Variation at the 3’ position of fluorescein via Suzuki–Miyaura cross-coupling with aryl and heteroaryl
moieties gave a family of anthofluoresceins whose spectroscopic properties were studied. The 1-methylindole
derivative gave the highest quantum yield and was observed to behave as a molecular rotor, displaying
marked variations in fluorescent intensities with viscosity and offering possible application in
cellular sensing and fluorescent polarisation assays.