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1.
J Am Chem Soc ; 142(2): 931-936, 2020 Jan 15.
Artigo em Inglês | MEDLINE | ID: mdl-31880442

RESUMO

A one-dimensional coordination solid 1c is synthesized by reaction of a bispyridyl dithienylethene (DTE) photochromic unit with the highly anisotropic dysprosium-based single-molecule magnet [Dy(Tppy)F(pyridine)2]PF6. Slow magnetic relaxation characteristics are retained in the chain compound 1c, and photoisomerization of the bridging DTE ligand induces a single-crystal-to-single-crystal transformation that can be monitored using photocrystallography. Notably, the resulting chain compound 1o exhibits faster low-temperature relaxation than that of 1c, which is apparent in magnetic hysteresis data collected for both compounds as high as 4 K. Ab initio calculations suggest that this photomodulation of the magnetic relaxation behavior is due to crystal packing changes rather than changes to the crystal field splitting upon ligand isomerization.

2.
Inorg Chem ; 55(14): 7020-5, 2016 Jul 18.
Artigo em Inglês | MEDLINE | ID: mdl-27367598

RESUMO

An original cationic water-soluble cyclen-based Eu(III) complex [EuL(1)](+) featuring a chromophore-functionalized antenna to increase the two-photon (2P) absorption properties was synthesized. The photophysical properties were thoroughly studied in various solvents and rationalized with the help of theoretical calculations. The complex exhibits an optimized 2P absorption cross section. Finally, 2P microscopy imaging experiments on living T24 human cancer cells highlighted the spontaneous internalization and the biological stability of this 2P bioprobe in vitro. Macrocyclic-based antennas open new perspectives for future optimization of the photophysical properties and allows envisaging the design of Eu, Tb, Yb, and Sm bioprobes. This result also opens the way for the design of functional two-photon Ln complexes able to monitor intracellular physicochemical parameters.


Assuntos
Elementos da Série dos Lantanídeos/metabolismo , Sondas Moleculares/metabolismo , Cátions , Microscopia/métodos
3.
Inorg Chem ; 54(14): 6891-9, 2015 Jul 20.
Artigo em Inglês | MEDLINE | ID: mdl-26125503

RESUMO

The gradual magnetostructural transition in breathing crystals based on copper(II) and pyrazolyl-substituted nitronyl nitroxides has been analyzed by means of DDCI quantum chemistry calculations. The magnetic coupling constants (J) within the spin triads of Cu(hfac)2L(Bu)·0.5C8H18 have been evaluated for the X-ray structures reported at different temperatures. The coupling is strongly antiferromagnetic at low temperature and becomes ferromagnetic when the temperature increases. The intercluster magnetic coupling (J') is antiferromagnetic and shows a marked dependence on temperature. The magnetostructural transition can be reproduced using the calculated J values for each structure in the simulation of the magnetic susceptibility. However, the µ(T) curve can be improved nicely by considering the coexistence of two phases in the transition region, whose ratio varies with temperature corresponding to both the weakly and strongly coupled spin states. These results complement a recent VT-FTIR study on the parent Cu(hfac)2L(Pr) compound with a gradual magnetostructural transition.

4.
J Phys Chem A ; 116(13): 3465-73, 2012 Apr 05.
Artigo em Inglês | MEDLINE | ID: mdl-22404104

RESUMO

The performance of recent density functionals for computation of molecular magnetic coupling constants (J) in hydrogen-bonded systems is evaluated. A survey of six Cu(II) dinuclear complexes is considered. The global accuracy trend is GGAs

Assuntos
Cobre/química , Magnetismo , Compostos Organometálicos/química , Teoria Quântica , Ligação de Hidrogênio
5.
J Chem Theory Comput ; 5(6): 1506-10, 2009 Jun 09.
Artigo em Inglês | MEDLINE | ID: mdl-26609844

RESUMO

The exchange coupling in a structuraly characterized Cu(II)2 complex is analyzed to highlight the role of H bonds in the generation of efficient magnetic interactions. The interest for complementary insights which are not accessible through DFT calculations (Desplanches, C. et al. J. Am. Chem. Soc. 2002, 124, 5197) has driven this state-of-the-art ab initio inspection. The wave function expansion based upon localized orbitals allows us to selectively turn on specific mechanisms and quantitatively evaluate their roles in the exchange interactions. Our singlet-triplet splitting calculations demonstrate the enhancement of the magnetic coupling through a concerted oxygen-to-metal charge transfer and electronic redistribution within the OH bond of the OH···O magnetic linker. This mechanism accounts for ∼35% of the total experimentally measured singlet-triplet energy difference. This analysis strongly suggests that H bonds might be particularly useful not only in the establishment of intermolecular contacts but also within the basic units of magnetic materials.

6.
J Am Chem Soc ; 130(11): 3566-78, 2008 Mar 19.
Artigo em Inglês | MEDLINE | ID: mdl-18293977

RESUMO

The complexes [Ru(1-C[triple bond]C-1,10-C2B8H9)(dppe)Cp*] (3a), [Ru(1-C[triple bond]C-1,12-C2B10H11)(dppe)Cp*] (3b), [{Ru(dppe)Cp*}2{mu-1,10-(C[triple bond]C)2-1,10-C2B8H8}] (4a) and [{Ru(dppe)Cp*}2{mu-1,12-(C[triple bond]C)2-1,12-C2B10H10}] (4b), which form a representative series of mono- and bimetallic acetylide complexes featuring 10- and 12-vertex carboranes embedded within the diethynyl bridging ligand, have been prepared and structurally characterized. In addition, these compounds have been examined spectroscopically (UV-vis-NIR, IR) in all accessible redox states. The significant separation of the two, one-electron anodic waves observed in the cyclic voltammograms of the bimetallic complexes 4a and 4b is largely independent of the nature of the electrolyte and is attributed to stabilization of the intermediate redox products [4a]+ and [4b]+ through interactions between the metal centers across a distance of ca. 12.5 A. The mono-oxidized bimetallic complexes [4a]+ and [4b]+ exhibit spectroscopic properties consistent with a description of these species in terms of valence-localized (class II) mixed-valence compounds, including a unique low-energy electronic absorption band, attributed to an IVCT-type transition that tails into the IR region. DFT calculations with model systems [4a-H]+ and [4b-H]+ featuring simplified ligand sets reproduce the observed spectroscopic data and localized electronic structures for the mixed-valence cations [4a]+ and [4b]+.


Assuntos
Compostos de Boro/química , Modelos Químicos , Compostos Organometálicos/química , Rutênio/química , Cristalografia por Raios X , Eletroquímica , Elétrons , Ligantes , Modelos Moleculares , Conformação Molecular , Compostos Organometálicos/síntese química , Oxirredução , Espectrofotometria Infravermelho/métodos , Espectrofotometria Ultravioleta/métodos , Espectroscopia de Luz Próxima ao Infravermelho/métodos
7.
Inorg Chem ; 47(2): 572-7, 2008 Jan 21.
Artigo em Inglês | MEDLINE | ID: mdl-18085775

RESUMO

We report the synthesis and structural and magnetic characterization of an original Cu(3) oxidase model. The Schiff base ligand used in the synthesis derives from condensation of acetylacetone with glycine amino acid. The K[Cu(3)(L)(3)(micro(3)-OH)].(H(2)O)(2) complex crystallizes at room temperature in the tetragonal P43212 space group with a = 20.540(3) A and c = 15.866(6) A and consists of triangular Cu(3) units. The magnetic behavior interpretation suggests the presence of spin frustration, which has been investigated by means of ab initio DDCI calculations. It is shown that the system should be viewed as a "ménage à trois" spin-coupled pattern mediated by a central hydroxo group, lifting the doublet degeneracy by approximately 8 cm-1.


Assuntos
Ferro/química , Magnetismo , Modelos Moleculares , Oxirredutases/síntese química , Cristalografia por Raios X , Oxirredutases/química , Conformação Proteica
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