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

good spectroscopic handle for this species as it possesses very characteristic stretching
frequencies. The asymmetric stretch appears as a strong absorption at 1513 cm -1 and the
symmetric stretch is at 1354 cm -1 . The peaks at 533 and 764 cm -1 also arise due to the inplane
deformation of the NO 2 group. 9 A large majority of the other peaks are related to
the C-C stretches and bends or C-H bending vibrations and do not change substantially
across the series of compounds in this section and are therefore of less concern than those
discussed already.
Figure 5-11 shows the infrared transmission spectrum of V-12 from approximately
2000 to 400 cm -1 . Not shown in this spectrum are the strong intensity peaks in the 3350-
3100 cm -1 range corresponding to the N-H stretching vibrations. There is also a band at
2575 cm -1 of a medium intensity, related to these modes (the full spectrum can be seen in
the appendix). The quinone carbonyl stretch has shifted substantially to 1736 cm -1
suggesting that a greater amount of electron density has been donated into the antibonding
C-O orbital. The disappearance of the other peaks associated with the nitro
group is also evidence for a successful transformation. The high intensity peaks at 1643
and 1509 cm -1 are related to symmetric and asymmetric deformation vibrations, although
there are also aromatic C=C stretching vibrations in this region and so definitive
assignment is difficult. The low intensity bands around 1925 and 1951 cm -1 are believed
to be a combination band involving NH + 3 deformation vibrations. There are several
sharp peaks from 1260 to 1190 cm -1 , two of which are characteristic for primary amine
hydrohalides arising from the rocking vibration of the NH + 3 group. The C-N stretching
vibrations show up at 1361 cm -1 and one of the peaks between the 1260 and 1190 cm -1
158