Investigation of the Vibrational Characteristics of 6-Isocyano-1-Methyl-1H-Indole: Utilizing the Isonitrile Group as an Infrared Probe

Indole derivatives have garnered considerable attention in the realm of biochemistry due to their multifaceted properties. In this study, we undertake a systematic investigation of the vibrational characteristics of a model indole derivative, 6-isocyano-1-methyl-1H-indole (6ICMI), by employing a combination of FTIR, IR pump-probe spectroscopy, and theoretical calculations. Our findings demonstrate a strong dependence of the isonitrile stretching frequency of 6ICMI on the polarizability of protic solvents and the density of hydrogen-bond donor groups in the solvent when the isonitrile group is bonded to aromatic groups. Both experimental and theoretical analyses unveil a significant correlation between the isonitrile stretch vibration of 6ICMI and the solvent acceptor number of alcohols. Furthermore, the polarization-controlled infrared pump-probe conducted on 6ICMI in dimethyl sulfoxide provides additional support for the potential use of the isonitrile stretching mode of 6ICMI as an effective infrared probe for local environments.

Automated summary

In this study, the vibrational characteristics of a model indole derivative, 6-isocyano-1-methyl-1H-indole (6ICMI), were systematically investigated using FTIR, IR pump-probe spectroscopy, and theoretical calculations. The study found that the isonitrile stretching frequency of 6ICMI strongly depends on the polarizability of protic solvents and the density of hydrogen-bond donor groups in the solvent when the isonitrile group is bonded to aromatic groups. Experimental and theoretical analyses revealed a significant correlation between the isonitrile stretch vibration of 6ICMI and the solvent acceptor number of alcohols. Additionally, polarization-controlled infrared pump-probe experiments in dimethyl sulfoxide supported the potential use of the isonitrile stretching mode of 6ICMI as an effective infrared probe for local environments.