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.

Indachlorins: Nonplanar Indanone‐Annulated Chlorin Analogues with Panchromatic Absorption Spectra between 300 and 900 nm

“…Furthermore, the extremely nonplanar 18 π‐chromophores of the indachlorins highlight the conformational plasticity of the porphyrinic macrocycle without it losing its key properties of aromaticity and associated high‐extinction UV/Vis spectra. The generally high solubility (in organic solvents) of the indaphyrins also differentiates them from a number of other π‐extended systems 14c. We attribute this apparent lack of stacking to their flexible and nonplanar conformations.…”

Porphyrin Macrocycle Modification: Pyrrole Ring-Contracted or -Expanded Porphyrinoids

“…Treatment of the free-base oxime 55 (M = 2H) with p -TSA in toluene at reflux leads to the formation of quinoline-annulated porphyrins [73,74].…”

Unsymmetrical Bisquinolines with High Potency against P. falciparum Malaria

“…In addition to PPQ itself, a wide range of other bis-4-aminoquinoline compounds have been shown to have antiplasmodial activity, tending to be active against both chloroquine-sensitive (CQS) and CQR strains [17,19,[30][31][32][33][34][35][36][37][38][39][40]. During the 1990s, a study of bis-quinolines by Vennerstrom and co-workers led to the discovery of Ro 48-6910, which was evaluated in preclinical studies but was regrettably found to be phototoxic [19,37,[41][42][43][44].…”