Experiment of Solvation Effects on Absorption Spectra of Sym-Tetrazine and 3,6-Dimethyl-Sym-Tetrazine in Analytical Chemistry Textbooks
ZHOU Hui1, REN Lie-Xiang1, WANG Zhong-Hui1**, LIU Hong-Yun2**, JIN Wei-Jun2**
1. Department of Chemical and Material Engineering,Lyuliang University,Lishi 033000,China; 2. College of Chemistry,Beijing Normal University,Beijing 100875,China
Abstract 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.
ZHOU Hui, REN Lie-Xiang, WANG Zhong-Hui, LIU Hong-Yun, JIN Wei-Jun. Experiment of Solvation Effects on Absorption Spectra of Sym-Tetrazine and 3,6-Dimethyl-Sym-Tetrazine in Analytical Chemistry Textbooks[J]. Chinese Journal of Chemical Education, 2025, 46(16): 54-62.
