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1.
Chembiochem ; 2020 Apr 13.
Artigo em Inglês | MEDLINE | ID: mdl-32282111

RESUMO

This paper reports the design, synthesis and cytotoxicity studies of two new isoxazole-derived aroylhydrazone ligands and their dinuclear copper(II) complexes. Compounds were fully characterized by various spectroscopic and analytical techniques. The molecular structures of four derivatives were confirmed by X-ray crystallography. The stability of the ligands and the complexes in aqueous medium was monitored spectroscopically. Both the ligands and the complexes were shown to interact with calf thymus DNA (ct-DNA). Additionally, structures containing a phenol pendant arm were significantly more cytotoxic than those carrying a pendant pyridine substituent, reaching sub-micromolar IC50 values on the triple-negative human breast cancer cell line MDA-MB-231. The metal chelation and transchelation ability of the compounds towards FeII , FeIII and ZnII ions was explored as a possible mechanism of action of these compounds.

2.
Artigo em Inglês | MEDLINE | ID: mdl-31943578

RESUMO

A mixed-valence {MnII 3 MnIII FeII 2 FeIII 2 } cyanide-bridged molecular cube hosting a caesium cation, Cs⊂{Mn4 Fe4 }, was synthesized and structurally characterized by X-ray diffraction. Cyclic-voltammetry measurements show that its electronic state can be switched between five different redox states, which results in a remarkable electrochromic effect. Magnetic measurements on fresh samples point to the occurrence of a spin-state change near room temperature, which could be ascribed to a metal-to-metal electron transfer converting the {FeII -CN-MnIII } pair into a {FeIII -CN-MnII } pair. This feature was only previously observed in the polymeric MnFe Prussian-blue analogues (PBAs). Moreover, this novel switchable molecule proved to be soluble and stable in organic solvents, paving the way for its integration into advanced materials.

3.
Chem Commun (Camb) ; 55(59): 8548-8551, 2019 Jul 18.
Artigo em Inglês | MEDLINE | ID: mdl-31268082

RESUMO

Benzene-1,3,5-tricarboxamide monomers derived from alkyl esters of tryptophan (BTA Trp) self-assemble into helices with an inner threefold hydrogen bond network surrounded by a second network involving the indole N-H groups. As a consequence of this extra stabilization of its helical assemblies, BTA Trp forms more viscous solutions than a range of ester and alkyl BTAs.

4.
Inorg Chem ; 58(5): 2930-2933, 2019 Mar 04.
Artigo em Inglês | MEDLINE | ID: mdl-30776219

RESUMO

A unique class of enantiopure N-heterocyclic carbene half-sandwich iridium complexes is reported. These compounds display stable configurations at the metal center, as demonstrated by their chiroptical properties. Remarkably, because of the nature of the naphthalimide molecule, two regioisomers containing five-membered [( R)-2a and ( S)-2a] and six-membered [( R)-2b and ( S)-2b] iridacycles were obtained. Density functional theory calculations are advanced to rationalize their relative stability.

5.
Inorg Chem ; 58(5): 3189-3195, 2019 Mar 04.
Artigo em Inglês | MEDLINE | ID: mdl-30762339

RESUMO

A novel synthetic procedure was set up to gain access to platinum coordination cages Pt2L4, which are less investigated compared to their palladium counterparts. This Pt2L4 nanocage exhibits an adequate cavity for guest encapsulation. Indeed, the Au(III) metal complex [Au(bdt)2]- (bdt = benzene-1,2-dithiolate) was successfully captured inside the cavity, in contrast to the analogous palladium cage which failed to host the gold complex. This result represents a rare example where a metal complex with thio-ligands can be encapsulated in a coordination cage. Moreover, it highlights the role of the metal center and the robustness of the platinum cage for host-guest chemistry. This discovery will inspire researchers in this area to pay more attention to Pt-cages. The host-guest system was fully characterized by NMR techniques and X-ray crystallographic analysis. Moreover, the nature of the host-guest interaction in this unique example was investigated and rationalized by DFT computational studies.

6.
J Am Chem Soc ; 140(50): 17632-17642, 2018 12 19.
Artigo em Inglês | MEDLINE | ID: mdl-30495946

RESUMO

The regio- and stereoselective addition of germanium and zinc across the C-C triple bond of nitrogen-, sulfur-, oxygen-, and phosphorus-substituted terminal and internal alkynes is achieved by reaction with a combination of R3GeH and Et2Zn. Diagnostic experiments support a radical-chain mechanism and the ß-zincated vinylgermanes that show exceptional stability are characterized by NMR spectroscopy and X-ray crystallography. The unique feature of this new radical germylzincation reaction is that the C(sp2)-Zn bond formed remains available for subsequent in situ Cu(I)- or Pd(0)-mediated C-C or C-heteroatom bond formation with retention of the double bond geometry. These protocols offer modular access to elaborated tri- and tetrasubstituted vinylgermanes decorated with heteroatom substituents ß to germanium that are useful for the preparation of stereodefined alkenes.

7.
Dalton Trans ; 47(10): 3440-3451, 2018 Mar 06.
Artigo em Inglês | MEDLINE | ID: mdl-29431779

RESUMO

A series of cyclometalated N-heterocyclic carbene complexes of the general formula [Ir(C^N)2(C^C:)] has been prepared. Two sets of compounds were designed, those where (C^C:) represents a bidentate naphthalimide-substituted imidazolylidene ligand and (C^N) = ppy (3a), F2ppy (4a), bzq (5a) and those where (C^C:) represents a naphthalimide-substituted benzimidazolylidene ligand and (C^N) = ppy (3b), F2ppy (4b), bzq (5b). The naphthalimide-imidazole and naphthalimide-benzimidazole ligands 1a,b and the related imidazolium and benzimidazolium salts 2a,b were also prepared and fully characterized. The N-heterocyclic carbene Ir(iii) complexes have been characterized by NMR spectroscopy, cyclic voltammetry and elemental analysis. Moreover, the molecular structures of one imidazolium salt and four Ir(iii) complexes were determined by single-crystal X-ray diffraction. The structures provide us with valuable information, most notably the orientation of the naphthalimide chromophore with respect to the N-heterocyclic carbene moiety. All compounds are luminescent at room temperature and in a frozen solvent at 77 K, exhibiting a broad emission band that extends beyond 700 nm. The presence of the naphthalimide moiety changes the character of the lowest excited state from 3MLCT to 3LC, as corroborated by DFT and TD-DFT calculations. Remarkably, replacing imidazole with a benzimidazole unit improves the quantum yields of these compounds by decreasing the knr values which is an important feature for optimized emission performance. These studies provide valuable insights about a novel class of N-heterocyclic carbene-based luminescent complexes containing organic chromophores and affording metal complexes emitting across the red-NIR range.

8.
Dalton Trans ; 46(31): 10240-10245, 2017 Aug 08.
Artigo em Inglês | MEDLINE | ID: mdl-28731087

RESUMO

Chiral two bladed complexes of [Co(L)2][BF4]2 (1) and [Zn(L)2][BF4]2 (2) containing an atropoisomeric semi-rigid bidentate ligand L were synthesized and characterized. They are obtained as homochiral species but in a racemic mixture via a ligand self-sorting mechanism. These enantiomers can be differentiated in solution using optically active anions.

9.
Anal Chem ; 89(3): 2155-2162, 2017 02 07.
Artigo em Inglês | MEDLINE | ID: mdl-28208266

RESUMO

Being able to easily determine the Cu(II) affinity for biomolecules of moderate affinity is important. Such biomolecules include amyloidogenic peptides, such as the well-known amyloid-ß peptide involved in Alzheimer's disease. Here, we report the synthesis of a new water-soluble ratiometric Cu(II) dye with a moderate affinity (109 M-1 at pH 7.1) and the characterizations of the Cu(II) corresponding complex by X-ray crystallography, EPR, and XAS spectroscopic methods. UV-vis competition was performed on the Aß peptide as well as on a wide series of modified peptides, leading to an affinity value of 1.6 × 109 M-1 at pH 7.1 for the Aß peptide and to a coordination model for the Cu(II) site within the Aß peptide that agrees with the one mostly accepted currently.


Assuntos
Peptídeos beta-Amiloides/metabolismo , Corantes/química , Cobre/metabolismo , Espectrofotometria Ultravioleta/métodos , Sequência de Aminoácidos , Peptídeos beta-Amiloides/química , Animais , Sítios de Ligação , Cristalografia por Raios X , Espectroscopia de Ressonância de Spin Eletrônica , Humanos , Concentração de Íons de Hidrogênio , Camundongos , Solubilidade , Água
10.
Dalton Trans ; 45(42): 16653-16660, 2016 Oct 25.
Artigo em Inglês | MEDLINE | ID: mdl-27778004

RESUMO

Polyoxometalate (POM) chemistry has recently offered excellent examples of single ion magnets (SIMs) and molecular spin qubits. Compared with conventional coordination compounds, POMs provide rigid and highly symmetric coordination sites. However, all POM-based SIMs reported to date exhibit a very limited range of possibilities for chemical processability. We present herein two new families of POM-based SIMs which are soluble in organic solvents: [Ln(ß-Mo8O26)2]5- {LnIII = Tb, Dy, Ho, Er, Tm and Yb} and the functionalised POMs [Ln{Mo5O13(OMe)4NNC6H4-p-NO2}2]3- {LnIII = Tb, Dy, Ho, Er, Yb and Nd}. In addition, these two families represent the first SIMs based on polyoxomolybdates. A magneto-structural analysis of these families is presented, which is based on an effective crystal field model, and compared with the results reported in analogous lanthanoid SIMs based on polyoxotungstates.

11.
Chem Commun (Camb) ; 52(91): 13369-13372, 2016 Nov 08.
Artigo em Inglês | MEDLINE | ID: mdl-27785504

RESUMO

A heterochiral 1,3,5-benzene tricarboxamide (BTA) monomer, derived from valine dodecyl ester, forms long rods in cyclohexane whilst its homochiral analogue assembles into dimers only at the same concentration. This highly original assembly behaviour is related to the destabilization of the dimeric structure containing the two heterochiral monomers as corroborated by a combined experimental and computational study.

12.
Angew Chem Int Ed Engl ; 55(36): 10712-6, 2016 08 26.
Artigo em Inglês | MEDLINE | ID: mdl-27504607

RESUMO

The reactivity of a stable copper(II) complex bearing fully oxidized iminobenzoquinone redox ligands towards nucleophiles is described. In sharp contrast with its genuine low-valent counterpart bearing reduced ligands, this complex performs high-yielding C-N bond formations. Mechanistic studies suggest that this behavior could stem from a mechanism akin to reductive elimination occurring at the metal center but facilitated by the ligand: it is proposed that a masked high oxidation state of the metal can be stabilized as a lower copper(II) oxidation state by the redox ligands without forfeiting its ability to behave as a high-valent copper(III) center. These observations are substantiated by a combination of advanced EPR spectroscopy techniques with DFT studies. This work sheds light on the potential of redox ligands as promoters of unusual reactivities at metal centers and illustrates the concept of masked high-valent metallic species.

13.
Org Lett ; 18(17): 4242-5, 2016 09 02.
Artigo em Inglês | MEDLINE | ID: mdl-27552360

RESUMO

Herein, the use of a well-defined low-valent cobalt(I) catalyst [HCo(PMe3)4] capable of performing the highly regio- and stereoselective hydrosilylation of internal alkynes is reported. The reaction can be applied to a variety of hydrosilanes, symmetrical and unsymmetrical alkynes, giving in many cases a single hydrosilylation isomer. Experimental and theoretical studies suggest the key step to be a hydro-cobaltation and that the reaction proceeds through a classical Chalk-Harrod mechanism.

14.
Chemistry ; 22(24): 8032-7, 2016 06 06.
Artigo em Inglês | MEDLINE | ID: mdl-27142245

RESUMO

A novel class of chiral luminescent square-planar platinum complexes with a π-bonded chiral thioquinonoid ligand is described. Remarkably the presence of this chiral organometallic ligand controls the aggregation of this square planar luminophor and imposes a homo- or hetero-chiral arrangement at the supramolecular level, displaying non-covalent Pt-Pt and π-π interactions. Interestingly these complexes are highly luminescent in the crystalline state and their photophysical properties can be traced to their aggregation in the solid state. A TD-DFT calculation is obtained to rationalize this unique behavior.

15.
Chem Commun (Camb) ; 52(41): 6785-8, 2016 May 21.
Artigo em Inglês | MEDLINE | ID: mdl-27104618

RESUMO

A 1,3-bis-diphenylphosphine allene can give rise to new coordination complexes with palladium, platinum and gold metals. These complexes were fully characterized by NMR, HRMS and X-ray diffraction analysis. For gold(i), the corresponding dinuclear complex has been used in a series of diagnostic catalytic reactions and gave promising preliminary results in asymmetric catalysis.


Assuntos
Alcenos/química , Complexos de Coordenação/química , Fosfinas/química , Catálise , Ligantes
16.
Dalton Trans ; 44(7): 2973-7, 2015 Feb 21.
Artigo em Inglês | MEDLINE | ID: mdl-25579845

RESUMO

A unique class of neutral cyclometalated platinum(ii) complexes with π-bonded benzenedithiolate are reported including two X-ray molecular structures. To the best of our knowledge these are the first structures to be reported for cyclometalated platinum complexes with a benzenedithiolate ligand. All of the complexes are luminescent in fluid solution at room temperature and in frozen solvent glasses at 77 K and their emission properties can be tuned through ligand variation.

17.
Chemistry ; 20(48): 15799-807, 2014 Nov 24.
Artigo em Inglês | MEDLINE | ID: mdl-25286882

RESUMO

The design and synthesis of switchable molecular tweezers based on a luminescent terpy(Pt-salphen)2 (1; terpy=terpyridine) complex is reported. Upon metal coordination, the tweezers can switch from an open "W"-shaped conformation to a closed "U"-shaped form that is adapted for selective recognition of cations. Closing of the tweezers by metal coordination (M=Zn(2+), Cu(2+), Pb(2+), Fe(2+), Hg(2+)) was monitored by (1)H NMR and/or UV/Vis titrations. During the titration, exclusive formation of the 1:1 complex [M(1)] was observed, without appearance of an intermediate 1:2 complex [M(1)2]. The crystallographic structure of the 1:1 complex was obtained with Pb(2+) and showed a distorted helical structure. Selective intercalation of Hg(2+) cations by the closed "U" form was observed. The tweezers were reopened by selective metal decoordination of the terpyridine ligand by using tris(2-aminoethyl)amine (tren) as a competitive ligand without modification of the Pt-salphen complex. Detailed photophysical studies were performed on the open and closed tweezers. Structured emission was observed in the open form from the Pt-salphen moieties, with a high quantum yield and a long lifetime. The emission is slightly modified upon closing with 1 equivalent of Zn(2+) or Hg(2+), whereas a dramatic quenching was obtained upon intercalation of additional Hg(2+).

18.
Inorg Chem ; 53(9): 4287-94, 2014 May 05.
Artigo em Inglês | MEDLINE | ID: mdl-24725008

RESUMO

A novel palladium-based metallacage was self-assembled. This nanocage displayed two complementary effects that operate in synergy for guest encapsulation. Indeed, a metal complex, [Pt(NO2)4](2-), was hosted inside the cavity, as demonstrated by solution NMR studies. Single-crystal X-ray diffraction shows that the guest adopts two different orientations, depending on the nature of the host-guest interactions involved. A density functional theory computational study is included to rationalize this type of host-guest interaction. These studies pave the way to a better comprehension of chemical interaction and transformation within confined nanospaces.

19.
Chemistry ; 20(19): 5795-801, 2014 May 05.
Artigo em Inglês | MEDLINE | ID: mdl-24668791

RESUMO

A new series of monoselenoquinone and diselenoquinone π complexes, [(η(6) -p-cymene)Ru(η(4) -C6 R4 SeE)] (R=H, E=Se (6); R=CH3 , E=Se (7); R=H, E=O (8)), as well as selenolate π complexes [(η(6) -p-cymene)Ru(η(5) -C6 H3 R2 Se)][SbF6 ] (R=H (9); R=CH3 (10)), stabilized by arene ruthenium moieties were prepared in good yields through nucleophilic substitution reactions from dichlorinated-arene and hydroxymonochlorinated-arene ruthenium complexes [(η(6) -p-cymene)Ru(C6 R4 XCl)][SbF6 ]2 (R=H, X=Cl (1); R=CH3 , X=Cl (2); R=H, X=OH (3)) as well as the monochlorinated π complexes [(η(6) -p-cymene)Ru(η(5) -C6 H3 R2 Cl)][SbF6 ]2 (R=H (4); R=CH3 (5)). The X-ray crystallographic structures of two of the compounds, [(η(6) -p-cymene)Ru(η(4) -C6 Me4 Se2 )] (7) and [(η(6) -p-cymene)Ru(η(4) -C6 H4 SeO)] (8), were determined. The structures confirm the identity of the target compounds and ascertain the coordination mode of these unprecedented ruthenium π complexes of selenoquinones. Furthermore, these new compounds display relevant cytotoxic properties towards human ovarian cancer cells.


Assuntos
Antineoplásicos/química , Antineoplásicos/síntese química , Complexos de Coordenação/química , Complexos de Coordenação/síntese química , Citotoxinas/química , Quinonas/química , Quinonas/síntese química , Rutênio/química , Linhagem Celular Tumoral , Cristalografia por Raios X , Feminino , Humanos , Espectroscopia de Ressonância Magnética , Estrutura Molecular , Neoplasias Ovarianas/tratamento farmacológico
20.
Angew Chem Int Ed Engl ; 53(7): 1987-91, 2014 Feb 10.
Artigo em Inglês | MEDLINE | ID: mdl-24453192

RESUMO

The first C3 -symmetric 44-core-valence-electron triangular palladium clusters, [{(SAr')(PAr3 )Pd}3 ](+) , have been synthesized by activation of the CS bond of isothioureas. Owing to delocalized metal-metal bonding, these stable complexes are the first noble-metal analogues of the π-aromatic cyclopropenyl cation [C3 H3 ](+) , with their all-metal aromaticity involving d-type atomic orbitals.

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