1,2,3-Dithiazolyl and 1,2,35-Dithiadiazolyl Radicals as Spin-Bearing ...

The χT product for II-6 at room temperature is 8.1 cm 3
K mol -1 . As the
temperature is lowered, the χT product increases to 12.5 cm 3 K mol -1 at 14 K, which is
consistent with a ground state S = 9/2, suggesting antiferromagnetic coupling between the
two manganese ions and the bridging central radical. As the temperature is lowered
further, the χT product continues to increase sharply to 13.9 cm 3 K mol -1 at 1.8 K. The
primary difference between the two sets of data is that the magnetic susceptibility of II-9
does not plateau before the sharp asymptotic increase of the χT product down to 1.8 K.
There are two potential explanations for this. It is possible that the intermolecular
contacts in II-6 are not as strong as those seen in II-9, or it may be that head-to-head
interactions are more favourable for the selenium analogue resulting in a shorter average
chain length. This will be explored in more detail in section 2.4.
Scheme 2-4. Proposed coupling
scheme for II-6 and II-9.
Figure 2-11. Magnetic susceptibility (χT) for II-9 and II-6 as a function
of temperature from 300 to 2 K at 1000 Oe.
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