作者:Christopher Kauffmann、Walter M. Müller、Fritz Vögtle、Sarah Weinman、Sarah Abramson、Benzion Fuchs
DOI:10.1055/s-1999-3466
日期:1999.5
Two new chiral and photoisomerizable rotaxanes (9m, 9p) have been prepared, bearing the longest non-polymeric axle known so far: the axles (6m, 6p) are polyether chains made of alternating triethyleneglycol/hydroquinone units, bearing a central meta- or para-azobenzoyl moiety and terminal tetraacetylglucoside stopper groups, while the wheel is the cyclobis(p-xylylene)bis(4,4′-bipyridinium) salt. Temperature dependent 1H NMR measurements reveal that the translational process of the wheel across the azobenzene unit in the E-configuration is favoured for the para-rotaxane 9p compared to the meta isomer 9m. The azobenzene core of the free axles (6m, 6p) and rotaxanes (9m, 9p) undergo photochemical E/Z-isomerisation: from (E) to (Z) by irradiation at low wavelength and back from (Z) to (E) at high wavelength. Complete (Z) to (E) conversion was achieved by thermal isomerization.
我们制备出了两种新的手性和光异构的轮烷(9m、9p),它们具有迄今已知的最长的非聚合轴:轴(6m、6p)是由三乙二醇/对苯二酚单元交替组成的聚醚链,中间带有一个元或对偶氮苯甲酰基和末端的四乙酰葡萄糖苷阻断基团,而轮则是环双(对羟基乙烯)双(4,4′-联吡啶)盐。与温度相关的 1H NMR 测量结果表明,与元异构体 9m 相比,对位己二烷 9p 在 E 构型中穿过偶氮苯单元的转轮平移过程更有利。自由轴(6m,6p)和对位己二烷(9m,9p)的偶氮苯核心会发生光化学 E/Z 异构化:在低波长照射下从 (E) 变为 (Z),在高波长照射下又从 (Z) 变回 (E)。通过热异构化实现了从 (Z) 到 (E) 的完全转化。