Synthesis of boron-dipyrromethene–ferrocene conjugates

Synthesis, spectral, electrochemical and photophysical properties of four BODIPY–ferrocene conjugates in which one or two ferrocenyl groups were covalently connected either directly to boron-dipyrromethene framework or to meso-phenyl group of boron-dipyrromethene unit are described. The BODIPY–ferrocene conjugates were prepared by adopting different synthetic routes. The absorption studies indicated the presence of charge transfer band in BODIPY–ferrocene conjugates in which the ferrocenyl group(s) were directly connected to boron-dipyrromethene framework. The electrochemical studies on conjugates indicated that ferrocenyl group was difficult to oxidize whereas boron-dipyrromethene unit was easier to reduce. The conjugates were non-fluorescent due to electron transfer from ferrocene to boron-dipyrromethene unit. However, when ferrocene was oxidized to ferrocenium ion with an oxidizing agent, the conjugates exhibited fluorescence with decent quantum yields (0.17–0.31) and lifetimes (3.8–5.2 ns).