Berlin 2008 – wissenschaftliches Programm

Bereiche | Tage | Auswahl | Suche | Downloads | Hilfe

MA: Fachverband Magnetismus

MA 27: Bio- and Molecular Magnetism

MA 27.9: Vortrag

Donnerstag, 28. Februar 2008, 16:30–16:45, EB 202

Coordination geometry induced changes on magnetic parameters of Cu(II) complexes — •Björn Bräuer¹, Tobias Rüffer¹, Dante Gatteschi², Maria Fittipaldi², Andrea Caneschi², Florian Weigend³, and Georgeta Salvan¹ — ¹Chemnitz University of Technology, Department of Physics, Reichenhainer Straße 70, D-09126 Chemnitz — ²University of Florence, Department of Chemistry, Via della Lastruccia 3, I-50019 Florence — ³Forschungszentrum Karlsruhe, Institute for Nanotechnology, Postfach 3640, D-76021 Karlsruhe

Cu(II)-bis(oxamato) complexes are prominent representatives for basic research studies of magnetic exchange phenomena [1]. We have used Electron Paramagnetic Resonance (EPR) spectroscopy to study the dependence of the hyperfine coupling constants A and the spin density distribution on the structural parameters of mono-nuclear complexes. Furthermore, the influence of such variations on the super exchange coupling parameter J of the respective tri-nuclear complexes was investigated. It was shown that deviations from the square planar coordination geometry decrease the delocalisation of spins leading to a smaller J value, i. e. a smaller antiferromagnetic interaction. The obtained parameters were also calculated by means of Density Functional Theory (DFT). The J parameters were determined using the broken symmetry approach and the influence of packing effects, counter ions, and bridging ligands were investigated. The COnductor like Screening Field MOdel (COSMO) was found to be a suitable model for reliable predictions of experimental trends. [1] O. Kahn, Molecular Magnetism, VCH Weinheim, 1993.