High-field Mossbauer spectroscopy on dinuclear iron(II) spin crossover complexes

The dinuclear complex [{Fe(L-N4Me2)}(2)(BzImCOO)](ClO4)(2)*0.5(CH3)(2)CO has been investigated by Mossbauer spectroscopy carried out in the temperature range from T = 5 K up to T = 190 K with externally applied magnetic fields of up to B = 5 T. By means of a consistent simulation of all experimental data sets within the Spin Hamiltonian formalism, the zero-field splitting and the rhombicity parameter of the ferrous high-spin site could be determined to be D = 7.2 +/- 0.5 cm (-aEuro parts per thousand 1) and E/D = 0.1 +/- 0.02. The sign of the quadrupole splitting is positive which indicates that the ferrous high-spin site of the dinuclear complex [{Fe(L-N4Me2)}(2)(BzImCOO)]-(ClO4)(2)*0.5(CH3)(2)CO has an electronic ground state with the d (xy) orbital twofold occupied.