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1.
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
2.
J Nanosci Nanotechnol ; 12(4): 3658-60, 2012 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-22849190

RESUMO

Understanding of mechanism of porous film formation is of fundamental importance for anodizing in general because, the onset of pore initiation terminates the barrier film growth process over the macroscopic metal surface. Several mechanisms have been proposed to explain pore formation. They include direct injection of aluminum ions into electrolyte and a field-assisted dissolution mechanism. High-resolution scanning electron microscopy of anodized surfaces and direct TEM of ion beam thinned films and ultrarmicrotomed film sections have been employed to gain further insight into the mechanism of initial porous film growth in 0.6 M oxalic acid. From detailed examination of the behavior of the xenon-tagged layer in the film during pore initiation and development in oxalic acid, the film structure of the barrier layer is found to be unstable during pore initiation and the instability of the film structure is possibly related to the field-assisted structure modification process.

3.
Inorg Chem ; 50(21): 10777-85, 2011 Nov 07.
Artigo em Inglês | MEDLINE | ID: mdl-21978029

RESUMO

Three one-dimensional coordination polymers [Mn(L)(N(3))](n) [L = L1 (1), L2 (2), L3 (3); L1H(2) = N,N'-bis(5-chlorosalicylideneiminato)-1,3-diaminopentane, L2H(2) = N,N'-bis(5-bromosalicylideneiminato)-1,3-diaminopentane, L3H(2) = N,N'-bis(5-bromosalicylideneiminato)-1,3-diamino-2-dimethylpropane] bridged by end-to-end azides were prepared. The crystal systems differ according to the Schiff bases used. Each Mn atom adopts a typical Jahn-Teller distortion. The helicity of the chains occurs in a racemic manner only for 2. No noncovalent forces are relevant in 2, while π-π contacts are visible in 1 and 3. Magnetic measurements show the presence of apparent spin canting. Complexes 1 and 3 exhibit a field-induced metamagnetic transition from an antiferromagnetic state to a weak ferromagnetic phase, whereas 2 embraces a field-induced two-step magnetic phase transition. The critical temperature is observed at 38 K for 2, which is relatively higher than those for 1 (11 K) and 3 (10 K). The pronounced long-range order may contribute from intrachain exchange couplings and through-space dipolar interactions between adjacent chains.

4.
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
5.
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
6.
Chemistry ; 17(10): 3028-34, 2011 Mar 01.
Artigo em Inglês | MEDLINE | ID: mdl-21284046

RESUMO

Three azide-bridged Mn(III) chains [Mn(3-MeOsalpn)(N(3))]⋅0.5 AClO(4) (A = Na (1), K (2), Rb (3); 3-MeOsalpn = N,N'-propylenebis(3-methoxysalicylideneiminato) dianion) incorporating alkali metal ions and perchlorate anions were systematically synthesized. The overall structure can be described as a one-dimensional chain bridged by end-to-end azide ligands, although spatial arrangements of Jahn-Teller axes of Mn in 1 and 2 are different from that in 3. Relying on the alkali metal ions, magnetic properties are varied from a two-step phase transition (1) to metamagnetic transitions (2 and 3). In this system, spin canting definitely plays a central role in giving rise to the apparent slow magnetic relaxations in 1 and 2 because application of a high external magnetic field tends to destroy single-chain magnet (SCM) properties. Despite the existence of a long-range antiferromagnetic order at T(N) , slow magnetic relaxation is notably observed in 2, which likely emanates from the operative spin canting below T(N) .

7.
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
8.
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
9.
Inorg Chem ; 48(19): 9066-8, 2009 Oct 05.
Artigo em Inglês | MEDLINE | ID: mdl-19739638

RESUMO

The reaction of [W(CN)(6)(bpy)](-) with the corresponding Mn Schiff bases led to the formation of two antiferromagnetic (1) and ferromagnetic (2) chains. The formation of the conglomerate (2) is associated with chiral induction by the enantiomeric chelate-ring conformation of the Mn Schiff base. Modulation of the linking groups in the Mn Schiff bases affects the interchain contacts, causing alteration of the magnetic behaviors from metamagnetism (1) to slow magnetic relaxation (2).

10.
Inorg Chem ; 48(13): 5617-9, 2009 Jul 06.
Artigo em Inglês | MEDLINE | ID: mdl-19492819

RESUMO

Cyanide-bridged M(V)-Mn(III) (M = Mo, W) bimetallic chain complexes with racemic spatial dispositions were constructed by self-assembling [M(CN)(8)](3-) precursors and Mn(III) Schiff bases. Antiferromagnetic couplings between spin centers within a chain result in a ferrimagnetic nature, and slow magnetic relaxations are observed as well.


Assuntos
Magnetismo , Metais/química , Ligação de Hidrogênio , Modelos Moleculares , Estrutura Molecular , Estereoisomerismo
11.
Chemistry ; 15(15): 3661-5, 2009.
Artigo em Inglês | MEDLINE | ID: mdl-19274695

RESUMO

Two-step magnetic transitions: An azide-bridged 1D Mn(III) coordination polymer with a unique single end-on mode was prepared; it displayed atypical antiferromagnetic couplings and field-induced two-step magnetic transitions (see figure). The spin-canted phenomenon in the antiferromagnetic chain complex plays a pivotal role in establishing the slow magnetic relaxation.

12.
Dalton Trans ; (11): 1954-61, 2009 Mar 21.
Artigo em Inglês | MEDLINE | ID: mdl-19259565

RESUMO

Three cyanide-linked Fe(iii)Mn(iii) bimetallic clusters, [(Tp)Fe(CN)(3)](2)[Mn(acphen)](2) [; acphen = N,N'-ethylenebis(2-hydroxyacetophenylideneiminato) dianion], [(Tp)Fe(CN)(3)](2)[Mn(5-Bracphen)](2) [; 5-Bracphen = N,N'-ethylenebis(5-bromo-2-hydroxyacetophenylideneiminato) dianion], and [(Tp)Fe(CN)(3)](2)[Mn(salen)](2).6H(2)O [; salen = N,N'-ethylenebis(salicylidineiminato) dianion], were prepared by self-assembling a facial [(Tp)Fe(CN)(3)](-) [Tp = hydrotris(pyrazolyl)borate] precursor and respective Mn(iii) Schiff bases. X-Ray crystal structure analyses revealed that each complex is composed of a central Mn(iii) dimer doubly linked by phenoxides of the tetradentate N(2)O(2) Schiff bases and the terminal [(Tp)Fe(CN)(3)](-) groups connecting to the center through cyanides. Using the spin Hamiltonian H = -2J(1)(S(Fe1).S(Mn1) + S(Mn1a).S(Fe1a)) - 2J(2)(S(Mn1).S(Mn1a)), where J(1) stands for the exchange coupling constant between Fe(iii) (S(Fe) = 1/2) and Mn(iii) (S(Mn) = 2) through cyanides and J(2) between Mn(iii) ions via phenoxides, the best fits corresponded to J(1) = 2.61 cm(-1) and J(2) = 0.85 cm(-1) for , J(1) = 2.50 cm(-1) and J(2) = 1.30 cm(-1) for , and J(1) = -2.15 cm(-1) and J(2) = 0.55 cm(-1) for . The phenoxide routes transmit ferromagnetic interactions in all cases, while ferromagnetic or antiferromagnetic couplings occur through the cyanide linkage. Although the geometric parameters relevant to the magnetic Fe-C[triple bond, length as m-dash]N-Mn pathways are analogous to each other their magnetic natures are varied across the compounds, which supports that a degree of orbital overlap is quite sensitive to a subtle structural change in the present system.


Assuntos
Cianetos/química , Compostos Férricos/química , Magnetismo , Manganês/química , Cristalografia por Raios X , Bases de Schiff/química
13.
Inorg Chem ; 48(3): 816-8, 2009 Feb 02.
Artigo em Inglês | MEDLINE | ID: mdl-19102632

RESUMO

A cyanide-linked Ru(III)(4d)-Mn(III)(3d) bimetallic chain complex (1) was prepared by the self-assembly of a ruthenium(III) bicyanide and a Mn(III) Schiff base. Ferromagnetic couplings between the magnetic centers are present within a chain, while antiferromagnetic interactions between chains (T(N) = 2.5 K) transmit. Complex 1 also shows a field-induced magnetic phase transition.

14.
Inorg Chem ; 47(22): 10214-6, 2008 Nov 17.
Artigo em Inglês | MEDLINE | ID: mdl-18947228

RESUMO

Assembling [W(CN) 6(bpy)] (-) and magnetic anisotropic Mn Schiff bases produced two Mn (III)(3d)-W (V)(5d) bimetallic chains. Modulation of the types and degrees of interchain pi-pi interactions in the one-dimensional coordination polymers leads to the variation of the magnetic behavior from a metamagnetic character to a single-chain magnet property.


Assuntos
Magnetismo , Manganês/química , Compostos Organometálicos/química , Tungstênio/química , 2,2'-Dipiridil/análogos & derivados , 2,2'-Dipiridil/química , Aminas/química , Anisotropia , Cianetos/química , Cicloexanos/química , Modelos Moleculares , Naftalenos/química , Compostos Organometálicos/síntese química
15.
Inorg Chem ; 46(21): 8481-3, 2007 Oct 15.
Artigo em Inglês | MEDLINE | ID: mdl-17850146

RESUMO

A new cyanide-bearing molecular precursor, mer-[Fe(pzcq)(CN)(3)]- (1), and a zigzag chain, [Fe(pzcq)(CN)(3)][Mn(salen)].4H(2)O (2), were prepared and characterized in terms of structure and magnetism. Magnetic data reveal that intrachain antiferromagnetic couplings via cyanide ligands in 2 are clearly operating, resulting in a ferrimagnetic nature.


Assuntos
Química Inorgânica/métodos , Ferricianetos/química , Ferro/química , Cristalografia por Raios X/métodos , Cianetos/análise , Compostos Férricos/química , Ligantes , Magnetismo , Conformação Molecular , Estrutura Molecular , Oscilometria , Temperatura
16.
Dalton Trans ; (20): 2070-6, 2007 May 28.
Artigo em Inglês | MEDLINE | ID: mdl-17502941

RESUMO

Two W(V)-Mn(III) bimetallic compounds, [Mn(Cl-salmen)(H(2)O)2]{[Mn(5-Clsalmen)(H(2)O)]2[W(CN)8].2H(2)O (1.2H(2)O) [5-Clsalmen = N,N'-(1-methylethylene)bis(5-chlorosalicylideneiminato) dianion], which contains trinuclear Mn(2)W and isolated Mn(III) moieties, and [Mn(3-MeOsalcy)(H(2)O)2]3[W(CN)(8)].2H(2)O (2.2H(2)O) [3-MeOsalcy = N,N'-(trans-1,2-cyclohexanediylethylene)bis(3-methoxysalicylideneiminato) dianion] molecules were prepared in redox processes and characterized using X-ray analysis and magnetic measurements. Compound 1 is composed of the {[Mn(5-Clsalmen)(H(2)O)]2[W(CN)8]}- trimer, in which two CN groups among eight in [W(CN)8](3-) bridge W(5+) and two Mn(3+) ions and the remaining CN ligands are hydrogen-bonded to water molecules or unbound, and the [Mn(Cl-salmen)(H(2)O)2]+ cation. Subsequently, two water molecules of the isolated cation are subject to hydrogen bonds. For 2, there are no covalent bonds among the subunits and six serial stacks of [Mn(3-MeOsalcy)(H(2)O)2]+ units are all hydrogen-bonded. The many hydrogen bonds found in both complexes eventually lead to three-dimensional networks. The magnetic studies for 1 reveal that antiferromagnetic interactions (J = -5.4 cm(-1)) between W(V) and Mn(III) centers within the trimer are transmitted via the bridging CN groups. Intermolecular antiferromagnetic couplings (zJ' = -0.2 cm(-1)) are also observed. The static and dynamic magnetic data of 1 demonstrate the existence of a field-induced spin-flop transition occurring among the clusters and monomeric molecules.


Assuntos
Cianetos/química , Compostos Férricos/química , Magnetismo , Manganês/química , Compostos Organometálicos/química , Bases de Schiff/química , Compostos de Tungstênio/química , Cátions , Ligação de Hidrogênio , Isomerismo , Estrutura Molecular , Oxirredução , Temperatura
17.
Inorg Chem ; 46(5): 1529-31, 2007 Mar 05.
Artigo em Inglês | MEDLINE | ID: mdl-17260983

RESUMO

A cyanide-bridged W-Co bimetallic complex (1) with a double-zigzag chain structure was characterized in terms of structure and magnetism. Compound 1 exhibits metamagnetism and spin canting induced by the presence of anisotropic CoII ions and noncovalent interactions.

18.
J Am Chem Soc ; 128(50): 15982-3, 2006 Dec 20.
Artigo em Inglês | MEDLINE | ID: mdl-17165720

RESUMO

Hybrid nanoparticles are of significant interest primarily because of their innate multifunctional capabilities. These capabilities can be exploited when hybrid nanoparticles are used for applications in the biomedical sciences in particular, where they are utilized as multimodal nanoplatforms for sensing, imaging, and therapy of biological targets. However, the realization of their biomedical applications has been difficult, in part because of a lack of high quality hybrid nanoparticles which possess high aqueous colloidal stability and biocompatibility while retaining their multifunctionalities. Here, we present the development of inorganic heterodimer nanoparticles of FePt-Au with multifunctional capabilities including catalytic growth effects, magnetic resonance (MR) contrast effects, optical signal enhancing properties, and high colloidal stability and biocompatibility. Their multimodal capabilities for biological detection are demonstrated through their utilizations in the patterned biochip based detection of avidin-biotin interaction as well as in molecular MR imaging of neuroblastoma cells.


Assuntos
Materiais Biocompatíveis/química , Técnicas Biossensoriais/métodos , Nanopartículas/química , Nanopartículas/ultraestrutura , Nanoestruturas/química , Nanoestruturas/ultraestrutura , Dimerização , Imagem por Ressonância Magnética , Microscopia Eletrônica de Transmissão
19.
Inorg Chem ; 45(24): 9613-5, 2006 Nov 27.
Artigo em Inglês | MEDLINE | ID: mdl-17112248

RESUMO

Two cyanide-bridged WV-M [M = Mn(II) (1), Co(II) (2)] bimetallic clusters were prepared by self-assembling a new molecular precursor [W(CN)6(bpy)]- and the corresponding metal complexes. Compound 1 shows a tetranuclear W2Mn2 entity, consisting of a Jahn-Teller ion, Mn(III), which serves as an anisotropic source, while compound 2 exhibits a trimeric W2Co structure. Among them, compound 1 displays slow relaxation of the magnetization, which is typical of a single-molecule magnet behavior.

20.
Inorg Chem ; 45(22): 8847-9, 2006 Oct 30.
Artigo em Inglês | MEDLINE | ID: mdl-17054339

RESUMO

Two manganese(III) azide complexes capped with tetradentate Schiff bases were characterized structurally and magnetically. The replacement of halogens on the Schiff bases leads to a drastic structural alteration from a dimer (1) bridged by phenoxide to a one-dimensional chain (2) linked by azide in a single end-to-end mode. Notably, magnetic studies of 2 show the concomitant existence of spin canting and metamagnetism.

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