Sparsely substituted chlorins as core constructs in chlorophyll analogue chemistry. Part 3: Spectral and structural properties

Taniguchi, Masahiko; Ptaszek, Marcin; McDowell, Brian E.; Boyle, Paul D.; Lindsey, Jonathan S.

doi:10.1016/j.tet.2007.02.040

Cited by 65 publications

(80 citation statements)

References 51 publications

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“…The spectra are normalized at the Q y band; the path length of the sample cell and FWHM of the Q y band are also listed in the inset. The concentrations are based on the absorbance of the ~5 μM solution measured at the B band (assuming 64 ε = 160,000 M −1 cm −1 ).…”

Section: Figmentioning

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: Figmentioning

confidence: 99%

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

et al. 2016

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“…This result matches well with a previous 1 H NMR spectroscopic study of analogous meso-bromo substituted chlorins, wherein a downfield shift (0.32 ppm) was observed of the β-pyrrolic proton adjacent to the meso-bromo substituent. 16 Introduction of a bromine atom at the β-position causes the resonances from adjacent mesoprotons (H 5 or H 15 ) to shift upfield (∼0.16 ppm for H-BC-Br 3 or H-BC-Br 3 Br 13 ). In addition, the resonances from the adjacent p-tolyl protons (H 2a or H 12a ) are shifted upfield (∼0.1 ppm) versus that of H-BC.…”

Section: Halogenation Of Bacteriochlorinsmentioning

confidence: 99%

Regioselective 15-Bromination and Functionalization of a Stable Synthetic Bacteriochlorin

2007

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8,18, undergoes regioselective electrophilic bromination with NBS to give the 15-bromo analogue (MeO-BC-Br 15 ) in 85% yield. By contrast, the bacteriochlorin lacking the 5-methoxy group (8,8,18,18-tetramethyl-2,12-di-p-tolylbacteriochlorin, H-BC) gives a mixture of two mono-bromo and two dibromobacteriochlorins. Deuterium exchange of both bacteriochlorins (H-BC and MeO-BC) in acidic media (TFA-d) occurs preferentially at the β-pyrrole positions (3, 13) > unhindered meso-positions (5, 15 for H-BC; 15 for MeO-BC) > hindered meso-positions (10, 20). The 15-bromo-5-methoxybacteriochlorin MeO-BC-Br 15 was subjected to three types of Pd-mediated coupling reactions (Suzuki, Sonogashira, Hartwig-Buchwald) to give six bacteriochlorins bearing functional groups at the 15-position (49% to 85% yield). The groups include 4-(tert-butoxycarbonylmethoxy) phenyl, 3, phenylethynyl,. The presence of the 15-ethynyl moiety shifts the position of the long-wavelength Q y band from 732 nm to ∼753 nm. The ability to introduce a range of groups at a specific site enables synthetic bacteriochlorins to be tailored for a variety of applications.

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“…In parallel with the progressive bathochromic shift of the Q y band position, the relative intensity of the Q y band also increased (i.e., I B /I Q decreased from 4.3 to 2.5). The 603-nm absorption band of the methoxychlorin ( ZnC-25 ) is identical to that of the corresponding zinc chlorin that lacks any substituents, not even the 10-mesityl group ( ZnC-27 ) [77]. We have not determined the molar absorption coefficient of the various chlorins but instead rely on the I B /I Q ratio to indicate the relative intensity of long-wavelength absorption, which can be reliably determined regardless of sample quantity.…”

Section: Resultsmentioning

confidence: 99%

“…The introduction of auxochromes, chiefly at the 3,13-positions, enables the long-wavelength Q y band to be tuned from 603 nm to 715 nm [21,77]. Attempts to employ a previously unexamined set of potential auxochromes (methoxy, dimethylamino, methylthio, phenanthryl, p -substituted phenyl, and oligomeric ethynylphenyl substituents) led to establishment of valuable data concerning structure versus spectral properties but did not enlarge the spectral window for wavelength tuning with chlorins.…”

Section: Discussionmentioning

confidence: 99%

Progress towards synthetic chlorins with graded polarity, conjugatable substituents, and wavelength tunability

Gauger

Muthukumaran

et al. 2015

J. Porphyrins Phthalocyanines

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Advances in chlorin synthetic chemistry now enable the de novo preparation of diverse chlorin-containing molecular architectures. Five distinct molecular designs have been explored here, including hydrophobic bioconjugatable (oxo)chlorins; a hydrophilic bioconjugatable chlorin; a trans-ethynyl/iodochlorin building block; a set of chlorins bearing electron-rich (methoxy, dimethylamino, methylthio) groups at the 3-position; and a set of ten 3,13-disubstituted chlorins chiefly bearing groups with extended π-moieties. Altogether 23 new chlorins (17 targets, 6 intermediates) have been prepared. The challenge associated with molecular designs that encompass the combination of “hydrophilic, bioconjugatable and wavelength-tunable” chiefly resides in the nature of the hydrophilic unit.

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Sparsely substituted chlorins as core constructs in chlorophyll analogue chemistry. Part 3: Spectral and structural properties

Cited by 65 publications

References 51 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

Regioselective 15-Bromination and Functionalization of a Stable Synthetic Bacteriochlorin

Progress towards synthetic chlorins with graded polarity, conjugatable substituents, and wavelength tunability

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