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

with one another with an energy barrier of 23 kcal/mol. 27
The steric protection afforded
by the presence of the chlorine atoms in the 2 and 6 positions of the phenyl substituents
results in a highly persistent radical with significant thermal stability. 12,28
These
compounds can be handled and even stored in the air for extended periods of time and
can be treated with standard purification techniques such as chromatography or
sublimation. However, some derivatives can decompose if exposed to light or if heated
to temperatures in excess of 300 °C. 29
On their own, these types of radicals do not exhibit remarkable magnetic properties,
however some functionalized derivatives of these compounds have been used as
molecular synthons to build up supramolecular structures with organic and metal-organic
components which do have interesting magnetic behaviour. 30
Also, recent studies have
shown that they can be grafted onto a gold surface which in turn exhibit excellent
electron transport properties. 31
This could potentially provide insight toward the
development of new spintronic materials.
1.2.2 α-Nitronyl-Nitroxides
Another important class of radicals geared toward the development of moleculebased
materials is nitroxides, including α-nitronyl-nitroxides (I-2). These have found
several applications, including spin-probes, 32,33
paramagnetic relaxation enhancement
dopants for protein-peptide binding 34 and as a tool to measure circulating blood volume. 35
This radical’s stability is bolstered by the presence of the methyl groups on the saturated
carbon-backbone to sterically inhibit potentially reactive contaminants such as air or
water from accessing the radical-bearing atoms, but also as mentioned above, the
13