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

However, as the temperature is lowered further the χT product increases to
13.9 cm 3 K mol -1 at 1.8 K with a steep slope.
As stated previously, this behaviour is very similar to that reported for the sulfur
containing analogue, II-9. At the time that II-9 was reported, the origin of the sharp
increase in χT at low T was unknown, but a coordination complex of 4-(2′-benzoxazolyl)-
1,2,3,5-DTDA with Mn 2+ and two ancillary hfac ligands (II-12) 18 revealed an important
feature that these complexes can potentially possess which gives rise to this type of
result. Compound II-12 exhibits antiferromagnetic coupling between the metal
center (S = 5/2) and the radical to give an overall S = 2 for the complex. This can be seen
in the χT vs T data by a decrease in the χT product as the temperature is lowered from
300 K down to 50 K. However, below this temperature the susceptibility increases
sharply to a value consistent with a ground state spin of twice the expected value for a
II-12
Figure 2-13. Intermolecular contacts in II-12 which give rise
to sigmoidal χT vs logT data.
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