EPR of two Cu2+ complexes showing dynamic Jahn-Teller effects |
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| Authors: | M A Hitchman C J Simmons H Stratemeier |
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| Institution: | (1) Chemistry Department, Faculty of Science (Demiatta), Mansoura University, Demiatta, Egypt;(2) Chemistry Department, Faculty of Science, King Khalid University, Abha, Saudi Arabia |
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| Abstract: | The powder electron paramagnetic resonance spectra of ∼1% Cu doped into Zn(bipy)2(NO2)]NO3 and Zn(bipyam)2(NO2)]NO3, bipy = 2,2′-bipyridyl, bipyam = 2,2′-bipyridylamine, over the temperature range 4.2–300 K are reported. For Zn/Cu(bipy)2(NO2)]NO3 a spectrum characteristic of a tetragonally elongated octahedral complex with a slight orthorhombic distortion is observed below ∼50 K, but above this temperature the signals associated with the two higherg-values gradually converge. At low temperature a spectrum similar to that of the bipy complex is observed for Zn/Cu(bipyam)2(NO2)]NO3, but between 40 and 60 K the spectrum gradually changes to one characteristic of a tetragonalg-tensor with g∥ < g⊥. The spectra may be interpreted satisfactorily with a model in which the temperature dependence of theg-vainlues is estimated from the vibronic wavefunctions of a copper(II) complex under the influence of second-order Jahn-Teller coupling and a ligand field of tetragonal symmetry perturbed by crystal lattice forces. The results are consistent with the crystal structures reported for the compounds at various temperatures. |
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