The development in the field of coordination polymers or metal-organic coordination networks, MOCNs (metal-organic frameworks, MOFs) is assessed in terms of property investigations in the areas of catalysis, chirality, conductivity, luminescence, magnetism, spin-transition (spin-crossover), non-linear optics (NLO) and porosity or zeolitic behavior upon which potential applications could be based.

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Engineering coordination polymers towards applications

Magnetism of lanthanides in molecular materials with transition-metal ions and organic radicals.

The coordination chemistry of pyrazole-derived ligands

When two paramagnetic transition metal ions are present in the same molecular entity, the magnetic properties can be totally different from the sum of the magnetic properties of each ion surrounded by its nearest neighbors. These new properties depend on the nature and the magnitude of the interaction between the metal ions through the bridging ligands. If both ions have an unpaired electron (e.g. Cu2+ ions), then the molecular state of lowest energy is either a spin singlet or a spin triplet. In the former case, the interaction is said to be antiferromagnetic, in the latter case ferromagnetic. The nature and the order of magnitude of the interaction can be engineered by judiciously choosing the interacting metal ions and the bridging and terminal ligands, and, thus, by the symmetry and the delocalization of the orbitals centered on the metal ions and occupied by the unpaired electrons (magnetic orbitals). The first success in this “molecular engineering” of bimetallic compounds was in the synthesis of a Cu2+VO2+ heterobimetallic complex in which the interaction is purely ferro-magnetic. The same strategy could be utilized for designing molecular ferromagnets, one of the major challenges in the area of molecular materials. Another striking result is the possibility of tuning the magnitude of the interaction through a given bridging network by modifying the nature of the terminal ligands, which, in some way, play the role of “adjusting screws”. By careful selection of the bridging and terminal ligands, a very large antiferro-magnetic interaction can be achieved, even if the metal ions are far away from each other. Some sulfur-containing bridges are especially suitable in this respect.

Dinuclear Complexes with Predictable Magnetic Properties

Constructing magnetic molecular solids by employing three-atom ligands as bridges

Crystal and molecular structure of and magnetic coupling in two complexes containing gadolinium(III) and copper(II) ions

Crystal and molecular structure and magnetic properties of a trinuclear complex containing exchange-coupled GdCu2 species

Angular overlap interpretation of the magnetic properties of copper(II) dimers

Magnetic exchange interactions have been calculated in the framework of the density functional (DF) theory for the quite rare exchange coupled binuclear compounds in which the magnetic centers belong to the 4d series:  [{MoV(O)(Tp*)Cl}2(μ-X)], (where X is one of the dihydroxybenzene bridging ligands [1,4-OC6H4O]2- or [1,3-OC6H4O]2- and Tp* is tris(3,5-dimethylpyrazolyl)hydroborate. The exchange coupling constant J has been nicely reproduced with the use of the broken symmetry (BS) approach to avoid the multideterminant structure of the singlet state. Several local and gradient-corrected functionals have been tested. In order to determine relevant magneto-structural correlations between structural parameters and exchange coupling constants, we also performed calculations on model systems in which the relative orientations of the two molybdenum moieties with respect to the aromatic ring were varied. These calculations showed that the actual value of the magnetic coupling constant J is influenced not only by...

A. Bencini

Papers

Crystal and molecular structure of and magnetic coupling in two complexes containing gadolinium(III) and copper(II) ions

Crystal and molecular structure and magnetic properties of a trinuclear complex containing exchange-coupled GdCu2 species

Angular overlap interpretation of the magnetic properties of copper(II) dimers

Density functional modeling of long range magnetic interactions in binuclear oxomolybdenum(v) complexes

The angular overlap model for the description of the paramagnetic properties of transition metal complexes