The nature of the sensitiser substituent determines quenching sensitivity and protein affinity and influences the design of emissive lanthanide complexes as optical probes for intracellular use

Introduction of different substituents at the 7-position of a sensitising azaxanthone group in a series of emissive Eu and Tb complexes can determine the intracellular uptake and distribution profile and may be linked to modulation of protein affinity.