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

ise to the observed antiferromagnetic coupling. The iron complex similarly is a high
spin d 6 with only one t 2g orbital fully occupied making it straightforward to attribute the
observed coupling to the interaction of the π* SOMO and an orbital from the metal ion
which would give rise to non-orthogonal overlap and paired spins.
One advantage to coordinating these radicals is that the steric bulk afforded by the
ancillary ligands on the metal ion helps to protect the sulfur atoms of neighbouring
complexes from interacting with one another to form closed-shell diamagnetic species,
which was one of the primary concerns for using DTDA radicals as building blocks for
magnetic materials. This dimerization is, in fact suppressed in I-27b, I-27c and I-27d,
however I-27a and I-27e complexes do form dimers, although this has been attributed to
their deviation from rigid octahedral site symmetry. From the X-ray structure of I-27e it
can be shown that there is an elongation of one of its axes, typical for six coordinate d 9
complexes and I-27a has a geometry that can more accurately be described as trigonal
prismatic.
Following this success, several new DTDA based radicals were designed by slight
modification of the pyridyl group to afford the 4- (I-28) and 3-cyano-6-pyridyl (I-29)
DTDAs as well as the 4-bromo-6-pyridyl DTDA (I-30). These groups were chosen due to
the fact that cyano functional groups have been shown to have an interesting impact on
the packing for, most famously, I-16f. 81 And the presence of an electronegative bromine
substituent has also been shown to give rise to analogous contacts with the electropositive
sulfur atoms of the DTDA ring 150
which promote lateral contacts and suppress
dimerization.
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