title: Mono- and Bisquinoline-Annulated Porphyrins from Porphyrin β,β'-Dione Oximes.
abstract: An acid-induced reaction of meso-tetraphenyl-2-hydroxyimino-3-oxoporphyrin leads, with concomitant loss of water, to a formal electrophilic aromatic substitution of the ortho-position of the phenyl group adjacent to the oxime, forming a quinoline moiety. Owing in part to the presence of a π-extended chromophore, the resulting meso-triphenylmonoquinoline-annulated porphyrin (λmax = 750 nm) possesses a much altered optical spectrum from that of the starting oxime (λmax = 667 nm). An oxidative DDQ-induced ring-closure process is also possible, generating the corresponding meso-triphenylmonoquinoline-annulated porphyrin quinoline N-oxide, possessing a slightly shifted and sharpened UV-vis spectrum (λmax = 737 nm). The connectivity of the chromophores was conclusively shown by NMR spectroscopy. Both ketone functionalities in meso-tetraphenyl-2,3-dioxoporphyrin can be converted, via the oxime and using the acid- or oxidant-induced reaction pathways, either in one step or in a stepwise fashion, to bisquinoline-annulated porphyrin (λmax = 775 nm) and its N-oxide (λmax = 779 nm), respectively. This process is complementary to a previously established pathway toward bisquinoline-annulated porphyrins. Their zinc(II), nickel(II), and palladium(II) complexes are also described. Several examples of the quinoline-annulated porphyrins were crystallographically characterized, proving their connectivity and showing their conformations that are extremely distorted from planarity. The work presents a full account on the synthesis, structure, and spectroscopic properties of these classes of NIR-absorbing dyes.
authors.affiliation: †Department of Chemistry, University of Connecticut, Storrs, Connecticut 06269-3060, United States.
authors.forename: Joshua
authors.initials: J
authors.lastname: Akhigbe
authors.affiliation: †Department of Chemistry, University of Connecticut, Storrs, Connecticut 06269-3060, United States.
authors.forename: Michael
authors.initials: M
authors.lastname: Luciano
authors.affiliation: ‡Department of Chemistry, Youngstown State University, One University Plaza, Youngstown, Ohio 44555-3663, United States.
authors.forename: Matthias
authors.initials: M
authors.lastname: Zeller
authors.affiliation: †Department of Chemistry, University of Connecticut, Storrs, Connecticut 06269-3060, United States.
authors.forename: Christian
authors.initials: C
authors.lastname: Brückner
mesh_terms: D015394:Molecular Structure; D010091:Oximes / Q000737:chemistry*; D011166:Porphyrins / Q000138:chemical synthesis / Q000737:chemistry*; D011804:Quinolines / Q000737:chemistry*
chemical_list: D010091:Oximes; D011166:Porphyrins; D011804:Quinolines