The Synthesis and Characterization of Stable Radicals Containing the Thiazyl (SN) Fragment and Their Use as Building Blocks for Advanced Functional Materials - Stable Radicals: Fundamentals and Applied Aspects of Odd-Electron Compounds - page 364

I 2(g)

(a) (b) (c)

Figure 9.25 (a) Structure of β -HCN 2 S 2 viewed down the π stacks. (b) Stacking of π dimers of β -HCN 2 S 2 .c)

Structureofstacksin(HCN 2 S 2 ) 6 I 1 . 1 . 105

the diradical/iodide salts, suggesting a much smaller degree of charge transfer from the radical - which
nonetheless still leads to high conductivity (15 S/cm at room temperature).

9.4.3 Magnetic properties of thiazyl radicals

The magnetic properties of stable radical-based materials have been enthusiastically explored for
over two decades. 232 The goals of these pursuits work span fundamental science (the development
of structure - magnetism relationships in radical-based compounds and materials) and more practical
challenges (the creation of molecule-based magnetically ordered materials). The use of molecular
or organic components in the design and construction of new magnetic materials - whether in
radical-based molecular crystals, 233,234 incorporated into polymers, 235 or combined with metals as
radical ligands 236 - offers a number of possible advantages including solubility, processibility, and
multifunctionality. 237 Early efforts in this field were dominated by nitroxide radicals 234,238 owingtotheir
excellent stability; triarylmethyl radicals 239 and verdazyl radicals 240 have also played significant roles.
Thiazyl radicals are relatively new additions to the chemists' toolkit of paramagnetic building blocks,
largely because the synthesis and characterization of most thiazyl radicals was not fully developed until
the 1980s and 1990s. However, interest in the magnetic properties of thiazyl radicals has steadily grown to
the point where these radicals are now among the most important ones in molecular magnetism. Rawson
reviewed the magnetic properties of thiazyls and outlined many of the general challenges of the field of
designing molecule-based magnets. 212,215 In the past decade in particular, a very large number what could
be called “case studies” - that is, papers which report the structural and magnetic characterization of a small
number of closely related thiazyl radicals - have been published. Rather than provide a comprehensive
account of this body of work, this section aims to distill some of the general magnetic trends and the more
important developments in thiazyl radical magnetochemistry.

9.4.3.1 Magnetic properties of thiazyl radical-based π dimers and π stacks

In addition to playing a central role in charge transport properties (Sections 9.4.1 and 9.4.2), thiazyl radical
π π

dimers and stacks also lead to a rich array of magnetic properties. A generic orbital interaction diagram