Aprahamian Ivan, Wegner Hermann A, Sternfeld Tamar, Rauch Karsten, de Meijere Armin, Sheradsky Tuvia, Scott Lawrence T, Rabinovitz Mordecai
Department of Organic Chemistry, The Hebrew University of Jerusalem, Jerusalem 91904, Israel.
Chem Asian J. 2006 Nov 20;1(5):678-85. doi: 10.1002/asia.200600174.
A series of pyrene-based polycyclic aromatic compounds, indeno[cd]pyrene, diindeno[cd,fg]pyrene, diindeno[cd,jk]pyrene, tris-(tert-butylindeno[cd,fg,jk])pyrene, and tetrakis-(tert-butylindeno[cd,fg,jk,mn])pyrene, were reduced with alkali metals in [D8]tetrahydrofuran, and the resulting anions were studied by NMR spectroscopy. It was found that the diatropic character of the dianions obtained depends on the number of annulated indeno groups. When one such group is present, a paratropic dianion is obtained, which is similar to the dianion of the parent pyrene; the effect, however, is weak. When more indeno groups are annulated, the dianions become diatropic owing to the greater number of five-membered rings that can acquire aromatic character as a result of reduction. The 1H NMR chemical shifts of tetrakis-(tert-butylindeno[cd,fg,jk,mn])pyrene in the neutral state show an interesting dependence on concentration that reflects an association of the molecules in solution by pi stacking. This phenomenon was not observed for the reduced species. The trianion radicals of tris-(tert-butylindeno[cd,fg,jk])pyrene and tetrakis-(tert-butylindeno[cd,fg,jk,mn])pyrene undergo reductive dimerization and form bilayered hexaanions.
一系列芘基多环芳烃，茚并[cd]芘、二茚并[cd,fg]芘、二茚并[cd,jk]芘、三（叔丁基茚并[cd,fg,jk]）芘和四（叔丁基茚并[cd,fg,jk,mn]）芘，在[D8]四氢呋喃中用碱金属还原，并通过核磁共振光谱研究所得阴离子。发现所得二价阴离子的抗磁性质取决于稠合茚基的数量。当存在一个这样的基团时，得到一个顺磁二价阴离子，它与母体芘的二价阴离子相似；然而，这种效应较弱。当稠合更多的茚基时，由于还原后可获得芳香性的五元环数量增加，二价阴离子变为抗磁的。中性状态下四（叔丁基茚并[cd,fg,jk,mn]）芘的1H NMR化学位移表现出对浓度的有趣依赖性，这反映了溶液中分子通过π堆积的缔合。对于还原后的物种未观察到这种现象。三（叔丁基茚并[cd,fg,jk]）芘和四（叔丁基茚并[cd,fg,jk,mn]）芘的三价阴离子自由基发生还原二聚反应并形成双层六价阴离子。
