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

2.3 Magnetic Measurments
2.3.1 pymDSDA II-1
The magnetic susceptibility was measured for the radical pymDSDA, showing that it
is diamagnetic. This is consistent with the dimerization observed from the X-ray
crystallography examined previously (Figure 2-4). The χT product is negative at room
temperature and the value does not change substantially as the temperature is lowered
from 300 K down to 1.8 K.
2.3.2 [Ni(hfac) 2 ] 2·pymDSDA II-5
The NiDTDA complex [Ni(hfac) 2 ] 2·pymDTDA II-11, while reported in a previous
publication 2 will be reviewed here briefly to compare it to II-5. The magnetic
susceptibility for II-11 at 1000 Oe, seen in Figure 3-7 shows a steady increase in the χT
product from 3.1 cm 3 K mol -1 at room temperature to 4.2 cm 3 K mol -1 at 25 K which is
very close to the value of 4.377 cm 3 K mol -1 that is expected from the approximation
from equation 1.8, indicating dominant ferromagnetic (FM) interactions between the two
nickel(II) nuclei and the radical. The observed coupling results in an overall ground state
spin of S T = 5/2. This can be seen in Scheme 2-4 a. This is followed by a decrease in the
χT product as the temperature is further lowered to 1.8 K and is likely a result of weak
antiferromagnetic coupling between neighbouring complexes or as a result of
magnetoanisotropy arising from the nickel ions (Figure 2-10).
Compound II-5, by
contrast, since it is dimerized, has much different behaviour. As the dimerization arises
due to Se...Se contacts between two radical ligands, they can in this case be considered to
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