Novel bipyrazolo[1,5-a]pyridine luminogens with aggregation-induced emission enhancement properties

Abstract

A novel 3,3′-bipyrazolo[1,5-a]pyridine molecular scaffold was obtained as a product of serendipity. Both photophysical characterisations and HOMO–LUMO theoretical calculations indicate its potential as a promising fluorophore with notable intramolecular charge transfer. Nonetheless, the emission properties of this compound suffer from the typical aggregation-caused quenching effect. To overcome this situation, we introduced additional diaryl groups onto the skeleton and synthesised a series of 7,7′-diaryl-3,3′-bipyrazolo[1,5-a]pyridines via palladium-catalysed intermolecular C–H/C–H bond cross-coupling reaction in 35–62% yields. This series of tailor-made luminogens with twisted π-structures display aggregation-induced emission enhancement properties.