Dynamic Molecular Tweezers Composed of Dibenzocyclooctatetraene Units: Synthesis, Properties, and Thermochromism in Host-Guest Complexes
作者:Tomohiko Nishiuchi、Yoshiyuki Kuwatani、Tohru Nishinaga、Masahiko Iyoda
DOI:10.1002/chem.200900623
日期:2009.7.13
Novel dynamic molecular tweezers (DMTs) 3 a, 3 b, 4 a, 4 b, and 5 b, composed of two tub‐shaped dibenzocyclooctatetraene (DBCOT) units, were designed and synthesized. The cyclooctatetraene (COT) rings of these DMTs readily invert in solution, and the molecular structure shows rigid syn and anti forms in an equilibrium mixture in solution. The syn and anti conformers can be observed by NMR. The isomerization
新颖动态分子镊子(DMTS)3,图3b,图4a,图4b和图5b中,两个桶形dibenzocyclooctatetraene组成(DBCOT)单元,设计并合成。这些DMT的环辛酸酯(COT)环易于在溶液中转化,并且分子结构在溶液中的平衡混合物中显示出刚性的顺式和反式形式。的顺式和反构象异构体可通过NMR观察到。3a,3b,4a,4b和5b的异构化势垒取决于COT环的取代基和中心苯环的质子之间的空间排斥力,其范围在16.5–21.3 kcal mol -1之间。这些DMT与溶液,固态的2,3-二氯-5,6-二氰基-1,4-苯醌(DDQ)和1,2,4,5-四氰基苯(TCNB)形成复合物。这些DMT的结合能力随COT上的供电子取代基而增加,这增加了syn形式空穴的电子密度,这在理论计算中得到了支持。另外,发现DMT的末端烷氧基链的延长引起范德华斯与客体分子接触的增强。因此,5 b,具有CH 2CO