Design, synthesis and redox properties of a fluorene platform linking two different Bodipy dyes

Several new fluorophores have been prepared by grafting boradiazaindacene (red absorbing) and/or styrylboradiazaindacene (blue absorbing) units as terminal energy acceptors onto a fluorene-derived platform. In one case, an amino-bis(bipyridine) pocket has been attached to enable strong binding of transition metal ions. The stepwise syntheses were largely based on Pd-catalysed cross-coupling reactions. The electrochemistry of the dyes has been analysed by reference to the properties of the various synthetic intermediates, protonation of the tertiary amine site present in the bis(bipyridine) species enabling processes involving this centre to be distinguished from those associated with the boradiazaindacene (Bodipy) unit.