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Issue 3, 1993
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Verdazyls. Part 33. EPR and ENDOR studies of 6-oxo- and 6-thioxoverdazyls. X-Ray molecular structure of 1,3,5-triphenyl-6-oxoverdazyl and 3-tert-butyl-1,5-diphenyl-6-thioxoverdazyl

Abstract

A range of 6-oxoverdazyls 2bh and 6-thioxoverdazyls 3ac and 3eh has been directly prepared by dehydrogenation of the corresponding 1, 4, 5, 6-tetrahydro-1, 2, 4, 5-tetrazin-3(2H)-ones 5bh and thiones 7ac and 7ehwith lead dioxide, potassium hexacyanoferrate (III), or bis(4-methylphenyl)-aminyl. X-Ray analyses reveal a nearly planar verdazyl framework for the oxoverdazyl 2a, whereas the thioxoverdazyl 3ftakes on a flat boat conformation. In the latter, owing to the bulky sulfur the N-phenyl groups are considerably twisted out of the plane of the verdazyl ring. Electronic absorption spectra of the deeply coloured radicals exhibit characteristic bands in the visible region with λmax, 1 ranging from 445 to 608 nm. EPR, ENDOR and 2H NMR studies have led to a complete analysis and full assignment of all hyperfine coupling constants. The π-SOMO of 6-oxo-2 and 6-thioxo-verdazyls 3, having nodes at C(3) and C(6), is mainly confined to the nitrogens of the verdazyl ring. Spin delocalization into the N-phenyl groups is reduced, particularly in the 6-thioxoverdazyls, owing to the large torsion angle about the N–C(phenyl) bond.

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J. Chem. Soc., Perkin Trans. 2, 1993, 535-544
Article type
Paper

Verdazyls. Part 33. EPR and ENDOR studies of 6-oxo- and 6-thioxoverdazyls. X-Ray molecular structure of 1,3,5-triphenyl-6-oxoverdazyl and 3-tert-butyl-1,5-diphenyl-6-thioxoverdazyl

F. A. Neugebauer, H. Fischer and C. Krieger, J. Chem. Soc., Perkin Trans. 2, 1993, 535
DOI: 10.1039/P29930000535

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