Exchange coupled high spin Co(II) and Ni(II) complexes with high magnetic moment

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Dinuclear metallohydrolases containing distorted octahedral Co(II) or Ni(II) ions in there active site are an important class of metalloenzymes. Because of this there is a high demand of the chararterization of such systems and of adequate model system. The descrption of the magnetic behaviour of two interacting high spin Co(II) ions in octahedral surrounding is among the most interesting and complicated cases of molecular magnetism, because the 4T1g ground state is orbitally degenerate leading to the need of including as well spin and orbital contributions. Within this project some Co(II) and Ni(II) dimers mainly from the series of model hydrolases will be magnetically and with help of UV/VIS and Magnetic Circular Dichroism (MCD) Spectroscopy investigated. In our previous work we could show some of complexes are with an unusual high magnetic moment being therefore of considerable interest. Some synthetic work has to be done to obtain the samples. Existing models for the interpretaion of the magnetic properties of Co(II) will be tested, e.g one can try to neglect the orbitally dependent term of the exchange interaction after Lines and include the orbital momentum of the 4T1g term and the spin orbit coupling within this term. Moreover, the role of the low lying excited term will be investigated The treatment of the magnetic properties of Ni(II) dimers must include as a minimum the Zero Field Splitting. Results of MCD Spectroscopy will be used as an independent source for characterizing the magnetic properties.