Unprecedented four-way-output molecular response system based on biphenyl-2,2′-diyldiacridiniums: induction of axial chirality through intramolecular hydrogen bonds between chiral amide groups

Upon the attachment of N-(R)-2-phenylethylamide moieties to the acridinium units of the title dication, intramolecular hydrogen bonds induce a diastereomeric preference in terms of axial chirality (70% de at −40 °C in CH2Cl2). Thus, external stimuli induce not only UV–vis and fluorescence spectra changes but also changes in the CD and fluorescence-detected CD (FDCD) spectra, realizing unprecedented four-way-output molecular response systems.