Stimuli-responsive emission of quinoxalinone-based compounds. From experimental findings to theoretical insight by means of multiscale computational spectroscopy approaches

The drastic differences in absorption spectra of structurally close quinoxalinone derivatives, containing electrondonor and -acceptor units, are rationalized, by means of theoretical tools. They are ascribed to the difference in the intramolecular charge-transfer character of the electronic transition corresponding to the experimental longest-wavelength absorption bands of these systems. Charge-transfer compounds are not luminescent in solutions, in contrast to their analogs with weaker charge-separation and longer pi-conjugated backbone, which suggests that the main factor switching-off' emission is related to their push-pull properties and the balance between the length of the pi-conjugated backbone and the donor-acceptor strength. Furthermore, the protonation of the studied quinoxalinones is shown to result in a weakening of the donor-acceptor strengths and conjugation efficiency, thus limiting charge-transfer and producing the emission response in the acidified solutions.

Automated summary

The study shows that drastic differences in absorption spectra of structurally close quinoxalinone derivatives can be rationalized using theoretical tools. Protonation weakens the donor-acceptor strengths, limits charge-transfer, and leads to emission response in acidified solutions.