Rhombic field

Stretching mode 0 g. The original idea was that static JT distortions could produce the large observed anisotropy however, a simple static treatment showed comparable energies of the zero-point vibration (fiw = 350 cm or 225 cm" ), the JT stabilization (Ejt = 516 cm" ), the spin-orbit interaction = 435 cm" ) and the rhombic field due to the azide ion (Hrj, = 60 cm" ). Therefore all interactions had to be considered simultaneously including dynamic effects. The used Hamiltonian was... 

The EPR of the iron complex exhibits the characteristic g = 4.3 signal of high spin ferric ion in rhombic fields (63). It should be noted that since binding of a 3+ cation releases two protons per catechol ligand, the chelate is a 3— anion, i.e. there is an excess of one electronic charge on each benzenoid ring. 

It is seen that the tetragonal field does not contribute to rj while the rhombic field does not contribute to q. 

Fig. 6. Splitting of D and F terms in ligand fields of cubic (octahedral and tetrahedral) symmetry with a small superimposed rhombic field component.

In an octahedral field, the ground state is T2. An axial field and spin-orbit coupling leave a singlet (m=0) and a doublet (m= 1) lowest. A rhombic field splits the doublet. In most cases, low temperature is required to observe the spectrum, since at high temperatures, rapid spin-lattice relaxation broadens the lines. Fep2 has been examined in detail using the spin Hamiltonian... 

In an octahedral field, the ground state is Idj. Spin-orbit coupling does not remove the spin degeneracy (/ ). The lowest level is split into a singlet and a doublet by axial fields, into three singlets by a rhombic field. The values listed are interpreted in terms of the following spin Hamiltonian with 5 = 1 ... 

In an octahedral field, the ground state is which is split by a tetragonal or rhombic field into two Kramers doublets. Paramagnetic resonance is observed for the lower doublet. 

Blumbcrg. W.E. Magn. Resonance Biol. Syst., Proc. Int. Conf.. 2nd, Stockholm 1966,119 (Pub. 1967). The ERR of high-spin ferric ion in rhombic fields. 

---