Small Panchromatic and NIR Absorbers from Quinoid Zwitterions

The transamination of oxoaminobenzoquinonemonoimine (BQI derivatives), an unconventional zwitterionic quinone, allows isolating a series of compounds featuring electron-donating aryl auxochromes. The substitution has a very strong impact on the electrochemical and optical features, which is rationalized by theoretical calculations. Protonation and alkylation of the BQIs towards the corresponding cations lead to surprising redshifts of the absorption, especially in the instance of the most electron-rich dyes which exhibit panchromatic absorption spanning up to the near-infrared (NIR) region, a remarkable achievement for such small molecules.