Indaphyrins, pyrrole-modified porphyrins containing a cleaved pyrrole β,β'-bond and two annulated indanone moieties, possess unusually broadened and redshifted UV/Vis spectra because of their π-expanded chromophores. The parent free base indaphyrin has been crystallographically characterized, highlighting its strongly ruffled conformation incorporating a helimeric twist. It was shown to be susceptible to regiospecific derivatizations at the opposite side of the ring-cleaved pyrrole (dihydroxylation, followed by functional group transformations of the resulting diol functionality), generating indaphyrin-based chlorin analogues, indachlorins, that incorporate a dihydroxypyrroline, pyrrolindione, oxazolone, or a morpholine moiety. Structural modifications resulted in further broadening and hyper- and bathochromic shifts of the optical spectra, some of which possess a nearly panchromatic absorption between 300 to well above 900 nm. The extents to which these modifications affect their solid-state conformations were analyzed.
Keywords: UV/Vis spectroscopy; X-ray diffaction; chromophores; macrocycles; porphyrinoids.
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