Transannular pi-pi Interaction of (4n)pi Systems

我们感兴趣的是研究两个π系统在非常接近的情况下相互重叠时如何相互作用。根据前线分子轨道计算，Greenberg等人预言了（4 n +2）pi-（4 n +2）pi体系中的π-π相互作用是不稳定的，（4 n +2）pi-（4 n）pi体系中的π-π相互作用是稳定的，（4 n）pi-（4 n）pi体系中的π-π相互作用比（4 n +2）pi-（4 n）pi体系中的π-π相互作用稳定。为了实验验证这一有趣的预测，我们认为[3.3]环芳烷是最合适的模型，因为[3.3]环芳烷可以精确地计算π-π相互作用，而不受应变效应的干扰.作为研究（4 n +2）（4 n +2）相互作用（n*2）的模型化合物，我们合成了[3.3]环芳烷，其中含有Vogel的1，6-亚甲基[10]轮烯，它们是含有两个轮烯环的[m.n]环番的第一个例子。含反式-15，16-二甲基-二氢芘单元（14 π）和Paudler的8b，8 c-二氮杂环戊二烯并[fg]苊烯（12 π）的双层轮烯萘的合成正在进行中。利用MNDO-PM 3方法，通过光谱性质和理论计算，研究了轮烯芳环的结构和跨环π-π相互作用.

It is our interest to study how two pi-systems mutually interact when they overlap each other in a close proximity. According to the frontier molecular orbital calculations, Greenberg et al. predicted a destabilizing pi-pi interaction in a (4n+2)pi-(4n+2)pi system, a stabilizing interaction in a (4n+2)pi-(4n)pi system, and greater stabilization in a (4n)pi-(4n)pi system than in the (4n+2)pi-(4n)pi system. To verify this interesting prediction experimentally, we considered that [3.3]annulenophanes must be the most suitable models since [3.3]cyclophane permits exact evaluation of pi-pi interaction without interference of the strain effect.As model compounds for the study of (4n+2)(4n+2)interaction (n*2), we synthesized [3.3]cyclophanes containing Vogel's 1,6-methano[10]annulene, which are the first example of [m.n]cyclophanes containing two annulene rings. The synthesis of double-layered annulenophanes containing trans-15,16-dimethyl-dihydropyrene units (14pi) and Paudler's 8b,8c-diazacyclopent[fg]acenaphthylene (12pi) is in progress. The structures and transannular pi-pi interactions of annuleno-phanes were studies based on the spectral properties and theoretical calculations by the MNDO-PM3 method.