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A series of porphyrinoids fused to highly electron-withdrawing bis(thiadiazolo)benzene units have been prepared and spectroscopically characterized. These structures have modified chromophores and exhibit large bathochromic shifts. The nickel(II), copper(II) and zinc complexes of a bis(thiadiazolo)benzoporphyrin were prepared, and these showed strong absorptions above 600 nm that shifted to longer wavelengths with increasing atomic number for the coordinated metal cations. Although the investigated porphyrinoids were poorly soluble, proton NMR data could be obtained, and these demonstrated that the structures possess global aromatic character. This was confirmed with nucleus-independent chemical shift (NICS) calculations and anisotropy of induced current density (AICD) plots. The AICD plots also demonstrate that the fused heterocyclic unit is disconnected from the porphyrinoid π-system, and in this respect, it differs from phenanthroline-fused porphyrinoids as it shows the presence of extended conjugation pathways.
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This content will become publicly available on January 10, 2026
Synthesis, Protonation and Aromatic Characteristics of a Series of 1,10-Phenanthroline-Fused Porphyrinoids
A series of porphyrin analogues with fused 1,10-phenanthroline units were synthesized. The proton NMR spectra for phenanthroline-fused heteroporphyrins showed significantly upfield shifted meso-proton resonances compared to related porphyrinoid systems and the peaks corresponding to alkyl substituents directly attached to these macrocycles were also observed further upfield. These results indicate that the presence of the phenanthroline unit leads to reduced diatropicity, but the internal NH resonance was also further upfield, a result that is inconsistent with this interpretation. A phenanthrene-fused carbaporphyrin gave an unexpectedly upfield singlet for the internal C−H at nearly −9 ppm, while the NH protons appeared at −6.8 ppm. These unusual chemical shifts again imply enhanced diatropicity but the reduced downfield shifts for the external protons indicates that the aromatic ring current has been significantly reduced. Similar results were obtained for phenanthroline-fused oxybenzi- and oxypyriporphyrins. Detailed analyses of the spectroscopic properties for these systems are reported and protonation studies were conducted. The conjugation pathways and aromatic properties were computationally analyzed using nucleus independent chemical shifts (NICS) and anisotropy of induced current density plots.
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- Award ID(s):
- 2247214
- PAR ID:
- 10620576
- Publisher / Repository:
- American Chemical Society
- Date Published:
- Journal Name:
- The Journal of Organic Chemistry
- Volume:
- 90
- Issue:
- 1
- ISSN:
- 0022-3263
- Page Range / eLocation ID:
- 8 to 29
- Subject(s) / Keyword(s):
- 9,10-phenanthroline NMR spectroscopy aromaticity electron-deficient heterocyclic
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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