of competing interactions. These materials exhibit spontaneous magnetization below 9 and 66 K, respectively.

6.
Angew Chem Int Ed Engl ; 54(17): 5218-22, 2015 Apr 20.
Artigo em Inglês | MEDLINE | ID: mdl-25726937

RESUMO

Four new well-defined Cu(I) complexes bearing a C2 F5 ligand have been prepared and fully characterized: [(Ph3 P)2 CuC2 F5 ] (2), [(bpy)CuC2 F5 ] (3), [(Ph3 P)Cu(phen)C2 F5 ] (4), and [(IPr*)CuC2 F5 ] (5). X-ray structures of all four have been determined, showing that the C2 F5 -ligated Cu atom can be di- (5), tri- (2 and 3), and tetracoordinate (4). The mixed phen-PPh3 complex 4 is a highly efficient fluoroalkylating agent for a broad variety of acid chlorides. This high-yielding transformation represents the first general method for the synthesis of RCOC2 F5 from the corresponding RCOCl.


Assuntos
Cloretos/química , Complexos de Coordenação/química , Cobre/química , Flúor/química , Cristalografia por Raios X , Cetonas/síntese química , Cetonas/química , Conformação Molecular , Fenantrolinas/química
7.
Chemistry ; 20(40): 12817-25, 2014 Sep 26.
Artigo em Inglês | MEDLINE | ID: mdl-25137217

RESUMO

Double-decker complexes of lanthanide cations can be readily prepared with tetraazaporphyrins (porphyrazines). We have synthesized and characterized a series of neutral double-decker complexes [Ln(OETAP)2 ] (Ln=Tb(3+), Dy(3+), Gd(3+), Y(3+); OETAP=octa(ethyl)tetraazaporphyrin). Some of these complexes show analogous magnetic features to their phthalocyanine (Pc) counterparts. The Tb(3+) and Dy(3+) derivatives exhibit single-molecule magnet (SMM) behavior with high blocking temperatures over 50 and 10 K, respectively. These results confirm that, in double-decker complexes that involve Tb or Dy, the (N4)2 square antiprism coordination mode has an important role in inducing very large activation energies for magnetization reversal. In contrast with their Pc counterparts, the use of tetraazaporphyrin ligands endows the presented [Ln(OETAP)2] complexes with extraordinary chemical versatility. The double-decker complexes that exhibit SMM behavior are highly soluble in common organic solvents, and easily processable even through sublimation.

8.
J Am Chem Soc ; 135(22): 8324-30, 2013 Jun 05.
Artigo em Inglês | MEDLINE | ID: mdl-23672588

RESUMO

Herein we disclose the results of our investigations regarding the interactions between the biologically relevant nitrate oxoanion and several "two-wall" aryl-extended calix[4]pyrroles. There exists a clear relationship between the electronic nature of the aromatic walls of the calix[4]pyrroles and the stability of the nitrate⊂calix[4]pyrrole complex. This suggests that NO3(-)-π interactions have an important electrostatic component. We provide energetic estimates for the interaction of nitrate with several phenyl derivatives. Additionally, we report solid-state evidence for a preferred binding geometry of the nitrate anion included in the calix[4]pyrroles. Finally, the "two-wall" aryl-extended calix[4]pyrroles show excellent activity in ion transport through lipid-based lamellar membranes. Notably the best anion transporters are highly selective for transport of nitrate over other anions.


Assuntos
Calixarenos/química , Hidrocarbonetos Aromáticos/química , Nitratos/química , Porfirinas/química , Modelos Moleculares , Estrutura Molecular , Termodinâmica
9.
Chemistry ; 19(8): 2641-8, 2013 Feb 18.
Artigo em Inglês | MEDLINE | ID: mdl-23355284

RESUMO

A tetraoxo bis-Zn(salphen) supramolecular host can bind various divalent metal salts, thereby providing access to trinuclear bifunctional systems that incorporate both Lewis acid sites and dynamically bound nucleophilic anions. The formation of these trinuclear species was investigated and their stability features were also determined. The application of these trinuclear complexes as bifunctional catalysts was evaluated in the formation of cyclic organic carbonates from epoxides and CO(2). The catalytic data, in combination with control experiments, clearly demonstrate that these trinuclear compounds show much higher recycling potential compared to various control compounds and they can be used in up to five cycles without an observable loss in activity. Furthermore, this new recyclable catalytic system does not require any additives and can be applied under solvent-free conditions.

10.
Front Chem ; 11: 1163178, 2023.
Artigo em Inglês | MEDLINE | ID: mdl-37153526

RESUMO

A self-assembled tetrahedral cage results from two C 3-symmetry building blocks, namely, homooxacalix[3]arene tricarboxylate and uranyl cation, as demonstrated by X-ray crystallography. In the cage, four metals coordinate at the lower rim with the phenolic and ether oxygen atoms to shape the macrocycle with appropriate dihedral angles for tetrahedron formation, whereas four additional uranyl cations further coordinate at the upper-rim carboxylates to finalize the assembly. Counterions dictate the filling and porosity of the aggregates, whereas potassium induces highly porous structures, and tetrabutylammonium yields compact, densely packed frameworks. The tetrahedron metallo-cage complements our previous report (Pasquale et al., Nat. Commun., 2012, 3, 785) on uranyl-organic frameworks (UOFs) from calix[4]arene and calix[5]arene carboxylates (octahedral/cubic and icosahedral/dodecahedral giant cages, respectively) and completes the assembly of all five Platonic solids from just two chemical components.

11.
Chemistry ; 18(22): 6805-10, 2012 May 29.
Artigo em Inglês | MEDLINE | ID: mdl-22522915

RESUMO

Supramolecular chirality effects have been achieved both for ditopic and monotopic substrates by using a programmable bis-salphen scaffold that incorporates either two or three Zn nuclei. The dinuclear host shows preferential chirogenesis in the presence of ditopic systems, whereas effective chirality transfer to the trinuclear complex is realized through monotopic binding. The mode of binding in the trinuclear host has been investigated through X-ray crystallography, CD measurements, UV/Vis spectroscopy, and DFT analysis. The bis-salphen scaffold holds promise for the development of substrate-specific host systems useful for determination of the absolute configuration of various types of organic molecules.

12.
J Org Chem ; 76(13): 5404-12, 2011 Jul 01.
Artigo em Inglês | MEDLINE | ID: mdl-21599007

RESUMO

A remarkable short preparation of desymmetrized bis-salphen scaffolds is presented. The protocol consists of an hydroxide-mediated hydrolysis of Lewis acidic bis-Zn(salphen) complexes yielding C(s)-symmetric diimine/amine salts that can be selectively transformed into bis-salphens with dissymmetric substitution patterns within each salphen unit under mild conditions. These isolated nonsymmetrical bis-salphen derivatives do not show signs of imine scrambling or decomposition due to a metal template effect. A possible rationale is provided for the formation and isolation of one of the intermediate bis-phenolate salts, and the hypothesis involves H-bond directed hydrolysis of the nearest located imine bond across the bis-salphen scaffold.

13.
Inorg Chem ; 50(17): 7934-6, 2011 Sep 05.
Artigo em Inglês | MEDLINE | ID: mdl-21806005

RESUMO

We describe a selective and template-controlled synthesis of a series of Zn(8) metal complexes based on a bis-nucleating salen ligand scaffold. Our results, a combination of X-ray analysis and solution studies, show that discrete, shape-persistent metal clusters can be prepared in high yield. Their activity in organic carbonate catalysis is a function of the metal-connecting fragment present in the exterior of the cluster complex. The high stability of the clusters has been confirmed by (1)H, (13)C (DEPTQ) and DOSY NMR, gel permeation chromatography, high-performance liquid chromatography, and mass spectrometry.

14.
Acta Crystallogr C ; 66(Pt 3): o147-50, 2010 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-20203413

RESUMO

The title compound, C(4)H(10)N(3)O(2)(+) x C(2)H(2)NO(3)(-) x C(2)H(3)NO(3), contains at least 11 distinct hydrogen-bond interactions showing a great variety of bond strengths. The shortest and strongest hydrogen bond [O...O = 2.5004 (12) A] is found between the uncharged oxamic acid molecule and the oxamate monoanion. The grouping formed by such a strong hydrogen bond can thus be considered as a hydrogen bis(oxamate) monoanion. It lacks crystallographic symmetry and the two oxamate groups have different conformations, showing an asymmetric hydrogen-bond interaction. Significantly, the asymmetry allows us to draw a direct comparison of site basicity for the two inequivalent carboxylate O atoms in the planar oxamate anion. The constituent molecular ions of (I) form ribbons, where all amide and carboxylate groups are coplanar. Graph-set analysis of the hydrogen-bonded networks reveals the R(2)(2)(10) and R(2)(2)(9) homodromic nets as important structure-directing motifs, which appear to be a common feature of many oxamate-containing compounds.


Assuntos
Ácido Oxâmico/análogos & derivados , Ácido Oxâmico/química , Cristalografia por Raios X , Ligação de Hidrogênio , Íons/química , Conformação Molecular , Estrutura Molecular
15.
ChemSusChem ; 12(13): 3152-3158, 2019 Jul 05.
Artigo em Inglês | MEDLINE | ID: mdl-30848531

RESUMO

Tertiary allylic alcohols were conveniently converted into either (Z)- or (E)-configured α,ß-unsaturated γ-amino acids by treatment with secondary amines under Pd catalysis at ambient conditions. The key to control the stereochemical course of these formal allylic aminations was the presence of a suitable diphosphine ligand, with dppp [1,3-bis(diphenylphosphino)propane, L12] providing high yields and selectivities for the (Z) isomers, whereas the bis[(2-diphenylphosphino)phenyl]ether (DPEPhos) derivative L1' allowed for selective formation of the corresponding (E) isomeric products. This ligand-controlled, stereodivergent protocol thus shows promise for the stereoselective preparation of allylic amine products from a common substrate precursor.


Assuntos
Aminoácidos/química , Paládio/química , Propanóis/química , Aminação , Catálise , Éteres/química , Ligantes , Fosfinas/química , Estereoisomerismo
16.
Dalton Trans ; 42(5): 1427-36, 2013 Feb 07.
Artigo em Inglês | MEDLINE | ID: mdl-23165945

RESUMO

The synthesis and characterization of nonsymmetrical octanuclear Schiff base clusters derived from nonsymmetrical diamine precursors is reported. These cluster complexes, typically assemblies comprising of four bimetallic salphen units, are isolated as a mixture of geometrical isomers as a result of different relative positions of the peripheral groups present in the diamine connectors within each cluster compound. A variety of peripheral groups can be installed including aryl bromides, protected carboxylic acids and pyridyl functionalities. The analysis of these octanuclear systems has been challenging, though mass spectrometric analysis provides a useful and diagnostic tool for the straightforward determination of the mono-disperse nature of these products. The presence of various electron-withdrawing and -donating groups on the peripheral aryl fragment allows for electronic modulation as supported by the application of these cluster derivatives in the homogeneous catalytic conversion of epoxides into their respective cyclic carbonates.

17.
Dalton Trans ; 42(21): 7595-603, 2013 Jun 07.
Artigo em Inglês | MEDLINE | ID: mdl-23535854

RESUMO

The use of the commercially available, bifunctional phosphine 1,3,5-triaza-7-phosphaadamantane (abbreviated as PN3) in conjunction with a series of Zn(salphen) complexes leads to sterically encumbered phosphine ligands as a result of (reversible) coordinative Zn-N interactions. The solid state and solution phase behaviour of these supramolecular ligand systems have been investigated in detail and revealed their stoichiometries in the solid state observed by X-ray crystallography, and those determined in solution by NMR and UV-Vis spectroscopy. Also, upon application of these supramolecular bulky phosphines in hydrosilylation catalysis employing 1-hexene as a substrate, the catalysis data infer the presence of an active Rh species with two coordinated, bulky PN3/Zn(salphen) assembly units having a maximum of three Zn(salphen)s associated per PN3 scaffold, with an excess of bulky phosphines hardly affecting the overall activity.

18.
Nat Commun ; 3: 785, 2012 Apr 17.
Artigo em Inglês | MEDLINE | ID: mdl-22510690

RESUMO

Self-assembly of large multi-component systems is a common strategy for the bottom-up construction of discrete, well-defined, nanoscopic-sized cages. Icosahedral or pseudospherical viral capsids, built up from hundreds of identical proteins, constitute typical examples of the complexity attained by biological self-assembly. Chemical versions of the so-called 5 Platonic regular or 13 Archimedean semi-regular polyhedra are usually assembled combining molecular platforms with metals with commensurate coordination spheres. Here we report novel, self-assembled cages, using the conical-shaped carboxylic acid derivatives of calix[4]arene and calix[5]arene as ligands, and the uranyl cation UO(2)2+ as a metallic counterpart, which coordinates with three carboxylates at the equatorial plane, giving rise to hexagonal bipyramidal architectures. As a result, octahedral and icosahedral anionic metallocages of nanoscopic dimensions are formed with an unusually small number of components.

19.
Dalton Trans ; 41(17): 5193-200, 2012 May 07.
Artigo em Inglês | MEDLINE | ID: mdl-22426506

RESUMO

The isolation and full characterization of multinuclear Schiff base complexes is reported, and their relevance as precursors for octanuclear Zn(8) salen cluster complex formation is discussed. Starting from simple precursors, three tetranuclear Zn(4) complexes were accessed that incorporate typical half-salen units and comprise of bridging acetates. The use of alternative reaction conditions or a step-wise approach smoothly leads to Zn(8) cluster formation. In addition, the tetranuclear Zn(4) complexes themselves may also serve as precursors toward Zn(8) cluster formation when treated under appropriate reaction conditions. The influence of the solvent medium in the latter Zn(4) → Zn(8) conversion was separately studied and revealed the formation of unusual pyridine-ligated multinuclear structures with fully condensed salen coordination pockets, providing a possible prelude to octanuclear cluster formation.

20.
Dalton Trans ; 41(32): 9766-72, 2012 Aug 28.
Artigo em Inglês | MEDLINE | ID: mdl-22782074

RESUMO

Tetra-Schiff bases derived from (chiral) bis-salphen ligand scaffolds furnish, upon metalation with appropriate metal reagents, their multinuclear structures with associated Zn(OAc)(2) or Zn(OH)(2) fragments. The tendency of retaining these salts was investigated using four different (chiral) bis-salphen scaffolds. The presence of the additional Zn ions was supported by NMR studies, mass determinations and X-ray crystallography showing in two cases the possible mode of coordination within these multinuclear structures. In one case, dimerization of the Zn(3) complex leads to a unique hexanuclear Zn(6) complex being a mixture of diastereoisomeric complexes as revealed by NMR spectroscopy.

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