Locked π-Expanded Chlorins in Two Steps from Simple Tetraarylporphyrins

Abstract

[reaction: see text] Upon tandem Reformatsky reaction, easily accessible porphyrinic ketones give "locked" chlorinic diester. Both ketones and diesters, as bases or palladium complexes, efficiently generate singlet dioxygen, as demonstrated by trapping with cholesterol.

β‐meso‐Annulated meso‐Tetraarylchlorins: A Study of the Effect of Ring Fusion on Chlorin Conformation and Optical Spectra

“…We can thus conclude that in order to have intense red‐shifted absorption bands in napthoporphyrins, the position of the keto group is crucial, whereby β’‐location is the preferred choice. Overall, this was a useful synthetic development towards preparation of suitably tuned conformationally locked napthoporphyriniods on account of its high yielding reaction sequence …”

“…The same observation also holds true when we compare the free base analogues to each other (compounds 24 H 2 and 7 ). However, in Scheme when we compare the naphthochlorins with the precursor β’‐keto napthoporphyrins ( 23 Ni and 23 H 2 ), in all cases the later are more red‐shifted (Q x =714 nm for 23 Ni and Q x =724 nm for 23 H 2 ) than their chlorin analogues . Another noteworthy point is, that the β’‐keto napthoporphryin 23 Ni is more red‐shifted than the 1 st generation keto napthoporphyrin (Scheme , compound 4 Ni ; Q x =649 nm).…”

“…The reaction proceeded via first addition of one equivalent of the reagent, followed by Zn(II) induced dehydroxylation of the adduct. This gave rise to a stable porphyrin cation, which added a second equivalent of the reagent . The free base derivatives of the porphyrin 23 H 2 and chlorin diester 24 H 2 were also prepared, through Ni‐demetallation, and use of Zn(II) as a removable template, as depicted in Scheme .…”

“…The third example of a ring‐fused chlorin was reported by Callot et al. in 2005 . The well‐known Reformatsky reaction was utilized to obtain napthofused diester chlorin 24 Ni and 24 Pd .…”

Synthesis, Characterization, and Electrochemical Studies of New π‐Extended Metalloporphyrins

“…To check if these compounds might be useful as sensitizers, their ability to oxidize cholesterol was verified under irradiation. [11] The efficiency of the newly obtained sensitizers was compared with the well-known tetraphenylporphyrin (H 2 TPP) and all the results are summarized in Table 1 (see the Supporting Information for details). Because these metalloporphyrins have an external basic site (the nitrogen atom of the fused quinoline), their electronic spectra were expected to change in the presence of acid.…”