Synthesis and Characterization of Ferrocenyl Chlorins, 1,1′-Ferrocene-Linked Chlorin Dimers, and their BODIPY Analogues

We present the synthesis
and characterization of meso-ferrocenyl-substituted hydroporphyrins
(chlorins) and 1,1′-linked chlorin dimers. The dipyrromethane
chlorin precursors were also transformed into Fc-substituted BODIPYs
and 1,1′-ferrocenyl-linked BODIPY dimers. The chlorin dimers
were studied by 1D and 2D NMR experiments and DFT calculations, which
showed that their solution structures were dependent on the central
metal. Monomeric and dimeric Ni­(II) chlorins had similar 1H NMR spectra. Monomeric and dimeric free base, Zn­(II), and Pd­(II)
chlorins, on the other hand, showed significantly more different spectra.
The eclipsed conformer of the free base chlorin dimer was calculated
to be energetically more favored than the open form. The chlorin and
BODIPY fluorescence emissions were quenched in the Fc-substituted
compounds; these could be recovered by oxidation of the Fe­(II) center.
Cyclic voltammetry showed up to five oxidation waves for the free
base chlorin dimer, which suggests that the macrocycles were not behaving
independently of each other.