Effects of Substituents on Synthetic Analogs of Chlorophylls. Part 4: How Formyl Group Location Dictates the Spectral Properties of Chlorophylls b, d and f

Yuen, Jonathan M.; Harris, Michelle A.; Liu, Mengran; Diers, James R.; Kirmaier, Christine; Bocian, David F.; Lindsey, Jonathan S.; Holten, Dewey

doi:10.1111/php.12401

Cited by 20 publications

(40 citation statements)

References 46 publications

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“…This approach is useful for comparing relative peak-intensity changes for related tetrapyrroles, and overcomes some of the drawbacks with other normalization methods or using (uncertain) extinction coefficients. 76 Each absorption spectrum contains three main features: the strong near-ultraviolet (NUV) Soret bands (B x and B y , 410–445 nm), a very weak green-orange Q x band (520–560 nm) and a red or NIR Q y band (609–706 nm). The Soret and Q y band positions are listed in Table 1.…”

Section: Resultsmentioning

confidence: 99%

Bioconjugatable, PEGylated hydroporphyrins for photochemistry and photomedicine. Narrow-band, red-emitting chlorins

et al. 2016

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Chromophores that absorb and emit in the red spectral region (600–700 nm), are water soluble, and bear a bioconjugatable tether are relatively rare yet would fulfill many applications in photochemistry and photomedicine. Here, three molecular designs have been developed wherein stable synthetic chlorins – analogues of chlorophylls – have been tailored with PEG groups for use in aqueous solution. The designs differ with regard to order of the installation (pre/post-formation of the chlorin macrocycle) and position of the PEG groups. Six PEGylated synthetic chlorins (three free bases, three zinc chelates) have been prepared, of which four are equipped with a bioconjugatable (carboxylic acid) tether. The most effective design for aqueous solubilization entails facial encumbrance where PEG groups project above and below the plane of the hydrophobic disk-like chlorin macrocycle. The chlorins possess strong absorption at ~400 nm (B band) and in the red region (Qy band); regardless of wavelength of excitation, emission occurs in the red region. Excitation in the ~400 nm region thus provides an effective Stokes shift of >200 nm. The four bioconjugatable water-soluble chlorins exhibit Qy absorption/emission in water at 613/614, 636/638, 698/700 and 706/710 nm. The spectral properties are essentially unchanged in DMF and water for the facially encumbered chlorins, which also exhibit narrow Qy absorption and emission bands (full-width-at-half maximum of each <25 nm). The water-solubility was assessed by absorption spectroscopy over the concentration range ~0.4 μM – 0.4 mM. One chlorin was conjugated to a mouse polyclonal IgG antibody for use in flow cytometry with compensation beads for proof-of-principle. The conjugate displayed a sharp signal when excited by a violet laser (405 nm) with emission in the 620–660 nm range. Taken together, the designs described herein augur well for development of a set of spectrally distinct chlorins with relatively sharp bands in the red region.

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Section: Resultsmentioning

confidence: 99%

Bioconjugatable, PEGylated hydroporphyrins for photochemistry and photomedicine. Narrow-band, red-emitting chlorins

et al. 2016

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“…Indeed, access to the 2, 255,296,298,299 3, 265,290,298,299 5, 254,256,269 7, 277,283,2908,277 10, 254,256,269 12, 255,284,299 13, 265,286,289,299 15, 263,270,283,286,299 17, 257,270,299 18, 257 and 20 263,283 positions has been achieved, as has installation of the isocyclic ring 267,289 (and 6-membered imide analogues 286,300 ) characteristic of native chlorophylls. The following sections describe novel chlorin architectures obtained chiefly by application of aforementioned methodology for (1) precursor synthesis, (2) macrocycle formation, and (3) bromination of the chlorin macrocycle under neutral or acidic conditions.…”

Section: Smorgasbord Of Chlorinsmentioning

confidence: 99%

“…Similar spectral trends were observed for the zinc chelates of this series of formylchlorins. 298 The slightly larger bathochromic shift and hyperchromic effect of the 3-formylchlorin versus the 2-formylchlorin provide data for comparison with native chlorophylls such as chlorophyll f , which contains the 2-formyl-3-vinyl substituent pattern (Scheme 2). A deeper understanding of the origin of the substituent effects that engender the spectral properties of chlorophyll f likely will require synthesis of chlorins bearing combinations of multiple auxochromes, including not only the 2-formyl and 3-vinyl groups (and vice versa) but also the isocyclic ring.…”

Section: Smorgasbord Of Chlorinsmentioning

confidence: 99%

De NovoSynthesis of Gem-Dialkyl Chlorophyll Analogues for Probing and Emulating Our Green World

2015

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Woodward reported his infamous synthesis of chlorin e 6 trimethyl ester, a known synthetic precursor to chlorophyll a. [59][60][61][62][63][64]124 The work was posited on a half-century of intensive studies by many investigators in tetrapyrrole chemistry and began a decade after the close of Fischer's lifetime of research 125−128 (which included an uncompleted synthetic program directed toward chlorophylls 15 ). Indeed, "he read all the umpteen papers on the chlorophylls written by Willstaẗter and Fischer, including the experimental parts." 129 The Woodward synthesis of chlorin e 6 trimethyl ester required 46 steps, of which 24 were spent on converting the sole precursor, Knorr's pyrrole, to the four pyrroles destined to form rings A−D; 7 additional steps accrued to obtain the dipyrromethanes that constitute the Eastern and Western halves (Scheme 13, the step numbers are identical to those shown in ref 64.). The first step formed the Knorr pyrrole (in several kg quantities), the next 24 steps were divided into four parallel paths, whereas the remaining 21 steps proceeded in linear fashion. Remarkable features of the synthesis include the directed intramolecular joining (via an imine) of the Eastern and Western halves (step 33), construction of the acrylate Scheme 10. Hydrogenation of a Porphyrin to Form a Chlorin Scheme 11. Representative meso-Tetraarylchlorins Scheme 12. Methyl Pyropheophorbide a

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“…2 is normalized to the total intensity (300–1000 nm) obtained by integration when plotted in wavenumbers (cm −1 ), which is convenient for comparing effects of substituents on relative band intensities. 40 …”

Section: Resultsmentioning

confidence: 99%

Bioconjugatable, PEGylated hydroporphyrins for photochemistry and photomedicine. Narrow-band, near-infrared-emitting bacteriochlorins

et al. 2016

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Synthetic bacteriochlorins absorb in the near-infrared (NIR) region and are versatile analogues of natural bacteriochlorophylls. The utilization of these chromophores in energy sciences and photomedicine requires the ability to tailor their physicochemical properties, including the incorporation of units to impart water solubility. Herein, we report the synthesis, from two common bacteriochlorin building blocks, of five wavelength-tunable, bioconjugatable and water-soluble bacteriochlorins along with two non-bioconjugatable benchmarks. Each bacteriochlorin bears short polyethylene glycol (PEG) units as the water-solubilizing motif. The PEG groups are located at the 3,5-positions of aryl groups at the pyrrolic β-positions to suppress aggregation in aqueous media. A handle containing a single carboxylic acid is incorporated to allow bioconjugation. The seven water-soluble bacteriochlorins in water display Qy absorption into the NIR range (679–819 nm), sharp emission (21–36 nm full-width-at-half-maximum) and modest fluorescence quantum yield (0.017–0.13). Each bacteriochlorin is neutral (non-ionic) yet soluble in organic (e.g., CH2Cl2, DMF) and aqueous solutions. Water solubility was assessed using absorption spectroscopy by changing the concentration ∼1000-fold (190–690 µM to 0.19–0.69 µM) with a reciprocal change in pathlength (0.1–10 cm). All bacteriochlorins showed excellent solubility in water, except for a bacteriochlorin–imide that gave slight aggregation at higher concentrations. One bacteriochlorin was conjugated to a mouse polyclonal IgG antibody for use in flow cytometry with compensation beads for proof-of-principle. The antibody conjugate of B2-NHS displayed a sharp signal upon ultraviolet laser excitation (355 nm) with NIR emission measured with a 730/45 nm bandpass filter. Overall, the study gives access to a set of water-soluble bacteriochlorins with desirable photophysical properties for use in multiple fields.

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Effects of Substituents on Synthetic Analogs of Chlorophylls. Part 4: How Formyl Group Location Dictates the Spectral Properties of Chlorophylls b, d and f

Cited by 20 publications

References 46 publications

Bioconjugatable, PEGylated hydroporphyrins for photochemistry and photomedicine. Narrow-band, red-emitting chlorins

Bioconjugatable, PEGylated hydroporphyrins for photochemistry and photomedicine. Narrow-band, red-emitting chlorins

De NovoSynthesis of Gem-Dialkyl Chlorophyll Analogues for Probing and Emulating Our Green World

Bioconjugatable, PEGylated hydroporphyrins for photochemistry and photomedicine. Narrow-band, near-infrared-emitting bacteriochlorins

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