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1.
Chem Commun (Camb) ; 56(57): 7893-7896, 2020 Jul 21.
Artigo em Inglês | MEDLINE | ID: mdl-32524101

RESUMO

The reaction of the bis(methoxy)-2-pyridyl-phosphine (MeO)2P(2-py) (1) with [Ni(MeCN)6](BF4)2 leads to the unexpected single-step reduction of NiII and the formation of a tetrahedral nickel(0) complex [{(MeO)2P(2-py-H)}2{(MeO)2P(2-py)}2Ni](BF4)2 (2). The redox activity is probably induced by the decomposition of the tetrafluoroborate anion; NMR spectroscopic studies point towards a fluoride-assisted oxidation of the 2-pyridyl-phosphine ligand, with associated reduction of the metal.

2.
Dalton Trans ; 2020 Apr 03.
Artigo em Inglês | MEDLINE | ID: mdl-32242884

RESUMO

The coordination characteristics and donor/acceptor properties of a series of 2-pyridyl substituted phosphine ligands have been investigated using structural, spectroscopic and DFT calculational studies. A range of different coordination modes are observed in Mo and W carbonyl complexes of tris-2-pyridyl-phosphine ligands of the type P(2-py') (2-py' = substituted or unsubstituted 2-pyridyl group), including an unprecedented example exhibiting N,N',µ2-π coordination. DFT calculations were used to assess the relative donor/acceptor properties of a range of related 2-pyridyl-phosphine ligands with respect to PPh3 and PtBu3.

3.
Inorg Chem ; 2020 Apr 24.
Artigo em Inglês | MEDLINE | ID: mdl-32330014

RESUMO

A series of new tris(2-pyridyl) bismuthine ligands of the type [Bi(2-py')3] have been prepared, containing a range of substituents at various positions within their pyridyl rings (py'). They can act as intact ligands or, as a result of the low C-Bi bond energy, exhibit noninnocent reactivity in the presence of metal ions. Structural studies of Li+ and Ag+ complexes show that the coordination to metal ions using their pyridyl-N atoms and to anions using the Lewis acidity of their Bi(III) centers can be modified by the presence of substituents within the 2-pyridyl rings, especially at the 6- or 3-positions, which can block the donor-N or Lewis acid Bi sites. Electron withdrawing groups (like CF3 or Br) can also severely reduce their ability to act as ligands to metal ions by reducing the electron donating ability of the pyridyl-N atoms. Noninnocent character is found in the reactions with Cu+ and Cu2+, resulting in the coupling of pyridyl groups to form bipyridines, with the rate of this reaction being dependent on the anion present in the metal salts. This leads to the formation of Bi(III)/Cu(I) complexes containing hypervalent [X2Bi(2-R-py)]- (X = Cl, Br) anions. Alternatively, the tris(2-pyridyl) bismuthine ligands can act as 2-pyridyl transfer reagents, transferring 2-py groups to Au(I) and Fe(II).

4.
J Org Chem ; 85(7): 4918-4926, 2020 Apr 03.
Artigo em Inglês | MEDLINE | ID: mdl-32153183

RESUMO

An octapodal corannulene-based supramolecular system has been prepared by introducing eight corannulene moieties in a porphyrin scaffold. Despite the potential of this double picket fence porphyrin for double-tweezer behavior, NMR titrations show exclusive formation of 1:1 adducts. The system exhibits very strong affinity for C60 and C70 (K1 = (2.71 ± 0.08) × 104 and (2.13 ± 0.1) × 105 M-1, respectively), presenting selectivity for the latter. Density functional theory (DFT) calculations indicate that, in addition to the four corannulene units, the relatively flexible porphyrin tether actively participates in the recognition process, resulting in a strong synergistic effect. This leads to a very strong interaction with C60, which in turn also induces a large structural change on the other face (second potential binding site), leading to a negative allosteric effect. We also introduced Zn2+ in the porphyrin core in an attempt to modulate its flexibility. The resulting metalloporphyrin also displayed single-tweezer behavior, albeit with slightly smaller binding constants for C60 and C70, suggesting that the effect of the coordination of fullerene to one face of our supramolecular platform was still transmitted to the other face, leading to the deactivation of the second potential binding site.

5.
Dalton Trans ; 48(47): 17544-17555, 2019 Dec 03.
Artigo em Inglês | MEDLINE | ID: mdl-31748774

RESUMO

In the study presented herein, we explore the ability of copper complexes with coordinated pyridine-2-carboxaldehyde (pyca) or 2-acetylpyridine (acepy) ligands to promote the addition of amines (Schiff condensation) and other nucleophiles such as alcohols (hemiacetal formation). Distinct reactivity patterns are observed: unlike pyca complexes, acepy copper complexes can promote self-aldol addition. The introduction of a flexible chain via Schiff condensation with ß-alanine allows the possibility of chelate ring ring-opening processes mediated by pH. Further derivatization of the complex [CuCl(py-2-C(H)[double bond, length as m-dash]NCH2CH2COO)] is possible by replacing its chloride ligand with different pseudohalogens (N3-, NCO- and NCS-). In addition to the change in their magnetism, which correlates with their solid-state structures, more unexpected effects in their cytotoxicity and relaxitivities are observed, which determines their possibility to be used as MRI contrast agents. The replacement of a chloride by another pseudohalogen, although a simple strategy, can be used to critically change the cytotoxicity of the Schiff base copper(ii) complex and its selectivity towards specific cell lines.


Assuntos
Complexos de Coordenação/química , Complexos de Coordenação/toxicidade , Cobre/química , Cobre/toxicidade , Animais , Células CHO , Linhagem Celular , Proliferação de Células/efeitos dos fármacos , Sobrevivência Celular/efeitos dos fármacos , Complexos de Coordenação/síntese química , Cricetulus , Relação Dose-Resposta a Droga , Humanos , Cetonas/química , Cetonas/farmacologia , Ligantes , Modelos Moleculares , Estrutura Molecular , Piridinas/química , Piridinas/farmacologia , Relação Estrutura-Atividade , beta-Alanina/química , beta-Alanina/farmacologia
6.
Chemistry ; 25(61): 14003-14009, 2019 Nov 04.
Artigo em Inglês | MEDLINE | ID: mdl-31469199

RESUMO

The systematic assembly of supramolecular arrangements is a persistent challenge in modern coordination chemistry, especially where further aspects of complexity are concerned, as in the case of large molecular mixed-metal arrangements. One targeted approach to such heterometallic complexes is to engineer metal-based donor ligands of the correct geometry to build 3D arrangements upon coordination to other metals. This simple idea has, however, only rarely been applied to main group metal-based ligand systems. Here, we show that the new, bench-stable tris(3-pyridyl)stannane ligand PhSn(3-Py)3 (3-Py=3-pyridyl) provides simple access to a range of heterometallic SnIV /transition metal complexes, and that the presence of weakly coordinating counter anions can be used to build discrete molecular arrangements involving anion encapsulation. This work therefore provides a building strategy in this area, which parallels that of supramolecular transition metal chemistry.


Assuntos
Complexos de Coordenação/química , Metais/química , Polímeros/química , Compostos de Estanho/química , Cristalografia por Raios X , Ligantes , Conformação Molecular , Estanho/química
7.
Dalton Trans ; 48(17): 5692-5697, 2019 Apr 23.
Artigo em Inglês | MEDLINE | ID: mdl-30968911

RESUMO

Post-functionalisation of the aluminate anion [EtAl(6-R-2-py)3]- (6-R-2-py = 6-R-2-pyridyl, R = Me or Br) can be accomplished via nucleophilic addition of the pyridyl groups to the electrophilic C[double bond, length as m-dash]O group of aldehydes (RCH[double bond, length as m-dash]O) or by deprotonation of carboxylic acids (RCO2H). NMR spectroscopic and crystallographic studies show how 6-Me-2-py groups can detect chirality and reveal a new aspect of isomerism.

8.
J Org Chem ; 84(10): 6183-6190, 2019 May 17.
Artigo em Inglês | MEDLINE | ID: mdl-30993988

RESUMO

The incorporation of eight pyrene units in a single porphyrin core exhibits a great synergistic effect, resulting in high affinity toward C60 and C70. This octapyrene porphyrin is easily accessible by a straightforward two-step synthetic approach that involves an octuple Suzuki reaction. The new supramolecular platform can present single- or double-tweezer fullerene hosting behavior. The switch from double- to single-tweezer behavior is triggered by the simple coordination of Zn2+ to the porphyrin. Both the octapyrene porphyrin 2HPOP and its zinc metalloporphyrin analogue ZnPOP show very high affinity for C60 and C70, while simultaneously allowing the discrimination of C70 over C60 in a C60/C70 mixture. The use of 2HPOP and ZnPOP for the enrichment of real fullerene mixtures is also demonstrated.

9.
J Org Chem ; 84(2): 840-850, 2019 01 18.
Artigo em Inglês | MEDLINE | ID: mdl-30596238

RESUMO

The thiol-Michael addition (TMA) is a powerful methodology to click several fragments together, despite having been underestimated in the synthesis of complex systems for supramolecular chemistry. Herein, a very fast and efficient method has been developed to make covalent molecular capsules by taking advantage of the TMA click reaction. Several scaffolds commonly used in supramolecular chemistry, such as calixarenes, CTV, or cavitands, have been used to quickly obtain covalent cages. Additionally, a ' click&click' procedure has been also developed, by sequential combination of TMA and CuAAC click reaction, as an easy and quick way to build complex molecular structures.

10.
Chemistry ; 24(64): 17019-17026, 2018 Nov 16.
Artigo em Inglês | MEDLINE | ID: mdl-30092123

RESUMO

Postfunctionalization of the aluminate anion [EtAl(6-Me-2-py)3 ]- (1) (2-py=2-pyridyl) with alkoxide ligands can be achieved by the selective reactions of the lithium salt 1 Li with alcohols in the appropriate stoichiometry. This method can be used to introduce 3- and 4-py functionality in the form of 3- and 4-alkoxymethylpyridyl groups, while maintaining the integrity of the aluminate framework, thereby giving entry to new supramolecular chemistry. Chirality can be introduced either by using a chiral alcohol as a reactant or by the stepwise reaction of 1 Li with two different nonchiral alcohols. The latter route has allowed the synthesis of a rare example of a chiral-at-aluminium aluminate.

11.
Dalton Trans ; 47(20): 7036-7043, 2018 May 22.
Artigo em Inglês | MEDLINE | ID: mdl-29741181

RESUMO

Difficulties in the preparation of neutral ligands of the type [RSi(2-py)3] (where 2-py is an unfunctionalised 2-pyridyl ring unit) have thwarted efforts to expand the coordination chemistry of ligands of this type. However, simply switching the pyridyl substituents to 6-methyl-pyridyl groups (6-Me-2-py) in the current paper has allowed smooth, high-yielding access to the [PhSi(6-Me-2-py)3] ligand (1), and the first exploration of its coordination chemistry with transition metals. The synthesis, single-crystal X-ray structures and solution dynamics of the new complexes [{PhSi(6-Me-2-py)3}CuCH3CN][PF6], [{PhSi(6-Me-2-py)3}CuCH3CN][CuCl2], [{PhSi(6-Me-2-py)3}FeCl2], [{PhSi(6-Me-2-py)3}Mo(CO)3] and [{PhSi(6-Me-2-py)3}CoCl2] are reported. The paramagnetic Fe2+ and Co2+ complexes show strongly shifted NMR resonances for the coordinated pyridyl units due to large Fermi-contact shifts. However, magnetic anisotropy also leads to considerable pseudo-contact shifts so that both contributions have to be included in the paramagnetic NMR analysis.

12.
Angew Chem Int Ed Engl ; 57(22): 6648-6652, 2018 05 28.
Artigo em Inglês | MEDLINE | ID: mdl-29603844

RESUMO

Although a multitude of studies have explored the coordination chemistry of classical tripodal ligands containing a range of main-group bridgehead atoms or groups, it is not clear how periodic trends affect ligand character and reactivity within a single ligand family. A case in point is the extensive family of neutral tris-2-pyridyl ligands E(2-py)3 (E=C-R, N, P), which are closely related to archetypal tris-pyrazolyl borates. With the 6-methyl substituted ligands E(6-Me-2-py)3 (E=As, Sb, Bi) in hand, the effects of bridgehead modification alone on descending a single group in the periodic table were assessed. The primary influence on coordination behaviour is the increasing Lewis acidity (electropositivity) of the bridgehead atom as Group 15 is descended, which not only modulates the electron density on the pyridyl donor groups but also introduces the potential for anion selective coordination behaviour.

13.
Dalton Trans ; 47(7): 2232-2239, 2018 Feb 13.
Artigo em Inglês | MEDLINE | ID: mdl-29363698

RESUMO

The coordination ability of tris(pyridyl)aluminates can be modified by the steric and electronic character of substituents at the 6-positions of their pyridyl rings. Whereas [EtAl(6-Me-2-py)3]- (1) coordinates strongly to lanthanide(ii) ions [Eu(ii) and Yb(ii)], [EtAl(6-Br-2-py)3]- (2) forms much weaker complexes, and [EtAl(6-CF3-2-py)3]- does not coordinate at all. The modification of the donor ability of these ligands is investigated by solid-state studies of the Ln(ii) sandwich compounds and by competitive coordination studies in solution.

14.
Inorg Chem ; 57(1): 264-276, 2018 Jan 02.
Artigo em Inglês | MEDLINE | ID: mdl-29227100

RESUMO

CuCl2·2H2O and Cu(ClO4)2·6H2O are able to promote aldol addition of pyridine-2-carboxaldehyde (pyca) with acetone, acetophenone, or cyclohexenone under neutral and mild conditions. The general and simple one-pot procedure for the aldol addition to Cu(II) complexes accesses novel Cu complexes with a large variety of different structural motifs, from which the aldol-addition ligand can be liberated by treatment with NH3. Neutral heteroleptic complexes in which the ligand acts as bidentate, or homoleptic cationic complexes in which the ligand acts as tridentate can be obtained depending on the copper salt used. The key step in these reactions is the coordination of pyca to copper, which increases the electrophilic character of the aldehyde, with Cu(ClO4)2 leading to a higher degree of activation than CuCl2, as predicted by DFT calculations. A regio- and stereoselective double aldol addition of pyca in the reaction of Cu(ClO4)2·6H2O with acetone leads to the formation of a dimer copper complex in which the novel double aldol addition product acts as a pentadentate ligand. A possible mechanism is discussed. The work is supported by extensive crystallographic studies.

15.
Chemistry ; 24(8): 2013-2019, 2018 Feb 06.
Artigo em Inglês | MEDLINE | ID: mdl-29214680

RESUMO

Oxidation of the PIII dianion [S-P(µ-NtBu)]22- (1) with elemental sulphur, selenium and tellurium gives the PV dianions [(S)(E)P(µ-NtBu)]22- (E = S (6 a), Se (6 b), Te (6 c)). Although 6 c proves to be too unstable, the S,S-dianion 6 a and ambidentate S,Se-dianion 6 b are readily transferred intact to main group and transition metal elements, producing a range of new cage and coordination compounds. While their coordination characteristics are in many ways similar to closely-related isoelectronic phosph(V)azane anions [(E)(RN=)P(µ-NtBu)]22- , the sterically unhindered nature of 6 introduces an expanded range of coordination modes, that is, facial S,S- and Se,Se-bonding as well as side-on S,Se-coordination. All of these bonding modes are observed for the amibidentate S,Se dianion 6 b.

16.
Chemistry ; 24(13): 3073-3082, 2018 Mar 02.
Artigo em Inglês | MEDLINE | ID: mdl-29205953

RESUMO

Outside the confines and well-established domain of organic chemistry, the systematic building of large macromolecular arrangements based on non-carbon elements represents a significant and exciting challenge. Our aim in the past two decades has been to develop robust synthetic methods to construct new types of main group architectures in a methodical way, principles of design that parallel those used in the organic arena. This Concept article addresses the fundamental thermodynamic and kinetic problems involved in the design and synthesis of main group macrocycles and looks to future developments of macromolecules in this area, as well as new applications in coordination chemistry.

17.
Dalton Trans ; 46(38): 12775-12779, 2017 Oct 14.
Artigo em Inglês | MEDLINE | ID: mdl-28926065

RESUMO

The unsymmetric PIII/PV cyclodiphosphazane framework [(S[double bond, length as m-dash])(H)P(µ-NtBu)2PNHtBu] (2) provides entry into the mixed chalgogenide dianion [(S)P(µ-NtBu)2P(Se)NtBu]2-, and unique insight into the mechanisms of cis/trans isomerism in phosph(iii)- and phosph(v)-azanes.

18.
Angew Chem Int Ed Engl ; 56(31): 9087-9090, 2017 07 24.
Artigo em Inglês | MEDLINE | ID: mdl-28429494

RESUMO

Inorganic macrocycles, based on non-carbon backbones, present exciting synthetic challenges in the systematic assembly of inorganic molecules, as well as new avenues in host-guest and supramolecular chemistry. Here we demonstrate a new high-yielding modular approach to a broad range of trimeric and hexameric S- and Se-bridged inorganic macrocycles based on cyclophosphazane frameworks, using the building blocks [S=(H)P(µ-NR)]2 . The method involves the in situ generation of the key intermediate [E....._ (S....._ )P(µ-NR)]22- (E=S, Se) dianion, which can be reacted with electrophilic [ClP(µ-NR)]2 to give PIII /PV hexameric rings or reacted with I2 to give trimeric PV variants. Important issues which are highlighted in this work are the competitive bridging ability of S versus Se in these systems and the synthesis of the first air-stable and chiral inorganic macrocycles.

19.
Dalton Trans ; 46(13): 4287-4295, 2017 Mar 27.
Artigo em Inglês | MEDLINE | ID: mdl-28280831

RESUMO

The influence of paramagnetic Ln3+ ions on the NMR behaviour is investigated via a series of new isostructural lanthanide-containing cages with the general formula [LnTi6O3(OiPr)9(salicylate)6] (Ln-1, Ln = La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho and Er). Compared to conventional coordination compounds containing Ln3+ ions, the peripheral ligands in Ln-1 are separated from the paramagnetic lanthanide centres by oxo-Ti4+ linkages, and therefore experience a weaker paramagnetic influence. As a result, all of the 1H and 13C NMR signals of these Ln-1 cages (except for Gd-1) are observed and can be unambiguously assigned, which provides an excellent platform for the in-depth study of the NMR behaviour of paramagnetic Ln3+ ions. Further analysis of the fully assigned paramagnetic signals suggests that the pseudo-contact component dominates the 1H NMR shifts, whereas both the pseudo-contact and Fermi-contact contributions affect the 13C shifts, although the majority of the resonance environments are at least four bonds distant from the central Ln3+ ion. Our results also show that the use of Bleaney's factors to describe the pseudo-contact shift is inadequate for this Ln-1 cage series.

20.
Chem Commun (Camb) ; 53(7): 1225-1228, 2017 Jan 19.
Artigo em Inglês | MEDLINE | ID: mdl-27966697

RESUMO

Here we illustrate a new method for the rapid determination of ee's of chiral alcohols using the thermally-stable, non-chiral lithium aluminate reagent [EtAl(6-Me-2-py)3Li] (1). In situ reaction of the alcohols with 1 produces robust dimers in solution, present as diastereomeric pairs (SS/RR and RS) with distinct resonances in their 1H and 7Li NMR spectra. The ee can be calculated simply from integration of the 1H and/or 7Li NMR spectra.

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