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

across the entire temperature regime with a Curie constant of 0.375 cm 3 K mol -1 . The
crystal structure which is isomorphous to the DTDA cobalt complex reveals no close
contacts and so there does not appear to be an obvious pathway for magnetic exchange
between neighbouring complexes. So while the addition of steric bulk is sufficient to
prevent the DTDA from forming dimers, in this case it is also enough to prevent any
communication within the lattice resulting in a near-ideal paramagnet.
The mixed zinc complex II-8 however shows more complex behaviour. At room
temperature the χT product has a value of 1.3 cm 3 K mol -1 which is consistent with the 3
isolated spin ½ centers expected from the two mononuclear and one binuclear species
present. As the temperature is lowered, a decrease in this value indicates the presence of
antiferromagnetic exchange coupling. Looking at the crystal structure it is interesting to
note that the binuclear component of the compound has the molecules oriented such that
they have the same orientation as Molecule 2 of the manganese complexes II-6 and II-9.
However the intermolecular interaction of the sulfur from the radical and the oxygen of
the ancillary hfac ligand do not provide a pathway for magnetic exchange in this case, as
the metal is diamagnetic and so this particular component on its own would potentially
have behaviour analogous to II-7 and be purely paramagnetic. So examining the
mononuclear component for signs of intermolecular communication, we see that indeed
these molecules form chains in the solid state along the [010] direction. As shown in
Figure 2-8b, the two sulfur atoms of the DTDA ring are oriented such that they are fairly
close to the nitrogen atoms of the vacant N,N′ pocket of the neighbouring complex. The
interaction of the sulfur atom with the nitrogen atom of the pyramidal ring would not
have a substantial contribution to the magnetic exchange as the spin density on this
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