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).