Self-assembled Transition Metal Coordination Frameworks of ...

Chapter 3
antiferromagnetic coupling. For complex 4 (the temperature dependence curves of X,“
and um are shown in Fig. 3.32), however, we could not get a reasonable fit, may be
associated with zero-field splitting (D) especially at lower temperatures and/or due to
slight variations in M—X—M angles, so that more J values need to be considered. The
M—O—M arrangement at 180° is known as an ideal structure for strong
antiferromagnetism [55]. This linearity as the origin of strong AF coupling is in
accordance with VB [56-58] and MO [59] studies. Logically, Kahn also explained this
feature in his book [60]. The temperature dependence of effective magnetic moment
curves for complexes 1 and 4 are also consistent with these results, though lacks
reasonable fits. We have reported these results recently [61]. The field dependence of
magnetic susceptibility
6
for these compounds (Fig. 3. 33) not showed any indication of
ferromagnetic
__
component and is in agreement
/(.1
with overall antiferromagnetism.
8-.
I
;
MiZ 9- '
=: 4 2 - -I‘.-,3‘ ""
I
. * 55' ‘I . _. 1' I"'
g -__||I ‘nu
.10‘
0-.
' I ' I ' I ' I ' I ' I ' I ' I ‘
O 50 100 150 200 250 300 350
T (K)
Fig. 3.29. Temperature dependence of effective magnetic moment um (I) for the
complex 1 (the variations are due to poor data collection).
116