Toward a New Family of Bifunctional Organoiron Dendrimers: Facile Synthesis, Redox, and Photophysical Fingerprints

Multifunctional macromolecules continue to attract attention. Here, three generations of a new family of bifunctional organoiron dendrimers are reported, which are synthesized from a redox-active organoiron complex, eta(6)-dichlorobenzene-eta(5)-cyclopentadienyl-iron(II). The facile chemistry of the complex is exploited to functionalize the dendritic peripheral with photoactive beta-naphthol, yielding redox, photoactive dendrimers under mild conditions. To ascertain the redox and photophysical fingerprints of these dendrimers, cyclic voltammetric, and UV-vis and fluorescence spectroscopic measurements are used. The cyclic voltammetric measurements suggest non-interacting redox-active iron centers within the dendritic structure, and a negative dendritic effect on the half-wave potential. The cathodic peak broadens with increasing dendrimer generation as the rate of electron transfer between the electrode and the iron centers decreases. The dendrimers exhibit the characteristic absorption and fluorescence fingerprint of beta-naphthol and a positive dendritic effect on the fluorescence intensities. A 24 h UV irradiation of acetonitrile/chloroform solution of the dendrimers yields their organic analogues with a concomitant enhancement of the absorption and fluorescence properties. The synthetic approach to these dendrimers offers an attractive route to other redox, multifunctional organometallic dendrimers.