Integration of Cyanine, Merocyanine and Styryl Dye Motifs with Synthetic Bacteriochlorins. (18th December 2015)

• Record Type: Journal Article
• Authors: Yang, Eunkyung; Zhang, Nuonuo; Krayer, Michael; Taniguchi, Masahiko; Diers, James R.; Kirmaier, Christine; Lindsey, Jonathan S.; Bocian, David F.; Holten, Dewey
• Is Part Of: Photochemistry and photobiology. Volume 92:Number 1(2016)
• Page Start: 111
• Page End: 125
• Publication Date: 2015-12-18
• Subjects: Photochemistry -- Periodicals; Light -- Physiological effect -- Periodicals; 541.35
• DOI: 10.1111/php.12547
• Languages: English
• ISSNs: 0031-8655

Abstract

Abstract: Understanding the effects of substituents on spectral properties is essential for the rational design of tailored bacteriochlorins for light‐harvesting and other applications. Toward this goal, three new bacteriochlorins containing previously unexplored conjugating substituents have been prepared and characterized. The conjugating substituents include two positively charged species, 2‐( N ‐ethyl 2‐quinolinium)vinyl‐ (B‐1) and 2‐( N ‐ethyl 4‐pyridinium)vinyl‐ (B‐2), and a neutral group, acroleinyl‐ (B‐3); the charged species resemble cyanine (or styryl) dye motifs whereas the neutral unit resembles a merocyanine dye motif. The three bacteriochlorins are examined by static and time‐resolved absorption and emission spectroscopy and density functional theoretical calculations. B‐1 and B‐2 have Q y absorption bathochromically shifted well into the NIR region (822 and 852 nm), farther than B‐3 (793 nm) and other 3, 13‐disubstituted bacteriochlorins studied previously. B‐1 and B‐2 have broad Q y absorption and fluorescence features with large peak separation (Stokes shift), low fluorescence yields, and shortened S1 ( Q y ) excited‐state lifetimes (~700 ps and ~100 ps). More typical spectra and S1 lifetime (~2.3 ns) are found for B‐3. The combined photophysical and molecular‐orbital characteristics suggest the altered spectra and enhanced nonradiative S1 decay of B‐1 and B‐2 derive from excited‐state configurations in which electron density is shifted between the macrocycle and the substituents. Abstract : The photophysical properties (Φf, τs, ΦT, τT, kf, kic, kisc ) of three free base bacteriochlorins bearing previously unexplored conjugating substituents have been characterized and interpreted with the aid of molecular‐orbital calculations. The bacteriochlorins absorb strongly in the 780–850 nm region and provide models for photosynthetic bacteriochlorophylls.