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.