RESUMEN
The magnetic interaction in the Ni(ii)-Fe(iii) Prussian Blue Analogue is investigated by means of Difference Dedicated Configuration Interaction (DDCI) calculations. Embedded cluster calculations are performed to extract the exchange coupling constant J with respect to an opening of the Ni-NC-Fe bridge while maintaining a rigid Fe(CN)6 unit. It is shown that such active distortion significantly modifies the magnetic interaction scheme in the material. Not only a ferromagnetic to antiferromagnetic transition is observed, but the J value is varied from +11.4 cm(-1) to -12.5 cm(-1) when the Ni-Fe cyanide bridge is opened by 20°. The enhancement of the intersite hopping electron transfer integral by a factor of 1.5 can be correlated with the observed Na(+)-ion mobility in a unified "cation-coupled electron transfer" (CCET) process. These results stress the complexity and originality of this class of compounds evidenced by the versatility of their magnetic network.
RESUMEN
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 â¼35% 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.
RESUMEN
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.