Self-assembled Transition Metal Coordination Frameworks of ...

the biomimetic (N, O or S) donors reduces A" and increases g", shifting the f
values [37]. The factor a2 is a covalency parameter, which describes the in-plane
sigma bonding, arises from the dipole-dipole interaction between magnetic moments
associated with the spin motion of the electron and the nucleus and its value decreases
with increasing covalency [39]. The stronger covalency should result in smaller
hyperfine interaction. Since, a2 values obtained lies above 0.5 and below 1.0, which
is expected for 100% ionic character of the bonds and become smaller with increasing
covalent bonding, it is inferred that the complexes have some covalent character in the
ligand environment. The values of a2 indicate that approximately 80% of the spin
population is in the copper d 2 2 orbitals of most of the Cu(II) species concerned.
J‘ -Y
= 1/"my",
.-'*'//
|’I'I'A‘|l|
/
_i_ii_;Z_ _l _ . 1
lul
26] 2&3 EDD 320 310 363 383
Bo [mT]
Fig. 4.22. Experimental (black) and simulated best fit (blue) of the EPR spectrum of
complex 8 in DMF at 77 K.
it
\‘/1
t
I
C0pper(II) complexes
157