VERDAZYLS .33. EPR AND ENDOR STUDIES OF 6-OXOVERDAZYLS AND 6-THIOXOVERDAZYLS - X-RAY MOLECULAR-STRUCTURE OF 1,3,5-TRIPHENYL-6-OXOVERDAZYL AND 3-TERT-BUTYL-1,5-DIPHENYL-6-THIOXOVERDAZYL
VERDAZYLS .33. EPR AND ENDOR STUDIES OF 6-OXOVERDAZYLS AND 6-THIOXOVERDAZYLS - X-RAY MOLECULAR-STRUCTURE OF 1,3,5-TRIPHENYL-6-OXOVERDAZYL AND 3-TERT-BUTYL-1,5-DIPHENYL-6-THIOXOVERDAZYL
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DOI：
10.1039/p29930000535
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发表时间：
1993-03-01
期刊：
影响因子：
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通讯作者：
KRIEGER, C
中科院分区：
文献类型：
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作者：
NEUGEBAUER, FA;FISCHER, H;KRIEGER, C
用二氧化铅、六氰合铁（iii）酸钾或双（4-甲基苯基）-氨基使相应的1，4，5，6-四氢-1，2，4，5-四嗪-3（2 H）-酮5 b-h和硫酮7a-c和7 e-h脱氢，直接制备了一系列6-氧代苯并咪唑2b-h和6-硫代苯并咪唑3a-c和3e-h。X-射线分析揭示了oxoverdazyl 2a的一个几乎平面的verdazyl框架，而thioxoverdazyl 3f呈现出一个平底船构象。在后者中，由于庞大的硫，N-苯基基团被显著地扭曲出Verdazyl环的平面。深色自由基的电子吸收光谱在可见光区具有λ（max，1）范围为445 - 608 nm的特征谱带。EPR，ENDOR和H-2 NMR的研究导致了一个完整的分析和所有的超精细耦合常数的充分分配。在C（3）和C（6）上具有节点的6-氧代-2和6-硫代咪唑基3的pi-SOMO主要限于咪唑环的氮。自旋离域到N-苯基基团减少，特别是在6-thioxoverdazyls，由于大的扭转角的N-C（苯基）键。
A range of 6-oxoverdazyls 2b-h and 6-thioxoverdazyls 3a-c and 3e-h has been directly prepared by dehydrogenation of the corresponding 1,4,5,6-tetrahydro-1,2,4,5-tetrazin-3(2H)-ones 5b-h and thiones 7a-c and 7e-h with 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 3f takes 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 lambda(max,1) ranging from 445 to 608 nm. EPR, ENDOR and H-2 NMR studies have led to a complete analysis and full assignment of all hyperfine coupling constants. The pi-SOMO of 6-oxo- 2 and 6-thioxoverdazyls 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.