Effect of bromine substituent on optical properties of aryl compounds |
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Authors: | Chao‐Zhi Zhang Ting Li Yang Yuan Cheng‐Yue Gu Meng‐Xiao Niu Hui Cao |
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Institution: | 1. Department of Chemistry, Nanjing University of Information Science and Technology, Nanjing, China;2. Jiangsu Key Laboratory of Atmospheric Environment Monitoring and Pollution Control, Nanjing University of Information Science and Technology, Nanjing, China |
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Abstract: | Substituents significantly affect optical properties of organic compounds. In this study, a series of organic compounds were synthesized. Ultraviolet‐visible and cyclic voltammetry spectra were determined. The relationships between the number of π electron in an aryl ring and the redshift (and molecular orbital energy levels) were studied. To investigate mechanisms of the bromine substituent effects, theoretical calculations were carried out. Ultraviolet‐visible spectra of bromine‐containing compounds exhibit obvious redshifts (0.04‐0.17 eV) of the maximal absorption wavelengths and enhanced absorbance (11%‐57%) compared with corresponding reference compounds. The lowest unoccupied and highest occupied molecular orbital energy levels of compounds containing bromine substituents are 0.05 to 0.60 and 0.02 to 0.40 eV lower than that of corresponding reference compounds. On the whole, the redshifts and the reduced molecular orbital energy levels caused by bromine substituent decrease with the increase in the number of π electron in an aryl ring. The effects would be attributed to strong p‐π conjugation between p electron in the bromine substituent and π electrons in aryl rings. Therefore, this paper suggests a useful way for tuning optical absorption and molecular orbital energy levels of aryl compounds. |
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Keywords: | bromine molecular orbital energy level optical property redshift substituent effect |
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