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1.
J Am Chem Soc ; 137(45): 14406-22, 2015 Nov 18.
Artigo em Inglês | MEDLINE | ID: mdl-26542645

RESUMO

The syntheses, structures, and magnetic properties of four new complex salts, (PPN){[Mn(III)(salphen)(MeOH)]2[M(III)(CN)6]}·7MeOH (Mn2M·7MeOH) (M = Fe, Ru, Os and Co; PPN(+) = bis(triphenylphosphoranylidene)ammonium cation; H2salphen = N,N'-bis(salicylidene)-1,2-diaminobenzene), and a mixed metal Co/Os analogue (PPN){[Mn(III)(salphen)(MeOH)]2[Co(III)0.92Os(III)0.08(CN)6]}·7MeOH were undertaken. It was found that all compounds exhibit switchable single-molecule magnet (SMM) and exchange-bias behavior depending on the interstitial methanol content. The pristine (PPN){[Mn(salphen)(MeOH)]2[Os(CN)6]}·7MeOH (Mn2Os·7MeOH) behaves as an SMM with an effective barrier for the magnetization reversal, (Ueff/kB), of 17.1 K. Upon desolvation, Mn2Os exhibits an increase of Ueff/kB to 42.0 K and an opening of the hysteresis loop observable at 1.8 K. Mn2Os·7MeOH shows also exchange-bias behavior with magnetic hysteresis loops exhibiting a shift in the quantum tunneling to 0.25 T from zero-field. The Fe(III) and Ru(III) analogues were prepared as reference compounds for assessing the effect of the 5d versus 4d and 3d metal ions on the SMM properties. These compounds are also SMMs and exhibit similar effects but with lower energy barriers. These findings underscore the importance of introducing heavy transition elements into SMMs to improve their slow relaxation of the magnetization properties. The (PPN){[Mn(III)(salphen)(MeOH)]2[Co(III)(CN)6]}·7MeOH (Mn2Co·7MeOH) analogue with a diamagnetic Co(III) central atom and the mixed Co/Os (PPN){[Mn(III)(salphen)(MeOH)]2[Co(III)0.92Os(III)0.08(CN)6]}·7MeOH (Mn2Co/Os·7MeOH) "magnetically diluted" system with a 9:1 Co/Os metal ratio were prepared in order to further probe the nature of the energy barrier increase upon desolvation of Mn2Os. In addition, inelastic neutron scattering and frequency-domain Fourier-transform THz electron paramagnetic resonance spectra obtained on Mn2Os·7MeOH and Mn2Os in combination with the magnetic data revealed the presence of anisotropic exchange interactions between Mn(III) and Os(III) ions.

2.
Nanoscale ; 6(15): 8935-42, 2014 Aug 07.
Artigo em Inglês | MEDLINE | ID: mdl-24965378

RESUMO

Two different nickel precursors (NiCl2 or Ni(CH3COCH2COCH3)2) in the presence of 1-dodecanethiol and a mixture of oleylamine and oleic acid were used for a one-pot colloidal synthesis to produce high purity Ni3S4 nanoparticles with controlled shapes in high yields and narrow size distributions. By simply changing the nickel precursors, the shape of Ni3S4 nanocrystals can be readily tuned from triangular nanoprisms to tetrahedra (nanopyramids). The produced nanocrystals were characterized by transmission electron microscopy (TEM), energy-dispersive X-ray spectroscopy (EDS), X-ray powder diffraction, selected area electron diffraction, ultraviolet-visible spectroscopy and superconducting quantum interference device (SQUID). TEM tomography (3D-TEM) was employed to determine details of the particle shapes. SQUID measurements confirmed that particle shape and domain size could dramatically impact their magnetic properties, where tetrahedral nanopyramids of Ni3S4 nanoparticles showed ferromagnetic properties while the Ni3S4 nanoprisms showed random antiferromagnetic interactions between magnetic centers.

3.
Chemistry ; 20(25): 7593-7, 2014 Jun 16.
Artigo em Inglês | MEDLINE | ID: mdl-24807853

RESUMO

A family of magnetic metal-organic frameworks, (Ph3PMe)2[M2(TCNQ)3] {M=Fe(2+), Co(2+), Ni(2+) and Zn(2+)} have been prepared and structurally characterized. The honeycomb-like "layers" consist of M(II) ions doubly bridged with dinitrilomethane moieties of two 7,7,8,8-tetracyanoquinodimethane (TCNQ) dianions which are further connected through phenyl rings to form a 3D dianionic framework [M2TCNQ3](2-) with Ph3PMe(+) cations filling cavities that run along the c axis. Studies of the magnetic coupling through the TCNQ dianion in these structures revealed that it can promote long-range magnetic ordering despite the long coupling pathway.

4.
Dalton Trans ; 43(18): 6802-10, 2014 May 14.
Artigo em Inglês | MEDLINE | ID: mdl-24647575

RESUMO

Treatment of [Mn(dpop)(H2O)2]Cl2 (dpop = 2,13-dimethyl-3,6,9,12,18-pentaazabicyclo-[12.3.1]octadeca-1(18),2,12,14,16-pentaene) with K4[Mo(CN)7]·2H2O under varied synthetic conditions afforded four different compounds: {[Mn(dpop)]4[(dpop)Mn(H2O)]2[Mo(III)(CN)7]3·27H2O}n (1), {[(dpop)Mn(H2O)][Mo(III)(CN)7][Mn(dpop)]3[Mo(IV)(CN)8]·29H2O}n (2), {[(dpop)Mn(H2O)]2[Mo(IV)(CN)8]2[Mn(dpop)]4[Mo(III)(CN)7]·12H2O}n (3), and [(dpop)Mn(H2O)]2[Mo(IV)(CN)8]·9H2O (4). Compound 1 contains only [Mo(III)(CN)7](4-) anions and exhibits a corrugated two-dimensional layered architecture. The structure of 2 with a 1 : 1 ratio of Mo(III) : Mo(IV) is best described as a ladder-like chain composed of [Mo(III)(CN)7](4-)-based pentanuclear [Mo(III)Mn(II)4] fragments which are further linked by in situ produced [Mo(IV)(CN)8](4-) anions. In the case of 3, [Mn8Mo8] rings containing bent [Mo(III)Mn(II)2] fragments are extended into a two-dimensional layer with the ratio of [Mo(CN)7](4-) : [Mo(CN)8](4-) being 1 : 2. Compound 4 exhibits a bent trinuclear structure in which two CN(-) groups of [Mo(CN)8](4-) function as µ2-bridges to [Mn(dpop)(H2O)](2+) fragments. Magnetic studies suggest significant antiferromagnetic coupling interactions occur between Mo(III) and Mn(II) ions while, not surprisingly, interactions between the Mn(ii) ions through diamagnetic [Mo(IV)(CN)8](4-) anions are negligible. Compound 1 exhibits ferrimagnetic ordering below 3.0 K whereas 2 shows the signature of single molecule magnet behavior with slow relaxation of the magnetization and an effective energy barrier (U(eff)) of 8.1 K.

5.
Dalton Trans ; 42(41): 14693-701, 2013 Oct 01.
Artigo em Inglês | MEDLINE | ID: mdl-23943045

RESUMO

A series of isostructural octanuclear lanthanide complexes of general formula [Ln8(sao)4(µ3-OH)4(NO3)12(DMF)12] (Ln = Nd (), Sm (), Eu (), Gd (), Tb (), Dy (), Ho (), Er (); DMF = dimethylformamide) have been prepared via reactions of salicylaldoxime (saoH2), tetramethylammonium hydroxide (Me4NOH) with the appropriate lanthanide nitrate salt (Ln(NO3)3·6H2O). The metallic skeletons of the complexes describe [Ln4] tetrahedra encapsulated inside a [Ln4] square with the inner core stabilised through µ3-OH(-) ions and the periphery by µ4-sao(2-) ligands. The magnetic properties of compounds were investigated by dc and ac magnetometry. Temperature dependent ac magnetic susceptibility data reveal that the dysprosium analogue () displays an out-of-phase signal in the absence of an applied magnetic field indicative of slow relaxation of the magnetization typical of a Single-Molecule Magnet (SMM). Micro-SQUID measurements reveal temperature and sweep rate dependent hysteresis below 1.0 K.

6.
J Inorg Biochem ; 127: 175-81, 2013 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-23692703

RESUMO

Three new complexes of Cu(II) with 7-azaindole have been synthesized and characterized, a dicopper compound, [Cu(C7H5N2)2(H2O)]2·2CH3CN, 1, and two heptacopper compounds [Cu7(C7H5N2)6(µ3-OH)6(µ2-H2O)2(µ2-CH3OH)4](CH3COO)2·2C7H8·6CH3OH, 2, and [Cu7(C7H5N2)5(CH3COO)(µ3-OH)6(µ2-H2O)4(µ2-CH3OH)2](CH3COO)2, 4. The structure of 2 is monoclinic and it crystallizes in the P21/c space group: a=13.475(4)Å; b=12.945(4)Å; c=23.392(7)Å; ß=91.232(6)°. It contains a unique Cu7O12 core in which a central Cu(II) is situated at an inversion center and is bonded to 6 other Cu(II) ions via bridging oxygen atoms from OH(-), H2O, and CH3OH groups. Anionic 7-azaindole ligands bridge between adjacent outer Cu(II) ions and all Cu(II) ions have distorted octahedral coordination geometries. Variable temperature magnetic susceptibility measurements revealed the presence of antiferromagnetic exchange interactions between Cu(II) ions which leads to an S=5/2 ground state at 1.8K. Cytotoxicity and cell proliferation activities of the Cu compounds using human tongue squamous cell carcinoma and normal cells revealed that the compounds stimulated proliferation in both types of cells.


Assuntos
Complexos de Coordenação/química , Cobre/química , Indóis/química , Magnetismo , Linhagem Celular Tumoral , Proliferação de Células/efeitos dos fármacos , Complexos de Coordenação/farmacologia , Cristalografia por Raios X , Humanos , Indóis/farmacologia , Ligantes , Modelos Moleculares , Estrutura Molecular , Padrões de Referência
7.
J Am Chem Soc ; 135(10): 4040-50, 2013 Mar 13.
Artigo em Inglês | MEDLINE | ID: mdl-23414430

RESUMO

Hydrothermal reactions of copper(II) acetate, tetrazolate-5-carboxylate (tzc), and the neutral N-donor spacer ligand 1,3-di(4-pyridyl)propane (dpp) lead in a single reaction vial to the simultaneous formation of three different single-crystalline solvates [Cu(tzc)(dpp)]n·0.5C6H14·0.5H2O (1), [Cu(tzc)(dpp)]n·4.5H2O (2), and [Cu(tzc)(dpp)]n·1.25C6H14 (3). All three structures were characterized by single crystal X-ray diffraction. None of these solvates can be prepared as phase-pure bulk materials, but reaction conditions similar to those used for single crystal synthesis yield a phase-pure polycrystalline bulk material of an additional forth solvate phase [Cu(tzc)(dpp)]n·2H2O (4). Investigations of its thermal properties by in situ temperature-dependent synchrotron-based powder diffraction experiments have shown interesting phase transitions upon heating in a helium stream. Initially, the precursor dihydrate 4 transforms to an anhydrous phase [Cu(tzc)(dpp)]n (6I) via the intermediate monohydrate phase [Cu(tzc)(dpp)]n·H2O (5). Upon further heating, phase 6I transforms to a new anhydrous polymorph 6II, which transforms upon cooling to a further new phase 6III. Thermogravimetric measurements performed in tandem with differential scanning calorimetry as well as infrared spectroscopic investigations are in agreement with these findings. The de/resolvation behavior is accompanied by a dramatic change in their magnetic properties: The dihydrate phase shows antiferromagnetic exchange interactions, whereas ferromagnetic properties are observed for the trimorphic anhydrate system. This magnetic sponge-like behavior can be reversibly cycled upon de/resolvation of the material.


Assuntos
Compostos Ferrosos/química , Compostos Organometálicos/química , Temperatura , Cobre/química , Cristalografia por Raios X , Campos Magnéticos , Modelos Moleculares , Compostos Organometálicos/síntese química , Transição de Fase , Solventes/química
8.
Inorg Chem ; 52(4): 1670-2, 2013 Feb 18.
Artigo em Inglês | MEDLINE | ID: mdl-23350834

RESUMO

The reaction of 2-pyridylphosphonic acid (LH(2)) with iron(II) perchlorate and iron(III) nitrate afforded an interconnected, double-layered, cationic iron cage, [{Fe(36)L(44)(H(2)O)(48)}](20+) (1a), the largest interconnected, polynuclear ferric cage reported to date. Magnetic studies on 1a revealed antiferromagnetic coupling between the spins on adjacent Fe(III) ions.


Assuntos
Compostos Férricos/química , Nitratos/química , Organofosfonatos/química , Percloratos/química , Cristalografia por Raios X , Modelos Moleculares
11.
Dalton Trans ; 41(14): 3995-4006, 2012 Apr 14.
Artigo em Inglês | MEDLINE | ID: mdl-22362359

RESUMO

The use of a moderately hydrophobic ionic liquid, 1-butyl-2,3-dimethylimidazolium tetrafluoroborate ([BdMIM][BF(4)]), as a cosolvent with water, has been investigated in the synthesis of metal phosphonates. This hydro-ionothermal synthesis has been carried out through a systematic combinatorial investigation of several divalent metal chlorides and two related ligands, iminobis(methylphosphonic acid) and N-methyliminiobis(methylphosphonic acid). These reactions resulted in five new divalent metal phosphonates. We present here the synthetic techniques utilized as well as the X-ray structures and characteristic properties of each of these compounds. Co(HO(3)PCH(2)NH(2)CH(2)PO(3)H)(2), (1), consists of sheets that are hydrogen bonded together by pairs of P-O···H groups. Co(H(2)O)(2)(HO(3)PCH(2)NH(2)CH(2)PO(3)H)(2), (2), consists of chains that are connected through an extensive network of hydrogen bonds. Co(HO(3)PCH(2)NH(CH(3))CH(2)PO(3)H)(2), (3), is made up of sheets that are hydrogen bonded together by pairing P-O···H interactions. Zn(3)(O(3)PCH(2)NH(2)CH(2)PO(3))(2), (4), is isostructural to a previously reported cobalt compound which is a non-porous 3-dimensional network. CuClPO(3)CH(2)NH(2)CH(3), (5), formed as a result of an in situ N-C bond cleavage. Ladders built of Cu-O-P-O 8-membered rings are crosslinked by bridging chloride atoms to form sheets. 1, 3, 4 and 5 have been synthesized using the hydrophobic ionic liquid 1-butyl-2,3-dimethylimidazolium tetrafluoroborate ([BdMIM][BF(4)]) with water as a cosolvent, while 2 has been synthesized from identical conditions in the absence of the [BdMIM][BF(4)]. We also report the microwave assisted hydro-ionothermal synthesis of the known polymorph of 2, Co(H(2)O)(2)(HO(3)PCH(2)NH(2)CH(2)PO(3)H)(2), (6), synthesized in two hours providing high quality crystals in good yield. The compounds have been characterized by thermogravimetric analysis and IR spectroscopy, and their magnetic properties have been investigated.

12.
Dalton Trans ; 40(45): 12288-300, 2011 Dec 07.
Artigo em Inglês | MEDLINE | ID: mdl-21971918

RESUMO

The hydrothermal chemistry of a variety of M(II)SO(4) salts with the tetrazole (Ht) ligands 5,5'-(1,4-phenylene)bis(1H-tetrazole) (H(2)bdt), 5',5''-(1,1'-biphenyl)4,4'-diylbis(1H-tetrazole) (H(2)dbdt) and 5,5',5''-(1,3,5-phenylene)tris(1H-tetrazole) (H(3)btt) was investigated. In the case of Co(II), three phases were isolated, two of which incorporated sulfate: [Co(5)F(2)(dbdt)(4)(H(2)O)(6)]·2H(2)O (1·2H(2)O), [Co(4)(OH)(2)(SO(4))(bdt)(2)(H(2)O)(4)] (2) and [Co(3)(OH)(SO(4))(btt)(H(2)O)(4)]·3H(2)O (3·3H(2)O). The structures are three-dimensional and consist of cluster-based secondary building units: the pentanuclear {Co(5)F(2)(tetrazolate)(8)(H(2)O)(6)}, the tetranuclear {Co(4)(OH)(2)(SO(4))(2)(tetrazolate)(6)}(4-), and the trinuclear {Co(3)(µ(3)-OH)(SO(4))(2) (tetrazolate)(3)}(2-) for 1, 2, and 3, respectively. The Ni(II) analogue [Ni(2)(H(0.67)bdt)(3)]·10.5H(2)O (4·10.5H(2)O) is isomorphous with a fourth cobalt phase, the previously reported [Co(2)(H(0.67)bat)(3)]·20H(2)O and exhibits a {M(tetrazolate)(3/2)}(∞) chain as the fundamental building block. The dense three-dimensional structure of [Zn(bdt)] (5) consists of {ZnN(4)}tetrahedra linked through bdt ligands bonding through N1,N3 donors at either tetrazolate terminus. In contrast to the hydrothermal synthesis of 1-5, the Cd(II) material (Me(2)NH(2))(3)[Cd(12)Cl(3)(btt)(8)(DMF)(12)]·xDMF·yMeOH (DMF = dimethylformamide; x = ca. 12, y = ca. 5) was prepared in DMF/methanol. The structure is constructed from the linking of {Cd(4)Cl(tetrazolate)(8)(DMF)(4)}(1-) secondary building units to produce an open-framework material exhibiting 66.5% void volume. The magnetic properties of the Co(II) series are reflective of the structural building units.

14.
Inorg Chem ; 50(7): 2782-9, 2011 Apr 04.
Artigo em Inglês | MEDLINE | ID: mdl-21391549

RESUMO

Three members of the family of trigonal bipyramidal (TBP) complexes of general formula [M(tmphen)(2)](3)[M'(CN)(6)](2) (tmphen = 3,4,7,8-tetramethyl-1,10-phenanthroline) or [M(3)M'(2)], which are known to exhibit thermally induced spin crossover and charge transfer, have been investigated for optical and photomagnetic properties. The light-induced excited spin-state trapping (LIESST) effect found in classical spin crossover compounds, such as [Fe(phen)(2)(NCS)(2)], was explored for the [Fe(3)Fe(2)] and [Fe(3)Co(2)] compounds. Similarly, inspired by the light-induced charge-transfer properties of K(0.2)Co(1.4)[Fe(CN)(6)]·6.9H(2)O and related Prussian blue materials, the possibility of photo-induced magnetic changes was investigated for the [Co(3)Fe(2)] TBP complex. Optical reflectivity and magnetic susceptibility measurements were used to evaluate the photoactivity of these compounds. A comparison of these data before and after light irradiation demonstrates that (i) the spin crossover of the Fe(II) centers in the [Fe(3)Fe(2)] and [Fe(3)Co(2)] analogues and the (ii) charge transfer events in the [Co(3)Fe(2)] complex occur with temperature and irradiation. In addition, photomagnetic behavior is exhibited by all three compounds. The photo-conversion efficiency has been estimated at 20% of photo-induced high spin Fe(II) centers in [Fe(3)Co(2)], 30% of paramagnetic Co(II)-Fe(III) pairs in [Co(3)Fe(2)], and less than 2% of photo-induced high spin Fe(II) centers in [Fe(3)Fe(2)].


Assuntos
Luz , Nitrilos/química , Compostos Organometálicos/química , Cristalografia por Raios X , Modelos Moleculares , Compostos Organometálicos/síntese química
15.
J Am Chem Soc ; 132(38): 13123-5, 2010 Sep 29.
Artigo em Inglês | MEDLINE | ID: mdl-20809572

RESUMO

To expand the field of new cyanide materials of the 5d elements, we incorporated the [Os(CN)(6)](3-) anion into PB architectures in combination with the Co(II) cation. Herein, we report the first example of a photomagnetic PB analog containing Os(III) ions. In a similar vein as the prototypical CoFe PB analogs, this compound exhibits a wide variety of properties including Charge Transfer Induced Spin Transition (CTIST), Temperature Induced Excited Spin State Trapping (TIESST), and magnetic ordering.

16.
17.
Chem Commun (Camb) ; 46(25): 4484-6, 2010 Jul 07.
Artigo em Inglês | MEDLINE | ID: mdl-20464033

RESUMO

The trigonal bipyramidal molecules [M(tmphen)(2)](3)[Mo(CN)(6)](2).(solvent) (M = Co, Ni; tmphen = 3,4,7,8-tetramethyl-1,10-phenanthroline) based on the [Mo(III)(CN)(6)](3-) unit were prepared by loss of a cyanide ligand from [Mo(III)(CN)(7)](4-) and found to exhibit ferromagnetic interactions between the M(II) and Mo(III) centers.


Assuntos
Magnetismo , Molibdênio/química , Compostos Organometálicos/química , Ligantes , Modelos Moleculares , Compostos Organometálicos/síntese química
18.
Dalton Trans ; 39(18): 4341-52, 2010 May 14.
Artigo em Inglês | MEDLINE | ID: mdl-20422092

RESUMO

Reactions between trivalent rare earth ions (M(III) = La, Pr, Nd, Sm, Eu, Gd, Dy, Ho, Er and Yb) and the radical anion of 2,3,5,6-tetrafluoro-7,7,8,8-tetracyanoquinodimethane (TCNQF(4)) produce a family of mononuclear complexes {M[(TCNQF(4))](2)[H(2)O](x)}.(TCNQF(4))(3H(2)O), x = 6, 7. The cationic complex {M(III)([TCNQF(4)](-) )(2)[H(2)O](x)}(+) cocrystallizes with one [TCNQF(4)](-) radical anion and three water molecules. One of the coordinated [TCNQF(4)](-) radicals is involved in pi-pi stacking interactions with the uncoordinated [TCNQF(4)](-) radicals which leads to the antiferromagnetic coupling for these ((TCNQF(4))(2))(2-)pi-dimers. The second coordinated [TCNQF(4)](-) remains as a radical ligand and is not involved in pi-pi interactions. Magnetic studies indicate that the Sm compound magnetically orders at 4.4 K and that a fraction of the Gd and Dy samples undergo magnetic ordering at 3.7 K and 4.3 K respectively due to partial dehydration (loss of interstitial water molecules). Diamagnetic metal ions were used to generate magnetically dilute Gd, and Dy compounds that do not exhibit any signs of magnetic ordering.

19.
Dalton Trans ; 39(20): 4968-77, 2010 May 28.
Artigo em Inglês | MEDLINE | ID: mdl-20422113

RESUMO

Derivatives of the single molecule magnet (SMM) {[Re(triphos)(CN)(3)](4)[MnCl](4)} (Re(4)Mn(4)) {[Re(triphos)(CN)(3)](4)[Mn(CH(3)CN)](4)}(ClO(4))(4) (2) and {[Re(triphos)(CN)(3)](4)[Mn(ClO(4))](3)[Mn(CH(3)OH)(CH(3)O)]} (3), were prepared by reacting [Et(4)N][Re(triphos)(CN)(3)] (1) with Mn(ClO(4))(2)·6H(2)O. Reaction of sodium dicyanamide, NaN(CN)(2), with compound 2 in CH(2)Cl(2) results in the product {[Re(triphos)(CN)(3)](4)[Mn(N(CN)(2))](4)} (4), in which each Mn(II) site is terminated by a dicyanamide ligand. A similar reaction of compound 3 in CH(2)Cl(2)-MeOH solution with LiTCNQ (TCNQ = 7,7,8,8-tetracyanoquinodimethane) leads to the formation of {[Re(triphos)(CN)(3)](4)[Mn(TCNQ-TCNQ)(3)(Mn(HTCNQ)(CH(3)O))]} (5) whose structure is best described as a chain of dimers of Re(4)Mn(4) cubes bridged by sigma-bonded (TCNQ(2))(2-) linkers with one capping HTCNQ ligand.

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