有机化合物电子光谱中的助色基及其作用机理探讨(Ⅰ)

• 作 者: 蒋龙平 王颖 李润卿 李娜 周维义
• 机 构: 天津大学材料科学与工程学院,天津大学材料科学与工程学院,天津大学材料科学与工程学院,天津大学材料科学与工程学院,天津大学材料科学与工程学院 天津300072,天津300072,天津300072,天津3
• 出 处: 光谱学与光谱分析
• 发表日期: 2003年01期
• 关键词: 紫外-可见光谱 助色基 p-π共轭效应 超共轭效应

本文就电子光谱中助色基的作用进行了讨论 ,认为不能一概地认为助色基能使与之相连的生色基最大吸收波长统统发生红移 ,而应具体问题具体分析 :对于n→π 来说 ,一方面助色基的p轨道和生色基的最低π 反键空轨道相互作用 ,使π 反键轨道能量上升 ,另一方面助色基的p轨道和生色基的n轨道正交 ,n轨道能量基本保持不变 ,因此n→π 跃迁能增加 ,吸收波长发生蓝移。对于π→π 跃迁来说 ,助色基的p轨道和生色基的最高π成键轨道相互作用生成的新的最高π成键轨道 ,能量虽然有所升高 ,但升高的程度与π 反键轨道升高的程度相比 ,在一些化合物中π轨道升高程度较大 ,因而π→π 跃迁能减小 ,吸收波长发生红移 ;在另一些化合物中π轨道升高程度较小 ,因而π→π 跃迁能增加 ,吸收波长发生蓝移。

In this paper, the role of the auxiliary color-based in the electronic spectrum is discussed. It can not be considered that the auxiliary chromophore can redshift the maximum wavelength of the chromophore to which it is connected. However, the specific problems should be analyzed. For n → π , On the one hand, the p-orbital of the achromatic group interacts with the lowest π-anti-null orbit of the chromophore so that the π-antibonding orbital energy increases. On the other hand, the p- At the intersection of n and the intersection of orbit and the intersection of energy and basic invariable, so n → π transition can increase, blue shift of absorption wavelength. For the π → π transition, the new highest π bond orbitals generated by the interaction between the p-orbital of the anodizing group and the highest π-bonded orbital of the chromophore are increased in energy, but the degree of increase is proportional to π In some compounds, the orbital increase is larger than that of the antibonding orbital, so the π → π transition energy decreases and the absorption wavelength shifts redshift. In other compounds, the π orbit elevation is smaller, Thus π → π transition can increase, the absorption wavelength blue shift.