Why the pyrochlore-like antiferromagnet NaCu3F7is magnetically non-frustrated.

We present a theoretical study of the magnetic properties for the pyrochlore-like NaCu3F7compound, which surprisingly experience little or no frustration. The magnetic effective exchange interactions were calculated usingab-initiomethods explicitly treating the electronic correlation. A model Hamiltonian (quantum Heisenberg Hamiltonian, and for comparison a spin 1/2 Ising Hamiltonian) was built from these interactions and used to determine the zero temperature magnetic order versus magnetic field. The magnetic order at zero magnetic field is non frustrated and associated with the propagation vectorq→=(0,0,0). The magnetization versus magnetic field reveals the existence of a 1/3 plateau that could be observed in high-pulsed magnetic field experiments. Analyzing the magnetic interactions, we highlight the importance of the magnetic ion nature, and the lattice distortion, in the non-frustrated nature of the NaCu3F7magnetic structure, despite its triangular/Kagome subnetworks. We believe that this non-frustrated behavior could also take place in other triangular copper-based systems.

Synthesis, characterization, electrochemical and photophysical properties of elbow-shaped trinuclear Ru(II) complexes, building blocks for novel supramolecular constructions.

Three trinuclear elbow-shaped Ru(II) complexes based on the non symmetrical bridging PHEHAT ligand (PHEHAT = 1,10-phenanthrolino[5,6-b]-1,4,5,8,9,12-hexaazatriphenylene) have been prepared and characterized by NMR, electrochemistry, absorption and emission spectroscopy. It is shown that the dichloro trinuclear complex 1 should behave as an excellent precursor for the synthesis of larger species. Indeed, it reacts easily with 1,10-phenanthroline (phen) and 1,4,5,8-tetraazaphenanthrene (TAP) and leads to the trinuclear compounds 2 and 3, respectively. The electrochemical and emission studies indicate that for 2 and 3, there is an intramolecular energy transfer from the center to the periphery of the elbow-shaped trinuclear complex, whereas for complex 1 the energy transfer takes place in the other direction.

Dendritic tetranuclear Ru(II) complexes based on the nonsymmetrical PHEHAT bridging ligand and their building blocks: synthesis, characterization, and electrochemical and photophysical properties.

Dinuclear and tetranuclear Ru(II) compounds 1, 2, 3, and 4 based on the PHEHAT ligand (PHEHAT = 1,10-phenanthrolino[5,6-b]-1,4,5,8,9,12-hexaazatriphenylene) are prepared and characterized on the basis of the data for other related mononuclear species. Their electrochemical and spectroscopic behaviors are discussed. The nonspectroelectrochemical correlation obtained for 1, 2, 3, and 4 is explained on the basis of these data. From the behavior in emission, it is concluded that the internal energy transfer takes place from the core to the peripheral metallic units in 3 and 4.

A mixed-bridging ligand nonanuclear Ru(II) dendrimer containing a tris- chelating core. Synthesis and redox properties.

The first ligand-cored dendrimer based on branching Ru(II) centers and containing mixed polypyridine bridging ligands has been prepared; redox experiments suggest that the redox-active core is not reduced at the expected potential, probably as a consequence of shielding induced by the rigid dendritic array.