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1.
Dalton Trans ; 47(3): 845-851, 2018 Jan 15.
Artigo em Inglês | MEDLINE | ID: mdl-29250623

RESUMO

MII (M = Mn, Ni) coordination frameworks, singly linked by end-on azide ligands, were prepared by employing the long, flexible spacer ligand, p-XBP4. These two-dimensional layer structures underwent reversible crystal-to-amorphous phase transformations during the hydration-dehydration process. Moreover, the magnetic nature changes from antiferromagnetic to ferromagnetic coupling when moving from Mn to Ni.

2.
Inorg Chem ; 56(9): 4911-4917, 2017 May 01.
Artigo em Inglês | MEDLINE | ID: mdl-28414438

RESUMO

Controlling the coordination sphere of lanthanoid complexes is a challenging critical step toward controlling their relaxation properties. Here we present the synthesis of hexacoordinated dysprosium single-molecule magnets, where tripodal ligands achieve a near-perfect octahedral coordination. We perform a complete experimental and theoretical investigation of their magnetic properties, including a full single-crystal magnetic anisotropy analysis. The combination of electrostatic and crystal-field computational tools (SIMPRE and CONDON codes) allows us to explain the static behavior of these systems in detail.

3.
Dalton Trans ; 45(48): 19416-19427, 2016 Dec 06.
Artigo em Inglês | MEDLINE | ID: mdl-27882362

RESUMO

We synthesized six Fe(iii)-Mn(iii) bimetallic compounds by self-assembling the newly developed mer-Fe cyanide PPh4[Fe(Clqpa)(CN)3]·H2O (1) and PPh4[Fe(Brqpa)(CN)3]·H2O (2) with Mn Schiff base Mn(5-Xsalen)+ cations. These compounds include [Fe(Xqpa)(CN)3][Mn(5-Ysalen)]·pMeOH·qH2O [qpaH2 = N-(quinolin-8-yl)picolinamide; salen = N,N'-ethylenebis(salicylideneiminato) dianion; X = Cl, Y = H (3); X = Cl, Y = Br (4); X = Br, Y = H (5); X = Br, Y = F (6); X = Br, Y = Cl (7); X = Br, Y = Br (8)]. When precursor 1 was used, compounds 3 and 4 were isolated to give a dinuclear entity and a linear chain structure, respectively. The reaction of precursor 2 with the Schiff bases afforded four linear Fe(iii)-Mn(iii) chain complexes. Chain chirality with P- and M-helicity emerges in 4, 7, and 8, while 5 exhibits chain helicity opposite to the previous chain complexes and 6 presents no chain helicity. Such a structural feature is heavily dependent on the interchain π-π contacts and the Fe precursor bridging unit. Chiral induction from a local ethylenediamine link of Y-salen is propagated over the chain via noncovalent π-π interactions. All the bimetallic compounds show antiferromagnetic interactions transmitted by the cyanide linkage. A field-induced metamagnetic transition is involved in 4, 7, and 8, while a field-induced two-step transition is evident in 6. From a magnetostructural viewpoint, the coupling constant is primarily governed by the Mn-Nax-Cax angle (ax = axial) in the bimetallic chain complexes composed of mer-Fe(iii) tricyanides, although the torsion angle plays a role.

4.
Health Phys ; 107(3): 200-5, 2014 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-25068957

RESUMO

The authors have developed and evaluated a new method that uses transit dose in the treatment room in verification of dose delivery to patients. Five intensity modulated radiotherapy (IMRT) plans were selected from actual cancer patients, and transit dose was measured using MapCHECK 2 and an anthropomorphic phantom. The criteria used as a verification tool for the dose delivery to the patient were gamma-index-based dose comparison between the computed dose and measured dose. When the doses were delivered to an anthropomorphic phantom normally, the average passing rate was 95.2% based on a gamma index analysis. This feasibility study suggested that transit dose-based quality assurance can provide information about the accuracy of an inhomogeneity correction algorithm and patient positioning during treatment, allowing its use as a verification tool for actual dose delivery to patients in the treatment room.


Assuntos
Doses de Radiação , Planejamento da Radioterapia Assistida por Computador/métodos , Radioterapia de Intensidade Modulada/métodos , Estudos de Viabilidade , Humanos , Neoplasias/radioterapia , Imagens de Fantasmas , Radiometria , Dosagem Radioterapêutica
5.
Dalton Trans ; 43(19): 6994-7, 2014 May 21.
Artigo em Inglês | MEDLINE | ID: mdl-24705865

RESUMO

Dehydration of the three-dimensional Cu(II)-Mn(III) coordination network undergoes a dramatic magnetic phase transformation from a paramagnetic state to a long-range magnetic ordered phase with glassy behavior. The gas adsorption behavior and re-entrant spin glass character are uniquely apparent in the dehydrated sample.


Assuntos
Complexos de Coordenação/química , Cobre/química , Magnetismo , Manganês/química , Compostos Orgânicos/química , Desidratação , Etilenodiaminas/química , Porosidade , Temperatura
6.
Inorg Chem ; 52(15): 8677-84, 2013 Aug 05.
Artigo em Inglês | MEDLINE | ID: mdl-23855908

RESUMO

Five one-dimensional bimetallic W(V)Mn(III) complexes 1-5, consisting of [W(CN)6(bpy)](-) anions and [Mn(Schiff base)](+) cations, were prepared. The central coordination geometry around each W atom is determined as a distorted dodecahedron (DD) for 1 and 2, and a distorted square antiprism (SAPR) for 3-5. Magnetic analyses demonstrate that compounds 1, 4, and 5 exhibit antiferromagnetic interactions between magnetic centers, which are different from the ferromagnetic couplings in 2 and 3. For the distorted DD geometry, the Mn-N(ax) (ax = axial) bond length increases when moving from 1 to 2, with the Mn-N(ax)-C(ax) angle remaining constant. The elongation of the bond length is responsible for the reduction in orbital overlap and consequent ferromagnetic coupling in 2. In comparison, for 3-5 with the distorted SAPR geometry, given that the Mn-N(ax) bond lengths are similar across all the samples, the increase in the Mn-N(ax)-C(ax) angles accounts for the enhanced magnetic strength. Notably, a correlation between structure and magnetic exchange coupling is established for the first time in W(V)Mn(III) bimetallic systems based on the [W(CN)6(bpy)](-) precursor.


Assuntos
Fenômenos Magnéticos , Manganês/química , Nitrilos/química , Compostos Organometálicos/química , Tungstênio/química , Modelos Moleculares , Conformação Molecular , Compostos Organometálicos/síntese química
7.
Dalton Trans ; 42(19): 7204-9, 2013 May 21.
Artigo em Inglês | MEDLINE | ID: mdl-23525365

RESUMO

Isostructural tetranuclear clusters [Ln4(salen)6]·xH2O [Ln = Dy, 1·5.5H2O; Ho, 2·4.6H2O; Eu, 3·5.2H2O; salen = N,N'-ethylenebis(salicylideneiminato)dianion] were prepared by self-assembling the corresponding lanthanide ions and a quadridentate Schiff base. Interestingly, the Ln ions are surrounded by the N- and O-donors of the Schiff bases, leading to seven- and eight-coordinate environments. The heptacoordinated Ln centers adopt a distorted capped trigonal prism, while the octacoordinated Ln atoms are in a dodecahedral disposition. The Dy complex exhibits slow magnetic relaxation, characteristic of a single-molecule magnet. Two relaxation modes in the Dy system are evident when H(dc) = 1.4 kG is applied, which is attributable to the existence of the dissimilar coordination geometries around Dy. In comparison, the Ho and Eu analogues were magnetically inspected, displaying no typical slow magnetic relaxation. These findings elucidate that the metal component in the system plays a central role in the occurrence of the magnetization relaxation process. The pronounced long-range order may contribute to intrachain exchange couplings and through-space dipolar interactions between adjacent chains.


Assuntos
Complexos de Coordenação/síntese química , Elementos da Série dos Lantanídeos/química , Magnetismo , Complexos de Coordenação/química , Cristalografia por Raios X , Disprósio/química , Etilenodiaminas/química , Európio/química , Hólmio/química , Conformação Molecular , Bases de Schiff/química , Temperatura
8.
Dalton Trans ; 42(16): 5796-804, 2013 Apr 28.
Artigo em Inglês | MEDLINE | ID: mdl-23450248

RESUMO

Three tetranuclear clusters [(Tp(Me,mt3))Fe(CN)3Mn(L)]2 (1, L = 5-Clacphmen; 2, L = 5-Clsalen; 3, L = 5-MeOsalen; Tp(Me,mt3) = hydrotris(3-methyl-4,5-propylene-5-methylpyrazol-1-yl)borate) were prepared by assembling the fac-Fe tricyanide with the corresponding Mn Schiff bases. The assembled molecules are linked by cyanide and phenoxide bridges. Weak π-π contacts between molecules are evident in these clusters. Compounds 1-3 exhibit slow relaxation of the magnetization. The phenoxide linkers mediate ferromagnetic coupling between the Mn centers, which is ascribed to the long axial Mn-O* length. The overall magnetic exchange coupling nature of the Fe-C≡N-Mn route is accounted for by the important structural parameters of bridging pathways such as Mn-N(cyano) length, Mn-N(cyano)-C(cyano) angle, and C(eq)-Fe···Mn-N(eq) (eq = equatorial) torsion angle.


Assuntos
Complexos de Coordenação/síntese química , Cianetos/química , Compostos Férricos/química , Manganês/química , Complexos de Coordenação/química , Cristalografia por Raios X , Íons/química , Magnetismo , Conformação Molecular , Bases de Schiff/química
9.
Chem Commun (Camb) ; 49(23): 2329-31, 2013 Mar 21.
Artigo em Inglês | MEDLINE | ID: mdl-23403976

RESUMO

An aqua-bridged Mn metal-organic framework was prepared, and a dramatic structural transformation occurs upon solvent exchange-resolvation and desolvation-resolvation processes. The desolvated phase, formed by removing the aqua bridges, exhibits selective CO(2) uptake over N(2), H(2), and CH(4). Further, antiferromagnetic couplings are also found between Mn spins in the secondary building units.


Assuntos
Dióxido de Carbono/química , Gases/química , Manganês/química , Adsorção , Complexos de Coordenação/química , Hidrogênio/química , Metano/química , Conformação Molecular , Nitrogênio/química , Polímeros/química
10.
Chemistry ; 18(37): 11541-4, 2012 Sep 10.
Artigo em Inglês | MEDLINE | ID: mdl-22887038

RESUMO

Crystal clear: An end-on (EO) azide-bridged Co(II) layer (see scheme; 1) with coordinated water molecules, long spacer p-XBP4 ligands, and unbound azide anions was evacuated to generate a dehydrated sample of 2. A reversible crystal-to-amorphous structural transformation accompanied by color and magnetic changes takes place between 1 and 2 by using a desolvation-solvation protocol.


Assuntos
Azidas/química , Cobalto/química , Cor , Campos Magnéticos , Compostos Organometálicos/química , Modelos Moleculares , Estrutura Molecular , Compostos Organometálicos/síntese química , Temperatura
11.
Chem Commun (Camb) ; 48(59): 7404-6, 2012 Jul 28.
Artigo em Inglês | MEDLINE | ID: mdl-22713966

RESUMO

A tetranuclear Fe(III)(2)Mn(III)(2) compound was prepared using highly blocked precursors. The well-isolated molecular entity associated with appropriate magnetic anisotropy allows for single-molecule magnet behavior.


Assuntos
Cianetos/química , Compostos Férricos/química , Imãs/química , Manganês/química , Estrutura Molecular , Bases de Schiff/química
12.
Chem Commun (Camb) ; 48(19): 2519-21, 2012 Mar 04.
Artigo em Inglês | MEDLINE | ID: mdl-22281795

RESUMO

A tetranuclear Er(III) compound chelated with N(2)O(2) donors of a tetradentate Schiff base was produced from the self-assembly of the corresponding chemical species. This intriguing cluster shows field-induced slow relaxation of magnetization.


Assuntos
Érbio/química , Fenômenos Magnéticos , Compostos Organometálicos/química , Etilenodiaminas/química , Modelos Moleculares , Conformação Molecular , Compostos Organometálicos/síntese química
13.
Dalton Trans ; 41(6): 1776-85, 2012 Feb 14.
Artigo em Inglês | MEDLINE | ID: mdl-22159090

RESUMO

Five Fe(III)Mn(III) bimetallic compounds [Fe(iqc)(CN)(3)][Mn(5-Xsalen)]·pMeOH·qMeCN·rH(2)O [Hiqc = N-(quinolin-8-yl)isoquinoline-1-carboxamide; salen = N,N'-ethylenebis(salicylideneiminato) dianion; X = H(2), F(3, 3a), Cl(4), Br(5)] were prepared by assembling a newly designed mer-Fe tricyanide (Ph(4)P)[Fe(iqc)(CN)(3)]·0.5H(2)O (1) and the respective Mn Schiff bases Mn(5-Xsalen)(+). Compounds 2-4 show linear chain structures in which trans-positioned cyanides of the Fe precursor bridge neighbouring Mn atoms, while 5 is a zigzag chain coordination polymer where two cyanide groups of the precursor in the cis mode act as bridges. The structural change from linear to zigzag may arise from the size effect of the halogens. The reversible structural transformation occurs between 3 and 3a upon the solvation-desolvation protocol and the corresponding magnetic behaviours are affected. Furthermore, in 4 and 5, the helical chains are established through hydrogen bonding of solvent molecules. From a magnetostructural point of view, within the linear chain system, the ferromagnetic coupling in 2, contrary to antiferromagnetic interactions in 3-4, is associated with the large torsion angle of C(eq)-Fe-Mn-N(O)(eq) (eq = equatorial) as well as almost the linear Mn-N≡C angle.


Assuntos
Compostos Férricos/química , Ferricianetos/química , Imãs/química , Manganês/química , Bases de Schiff/química , Cristalografia por Raios X , Compostos Férricos/síntese química , Ferricianetos/síntese química , Modelos Moleculares , Estrutura Molecular , Bases de Schiff/síntese química
14.
Inorg Chem ; 50(22): 11306-8, 2011 Nov 21.
Artigo em Inglês | MEDLINE | ID: mdl-22013958

RESUMO

A 5d-3d bimetallic compound was prepared by self-assembling [W(CN)(8)](3-) and the Mn(III) Schiff bases. This neutral complex consists of cyanide-linked W(V)Mn(III) anionic chains and isolated Mn(III) Schiff base cations. We demonstrate that two types of relaxation processes are involved in the system; the low-T dynamics may come from magnetic domain dynamics and the high-T relaxation stems from the anionic chain, revealing single-chain magnet character.


Assuntos
Cianetos/química , Imãs/química , Manganês/química , Tungstênio/química , Modelos Moleculares , Conformação Molecular , Bases de Schiff/química
15.
Chem Commun (Camb) ; 47(37): 10416-8, 2011 Oct 07.
Artigo em Inglês | MEDLINE | ID: mdl-21833431

RESUMO

A 1D Mo(V)Mn(III) chain compound balanced by {Fe[HC(3,5-Me(2)pz)(3)](2)}(2+) dications was prepared. This complex displays a typical single-chain magnet character associated with the Mo(V)Mn(III) chain and a spin crossover phenomenon arising from cationic Fe(II) subunits. The spin crossover behavior tends to slightly affect single-chain magnetic properties at low temperature.


Assuntos
Ferro/química , Imãs/química , Manganês/química , Molibdênio/química , Nitrilos/química , Compostos Organometálicos/química , Modelos Moleculares , Conformação Molecular , Temperatura
16.
Inorg Chem ; 50(5): 1749-57, 2011 Mar 07.
Artigo em Inglês | MEDLINE | ID: mdl-21192714

RESUMO

Three two-dimensional (2D) layered M(III)-Cu(II) (M = Fe, Cr) bimetallic complexes and a discrete cluster were prepared using [M(CN)(6)](3-) and respective Cu macrocycles with methyl (1, 3) or ethyl (2, 4) side groups. The crystal structures can be described as aesthetic honeycomb-like M(2)Cu(3) neutral sheets (1, 3, 4) and a pentanuclear Fe(2)Cu(3) entity (2) with an isolated Cu(L2)(2+) moiety. The steric hindrance induced by the pendant groups renders the internal parameters of the Cu-N(ax) (where the "ax" subscript denotes axial) length and Cu-N(ax)-C(ax) angle to become elongated and acute. The magnetic data disclose that ferromagnetic couplings are transmitted between M(III) and Cu(II) ions through the CN links. For 4, particularly, there is a magnetically defined chain (J(c)) composed of dimers (J(d)) and trimers (J(t)), based on the structural considerations. The intramolecular magnetic coupling constants are J(d) = 3.73 cm(-1) and J(t) = 4.08 cm(-1), while the J(c) value corresponds to 0.17 cm(-1). From a magnetostructural point of view, it is reasoned that the Cu-N(ax) bond length is probably a determining factor of the strength of magnetic couplings in 4.

17.
Biochem Biophys Res Commun ; 404(2): 638-45, 2011 Jan 14.
Artigo em Inglês | MEDLINE | ID: mdl-21146501

RESUMO

To investigate the in vivo functions of normal prion protein (PrP) in Drosophila, we utilized characterized transgenic flies expressing ³(F)4-tagged mouse PrP (Mo-PrP³(F)4). The neurotoxicity of pathogenic Machado-Joseph Disease (MJD) glutamine (Q) 78 and 127Q proteins were enhanced by the co-expression of Mo-PrP³(F)4in the fly eyes, while the eyes of controls flies and flies expressing Mo-PrP³(F)4) alone or together with MJD-Q27 or 20Q proteins did not show any defect. Susceptibilities to H2O2, paraquat, and Dithiothreitol (DTT) were altered in Mo-PrP³(F)4 flies. In addition, Mo-PrP³(F)4 flies were significantly more susceptible to the perturbation of autophagy signaling by an autophagy inhibitor, 3-methyladenine (3-MA), and inducer, LiCl. Taken together, our data suggest that Mo-PrP³(F)4 may enhance the neurotoxicity of pathogenic Poly-Q proteins by perturbing oxidative and autophagy signaling.


Assuntos
Autofagia , Drosophila melanogaster/metabolismo , Doença de Machado-Joseph/metabolismo , Neurônios/metabolismo , Peptídeos/metabolismo , Príons/metabolismo , Adenina/análogos & derivados , Adenina/toxicidade , Animais , Animais Geneticamente Modificados/genética , Animais Geneticamente Modificados/metabolismo , Modelos Animais de Doenças , Ditiotreitol/toxicidade , Drosophila melanogaster/genética , Olho/embriologia , Olho/metabolismo , Cloreto de Lítio/toxicidade , Doença de Machado-Joseph/patologia , Camundongos , Modelos Genéticos , Neurônios/efeitos dos fármacos , Neurônios/patologia , Estresse Oxidativo , Paraquat/toxicidade , Príons/genética , Resposta a Proteínas não Dobradas , Água/farmacologia
18.
Chem Commun (Camb) ; 46(46): 8779-81, 2010 Dec 14.
Artigo em Inglês | MEDLINE | ID: mdl-20963213

RESUMO

A Co(II)-Cu(II) framework based on a paramagnetic metalloligand [Co(Tt)(2)] shows a permanent porosity with a record high surface area for magnetic MOFs as well as a reversible magnetic transformation between a paramagnetic-like state and a short-range magnetic order in the low-temperature regime upon solvation-desolvation cyclings.


Assuntos
Boratos/química , Cobalto/química , Cobre/química , Magnetismo , Compostos Organometálicos/química , Triazóis/química , Adsorção , Ligantes , Modelos Moleculares , Porosidade , Temperatura
19.
Inorg Chem ; 49(11): 4723-5, 2010 Jun 07.
Artigo em Inglês | MEDLINE | ID: mdl-20450205

RESUMO

Isostructural lanthanide-organic frameworks were prepared by a solvothermal reaction of the corresponding metal ions and the phosphine-oxide-based tricarboxylate ligand. The gravimetric gas uptake was unexpectedly increased when going from Nd(3+) to Gd(3+), which is associated with the enhanced surface areas and electrostatic interactions between exposed metal ions and gas molecules with quadrupole moments.


Assuntos
Elementos da Série dos Lantanídeos/química , Compostos Organometálicos/química , Adsorção , Sítios de Ligação , Modelos Moleculares , Estrutura Molecular , Compostos Organometálicos/síntese química , Tamanho da Partícula , Porosidade , Propriedades de Superfície
20.
Inorg Chem ; 49(10): 4632-42, 2010 May 17.
Artigo em Inglês | MEDLINE | ID: mdl-20402476

RESUMO

Reaction of [(Tp)Fe(CN)(3)](-) [Tp = hydrotris(pyrazolyl)borate] with respective Mn(III) Schiff bases led to the formation of four dimeric molecules, [(Tp)Fe(CN)(3)][Mn(1-napen)(H(2)O)].MeCN.4H(2)O [1; 1-napen = N,N'-ethylenebis(2-hydroxy-1-naphthylideneiminato) dianion], [(Tp)Fe(CN)(3)][Mn(5-Clsalen)(H(2)O)] [2; 5-Clsalcy = N,N'-(trans-1,2-cyclohexanediylethylene)bis(5-chlorosalicylideneiminato) dianion], [(Tp)Fe(CN)(3)][Mn(2-acnapen)(MeOH)].MeOH [3; 2-acnapen = N,N'-ethylenebis(1-hydroxy-2-acetonaphthylideneiminato) dianion], [(Tp)Fe(CN)(3)][Mn(3-MeOsalen)(H(2)O)] [4; 3-MeOsalen = N,N'-ethylenebis(3-methoxysalicylideneiminato) dianion], and a one-dimensional (1D) zigzag chain [(Tp)Fe(CN)(3)][Mn(2-acnapen)].H(2)O (5). The dimers contain multiple intermolecular interactions such as hydrogen bonds, face-to-face pi-pi contacts, and edge-to-face CH-pi forces, raising molecular dimensions from one-dimensional (1D) up to three-dimensional (3D) arrays, whereas there are no pi-pi stacking interactions in the 1D chain compound. Magnetic measurements reveal that ferromagnetic couplings are obviously operative between Mn(III) and Fe(III) spin centers transmitted by CN bridges for 1-3 and 5, and antiferromagnetic interactions are however unexpectedly present in 4. On the basis of the proper spin Hamiltonians, magnetic exchange couplings are estimated to be in the span from 1.79 to 7.48 cm(-1) for the ferromagnetically coupled systems and -1.40 cm (-1) for the antiferromagnetic dimer. A slow magnetic relaxation is tangible in 5, which is in connection with isolated chains devoid of any intermolecular noncovalent interactions. Density Functional Theory (DFT) calculations and comparison of structural parameters suggest that the observed magnetic behaviors are mainly associated with the bending of the Mn-N[triple bond]C angle in the bridging pathway.


Assuntos
Ferro/química , Magnetismo , Manganês/química , Nitrilos/química , Compostos Organometálicos/química , Teoria Quântica , Modelos Moleculares , Conformação Molecular , Compostos Organometálicos/síntese química , Bases de Schiff/química
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