Regensburg 2002 – wissenschaftliches Programm
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CPP: Chemische Physik und Polymerphysik
CPP 2: Neue Methoden I
CPP 2.2: Vortrag
Montag, 11. März 2002, 11:20–11:40, H39
Coordination states of cooper in Cu(terpy)2(PF6)2 systems analysed by ESR — •A. Mirea1, W. Bietsch1, M.N. Grecu2, and M. Schwoerer1 — 1Lehrstuhl für Experimentalphysik II, Universität Bayreuth, 95440 Bayreuth, Germany — 2National Institute for Materials Physics, R - 76900 Bucharest, Romania
X- and Q-band ESR measurements on both single crystals and polycrystalline samples of Cu(terpy)2(PF6)2 non-substituted and CH3-substituted 2,2’:6’,2" - terpyridine ligands (terpy) have been made over the temperature range 10-500 K. Depending on the substituent of terpyridine ligand a change in the ground state of the Cu(II) complex is found. At 300 K, in contrast to the non-substituted complex, for which an "inverse" axial g-tensor was found with g⊥>g∥>2.00 (dz2), the CH3-substituted complex exhibits an orthorhombic g-tensor (dx2−y2). Bonding parameters have been derived from the hyperfine (AxCu = 118 G, AyCu = 30 G, AzCu = 76.8 G) and superhyperfine structures (AzN = 16 G, AzH = 7.6 G) in the ESR spectra, which are well resolved in diluted single crystals at 20 K. The temperature dependence of the principal g-values evaluated from the simulated ESR spectra of polycrystalline samples are interpreted by taking into account the Jahn-Teller effect. The differences in energies of the Jahn-Teller configurations of the Cu(II) complex have been estimated. We note that the static Jahn-Teller effect observed in different dilutions of polycrystalline samples for CH3-substituted complex, is completly stabilized by thermal treatement above 450 K.