Developing ideal IR probes is essential to understand the structure and dynamics of biomolecules with time-resolved IR spectroscopies and imaging techniques. Especially, nitrile (CN) group has recently been proposed to serve as IR probes of the local environment of proteins. Herein, we investigated the effect of a substituent on the vibrational properties of the benzonitrile. The electron-donating and withdrawing character of p-substituent on benzonitrile are expected to modulate the vibrational frequency, molar extinction coefficient, and vibrational lifetime of CN probe. FT-IR revealed the positive correlation between electron-donating character and the molar extinction coefficient of CN stretch mode. Infrared pump-probe (IR-PP) measurements showed that the vibrational lifetime of CN stretch mode exhibits a relatively weak correlation with the electron-donating strength. Among the investigated samples, 4-dimethylamino benzonitrile with the strongest electron-donating strength shows enhanced absorption and extended vibrational lifetime. Utilizing substituent effects will be a practical strategy to improve the performance of the IR probe.
Bibliographical noteFunding Information:
This research was supported by a grant from the Institute for Basic Science (IBS‐R023‐D1) and by the National Research Foundation of Korea (NRF) grant funded by the Korea government (MSIT) (NRF‐2020R1A5A1019141).
© 2021 Wiley-VCH GmbH
- Electron-donating effect
- IR probes
- Peptides and proteins
- Time-resolved IR spectroscopy
ASJC Scopus subject areas
- Organic Chemistry