Synthesis and charge-transfer dynamics in a ferrocene-containing organoboryl aza-bodipy donor-acceptor triad with boron as the hub

A N,N′-bis(ferroceneacetylene)boryl complex of 3,3′-diphenylazadiisoindolylmethene was synthesized by the reaction of an N,N′-difluoroboryl complex of 3,3′-diphenylazadiisoindolylmethene and ferroceneacetylene magnesium bromide. The novel diiron complex was characterized by a variety of spectroscopic techniques, electrochemistry, and ultrafast time-resolved methods. Spectroscopy and redox behavior was correlated with the density functional theory (DFT) and time-dependent DFT calculations. An unexpected degree of coupling between the two Fc ligands was observed. Despite a lack of conjugation between the donor and acceptor, the complex undergoes very rapid (τ = 1.7 ± 0.1 ps) photoinduced intramolecular charge separation followed by subpicosecond charge recombination to form a triplet state with a lifetime of 4.8 ± 0.1 μs.