Structural and Photophysical Characterization of All Five Constitutional Isomers of the Octaethyl-β,β'-dioxo-bacterio- and -isobacteriochlorin Series.

Abstract

It is well-known that treatment of β-octaethylporphyrin with H2 O2 /conc. H2 SO4 converts it to a β-oxochlorin as well as all five constitutional isomers of the corresponding β,β'-dioxo-derivatives: two bacteriochlorin-type isomers (β-oxo groups at opposite pyrrolic building blocks) and three isobacteriochlorin-type isomers (β-oxo-groups at adjacent pyrrolic building blocks). By virtue of the presence of the strongly electronically coupled β-oxo auxochromes, none of the chromophores are archetypical chlorins, bacteriochlorins, or isobacteriochlorins. Here the authors present, inter alia, the single crystal X-ray structures of all free-base diketone isomers and a comparative description of their UV-vis absorption spectra in neutral and acidic solutions, and fluorescence emission and singlet oxygen photosensitization properties, Magnetic Circular Dichroism (MCD) spectra, and singlet excited state lifetimes. DFT computations uncover underlying tautomeric equilibria and electronic interactions controlling their electronic properties, adding to the understanding of porphyrinoids carrying β-oxo functionalities. This comparative study lays the basis for their further study and utilization.

• Authors: Christian Brückner, Nivedita Chaudhri, Dustin E Nevonen, Sayantan Bhattacharya, Arthur Graf, Elizabeth Kaesmann, Ruoshi Li, Matthew J Guberman-Pfeffer, Tomoyasu Mani, Arunpatcha Nimthong-Roldán, Matthias Zeller, Adrien A P Chauvet, Victor Nemykin
• Journal: Chemistry (Weinheim an der Bergstrasse, Germany) (Chemistry) Vol. 27 Issue 65 Pg. 16189-16203 (Nov 22 2021) ISSN: 1521-3765 [Electronic] Germany
• PMID: 34535932 (Publication Type: Journal Article)
• Copyright: © 2021 Wiley-VCH GmbH.

Chemical References

• Porphyrins
• Pyrroles
• isobacteriochlorin

Topics

• Fluorescence
• Isomerism
• Molecular Structure
• Porphyrins
• Pyrroles