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

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

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3.3.4 X-ray Crystallography<br />

Crystals suitable for X-ray crystallography for III-3 were obtained by sublimation of<br />

the crude residue isolated after the solvent had been fl<strong>as</strong>h distilled to dryness. There is<br />

only one molecule in the <strong>as</strong>ymmetric unit <strong>as</strong> is shown in Figure 3-3. Atoms of interest<br />

have been labelled in the diagram. The C-O bond distance for the ester carbonyl is<br />

1.189(3) Å (C11-O3), compared to the C-O bond distance for the carbonyl group<br />

attached to the ring system at 1.237(7) Å (C6-O2).<br />

The latter bond distance is<br />

substantially greater, confirming the interpretation of the infrared data indicating the<br />

higher stretching frequency of the ester carbonyl. The analogous C-O bond distance<br />

Bond<br />

Bond Length<br />

(Å)<br />

C1-O1 1.391(6)<br />

C11-O1 1.361(4)<br />

C11-O3 1.189(3)<br />

C6-O2 1.237(7)<br />

Table 3-1. Selected bond<br />

distances for III-3.<br />

.<br />

Figure 3-3. Ortep depiction of III-3. Hydrogens removed for clarity.<br />

50% probability ellipsoids<br />

114

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