Binaphthanol-derived emitters with aggregation-induced emission, acidochromic and chiral optical properties

Abstract

The development of chiral organic fluorescent molecules has attracted broad attention for their various optical applications. In this work, four pairs of chiral fluorescent molecules based on binaphthanol structure have been designed and synthesized. These molecules show blue fluorescent emission in organic solvents with good fluorescent quantum yields and large Stokes shifts. The molecules with benzoxazole moiety display aggregation-induced emission effect in methanol/water solutions, while molecules with quinazolinone moiety show aggregation-caused quenching properties. Moreover, compounds with quinazolinone moiety exhibit acidochromic properties in aqueous solution with different pH values, and their emission intensity are significantly enhanced in strongly acidic conditions. The chiral molecules generally have good circular dichroism intensity. Their R- and S- enantiomers show mirror-imaged circular dichroism curves. Further studies reveal that compound with mono quinazolinone moiety has specific aggregation-induced circular dichroism enhancement properties. This work provides a new strategy for obtaining chiral BINOL-based fluorescent molecules with unique optical properties.