Selective Extraction, Recovery, and Sensing of Hydroquinone Mediated by a Supramolecular Pillar[5]quinone Quinhydrone Charge-Transfer Complex

Intermolecular
interactions between an electron-rich aromatic hydroquinone
(HQ) with its electron deficient counterpart, benzoquinone (BQ), result
in the formation of a quinhydrone charge-transfer complex. Herein,
we report a novel quinhydrone-type complex between pillar[5]­quinone
(P[5]­Q) and HQ. Characterized by a suite of spectroscopic techniques
including 1H NMR, UV–visible, and FTIR together
with PXRD, SEM, BET, CV, and DFT modeling studies, the stability of
the complex is determined to be due to an electron–proton transfer
reaction coupled with a complementary donor–acceptor interaction.
The selectivity of P[5]­Q toward HQ over other dihydroxybenzene isomers
allows for not only the naked-eye detection of HQ but also its selective
liquid–liquid extraction and recovery from aqueous media.