摘要
重新测量了对称-四嗪(1,2,4,5-tetrazine,Sym-Tz)和3,6-二甲基对称-四嗪(3,6-dimethyl-1,2,4,5-tetrazine,DM-sym-Tz)的紫外-可见(UV-Vis)电子吸收光谱。与气相比较,由于静电极化效应,在非极性环己烷溶剂中ππ*带和nπ*带均向红移。2种化合物表现出典型的溶致变色行为,即随着溶剂极性的增加,ππ*带向红移,而nπ*带向蓝移,这是静电极化效应与更强的溶质-溶剂相互作用,如取向极化溶剂效应,甚至氢键作用平衡的结果。而且,nπ*光谱带与ππ*带各自具有完整吸收带而没有相互重叠。作为分析化学教材中溶剂效应的典型案例,从非极性环己烷到强极性水,可以同时展示溶剂极性对ππ*和nπ*2个吸收带的影响。通过计算化学,展示了nπ*带精细结构对应的振动模式。作为本科生甚至研究生光谱学实验教学内容,操作简单,伴随着明显的肉眼可见的颜色变化,从气相的淡紫红色,到环己烷中紫红色,水中红色,这更可能引起学生对溶剂效应的学习兴趣。
The UV-Vis absorption spectra of symmetric tetrazine(1,2,4,5-tetrazine,Sym-Tz)and 3,6-dimethyl-1,2,4,5-tetrazine(DM-sym-Tz)were remeasured.Compared with those in vapor,both ππ* and nπ* bands in non-polar cyclohexane produce red-shift due to the electrostatic polarization effect.The two compounds exhibit typical solvatochromism behavior,that is,as the solvent polarity increases,the ππ*band undergoes a red shift and the nπ* band produces a blue shift,resulting from the equilibrium between electrostatic polarization and stronger solute-solvent interaction,for example,orientation polarization effect,or even hydrogen bonding.Moreover,the nπ* and ππ* bands exhibit complete absorption spectra without overlapping with each other.As a typical example of solvent effects in analytical chemistry textbooks,from non-polar cyclohexane to strongly polar water,the influence of solvent polarity on both the ππ* and nπ* absorption bands can be demonstrated simultaneously.By computational chemistry,the vibration modes corresponding to the fine structure of nπ* bands were demonstrated.As a teaching content of spectroscopy experiments for undergraduate and even graduate,it is easy to operate and accompanied by obvious visible color changes,from light purple in the vapor phase to purple red in cyclohexane and red in water,which is more likely to arouse interest of students in learning solvent effects.
作者
周慧
任列香
王中慧
刘红云
晋卫军
ZHOU Hui;REN Lie-Xiang;WANG Zhong-Hui;LIU Hong-Yun;JIN Wei-Jun(Department of Chemical and Material Engineering,Lyuliang University,Lishi 033000,China;College of Chemistry,Beijing Normal University,Beijing 100875,China)
出处
《化学教育(中英文)》
北大核心
2025年第16期54-62,共9页
Chinese Journal of Chemical Education
基金
山西省2022年度应用型地方本科院校分析化学PBL教学课堂改革研究项目(J20221159)
山西省教育厅新建地方应用型本科院校化工与材料专业(群)人才培养体系建设实践与研究项目(J2020359)
北京师范大学“十四五”期间高等教育领域教材建设项目资助课题。
