Metal-Stabilized Quinoidal Dibenzo[ g, p]chrysene-Fused Bis-dicarbacorrole System

Xian Sheng Ke, Yongseok Hong, Vincent M. Lynch, Dongho Kim, Jonathan L. Sessler

Research output: Contribution to journalArticle

15 Citations (Scopus)

Abstract

We report here a metal complexation-based strategy that permits access to a highly stable expanded porphyrin-type quinoidal polycyclic aromatic hydrocarbons (PAH). Specifically, double insertion of Pd(II) ions into a dibenzo[g,p]chrysene-fused bis-dicarbacorrole (bis-H3) gives rise to a bis-metalated species (bis-Pd) that undergoes a facile benzenoid-quinonoid transformation. In contrast to what is true for the corresponding mono-Pd(II) complex, which has organic radical character, well resolved 1H NMR and 19F NMR spectra are seen for bis-Pd. This complex is also electron paramagnetic resonance (EPR) silent over a range of temperatures. On the basis of crystallographic analyses, Raman spectroscopic studies, harmonic oscillator model of aromaticity (HOMA), and nucleus-independent chemical shift (NICS) calculations, we suggest that the dibenzo[g, p]chrysene bridge in bis-Pd has quinoidal character and that the system as a whole is a closed shell species. As expected for a quinoidal system, bis-Pd is characterized by a lowest energy absorption band that is shifted into the NIR (λmax = ca. 1420 nm (ϵ > 1.5 × 105 M-1 cm-1) for bis-Pd vs 780 nm (ϵ < 5.0 × 103 M-1 cm-1) for bis-H3). On the other hand, bis-Pd displays solvent dependent ground state and transient absorption spectral features. Such findings provide support for a zwitterionic resonance contribution to what is a predominantly a quinonoid-type ground state. The use of specific metalation to fine-tune the electronic features of polytopic ligands, as reported here, opens the door to what might be a potentially generalizable approach to the design of quinoidal PAH structures with long wavelength solvatochromic absorption features.

Original languageEnglish
Pages (from-to)7579-7586
Number of pages8
JournalJournal of the American Chemical Society
Volume140
Issue number24
DOIs
Publication statusPublished - 2018 Jun 20

All Science Journal Classification (ASJC) codes

  • Catalysis
  • Chemistry(all)
  • Biochemistry
  • Colloid and Surface Chemistry

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