Cyclic Acetylenes. X. A Transannular Hypochromism Observed in a Cyclic Diacetylene Containing a Naphthalene Nucleus
作者:Takashi Ando、Masazumi Nakagawa
DOI:10.1246/bcsj.40.363
日期:1967.2
A cyclic diacetylene (XIa) has been synthesized by the oxidative coupling of 1, 5-bis(propargyloxymethyl)naphthalene (X) with a cyclic dimer (XIb) and a cyclic trimer (XIc). The electronic spectra of XIb and XIc have been found to be almost identical with that of naphthalene with respect to the location of the absorption maxima and the intensities. On the other hand, a marked decrease in the absorption intensities has been observed in the spectrum of the cyclic monomer (XIa). An inspection of the Dreiding model of XIa indicates that the two conformations (A and B) can retain the maximum distance between the dyine unit and the naphthalene nucleus. On the basis of the molecular model, the distance between the two chromophores and the angle between the short axis of the nucleus and the bridging chain have been estimated to be 2.26 Å, 21° for A and 2.12 Åand 38° for B. Employing these data, the hypochromic effect exerted by the diyne chromophore on the absorption of the naphthalene nucleus has been calculated according to the theory of Tinoco and Rhodes, resulting in a fairly good agreement with the observed values. Inversely, the calculation of the distance and the angle between the two chromophoric groups using the observed hypochromic effect has also given reasonable values. Therefore, the hypochromism observed in the cyclic diacetylene (XIa) has been attributed to the operation of dispersion-force interaction between diyne unit and the naphthalene chromophore.
通过1,5-双(丙炔氧甲基)萘(X)与环状二聚体(XIb)和环状三聚体(XIc)的氧化耦合反应,合成了一种环状二炔(XIa)。研究发现,XIb和XIc的电子光谱与萘的吸收最大位置和强度几乎相同。另一方面,在环状单体(XIa)的光谱中观察到了明显的吸收强度下降。对XIa的Dreiding模型的检查表明,两种构象(A和B)能够保持二炔单元和萘核之间的最大距离。基于分子模型,估计了两个发色团之间的距离和核短轴与桥链之间的角度,分别为A的2.26 Å和21°,B的2.12 Å和38°。利用这些数据,根据Tinoco和Rhodes的理论计算了二炔发色团对萘核吸收的减色效应,结果与观察值相当一致。相反,使用观察到的减色效应计算两个发色团之间的距离和角度也给出了合理值。因此,观察到的环状二炔(XIa)的减色效应归因于二炔单元和萘发色团之间的色散力相互作用。