Synthesis and Spectral Properties of meso-Arylbacteriochlorins, Including Insights into Essential Motifs of their Hydrodipyrrin Precursors
AbstractSynthetic bacteriochlorins—analogues of bacteriochlorophylls, Nature’s near-infrared absorbers—are attractive for diverse photochemical studies. meso-Arylbacteriochlorins have been prepared by the self-condensation of a dihydrodipyrrin–carbinol or dihydrodipyrrin–acetal following an Eastern-Western (E-W) or Northern-Southern (N-S) joining process. The bacteriochlorins bear a gem-dimethyl group in each pyrroline ring to ensure stability toward oxidation. The two routes differ in the location of the gem-dimethyl group at the respective 3- or 2-position in the dihydrodipyrrin, and the method of synthesis of the dihydrodipyrrin. Treatment of a known 3,3-dimethyldihydrodipyrrin-1-carboxaldehyde with an aryl Grignard reagent afforded the dihydrodipyrrin-1-(aryl)carbinol, and upon subsequent acetylation, the corresponding dihydrodipyrrin-1-methyl acetate (dihydrodipyrrin–acetate). Self-condensation of the dihydrodipyrrin–acetate gave a meso-diarylbacteriochlorin (E-W route). A 2,2-dimethyl-5-aryldihydrodipyrrin-1-(aryl)carbinol underwent self-condensation to give a trans-A2B2-type meso-tetraarylbacteriochlorin (N-S route). In each case, the aromatization process entails a 2e−/2H+ (aerobic) dehydrogenative oxidation following the dihydrodipyrrin self-condensation. Comparison of a tetrahydrodipyrrin–acetal (0%) versus a dihydrodipyrrin–acetal (41%) in bacteriochlorin formation and results with various 1-substituted dihydrodipyrrins revealed the importance of resonance stabilization of the reactive hydrodipyrrin intermediate. Altogether 10 new dihydrodipyrrins and five new bacteriochlorins have been prepared. The bacteriochlorins exhibit characteristic bacteriochlorophyll-like absorption spectra, including a Qy band in the region 726–743 nm. View Full-Text
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Reddy, M.N.; Zhang, S.; Kim, H.-J.; Mass, O.; Taniguchi, M.; Lindsey, J.S. Synthesis and Spectral Properties of meso-Arylbacteriochlorins, Including Insights into Essential Motifs of their Hydrodipyrrin Precursors. Molecules 2017, 22, 634.
Reddy MN, Zhang S, Kim H-J, Mass O, Taniguchi M, Lindsey JS. Synthesis and Spectral Properties of meso-Arylbacteriochlorins, Including Insights into Essential Motifs of their Hydrodipyrrin Precursors. Molecules. 2017; 22(4):634.Chicago/Turabian Style
Reddy, Muthyala N.; Zhang, Shaofei; Kim, Han-Je; Mass, Olga; Taniguchi, Masahiko; Lindsey, Jonathan S. 2017. "Synthesis and Spectral Properties of meso-Arylbacteriochlorins, Including Insights into Essential Motifs of their Hydrodipyrrin Precursors." Molecules 22, no. 4: 634.
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