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Christian Brückner - One of the best experts on this subject based on the ideXlab platform.
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Oxidations of chromene-annulated Chlorins.
Organic & biomolecular chemistry, 2017Co-Authors: Nisansala Hewage, Matthias Zeller, Christian BrücknerAbstract:A chromene-annulated Chlorin is a meso-pentafluorophenyl-2,3-dihydroxyChlorin in which one of the hydroxy groups is linked to the ortho-position of a flanking meso-aryl group, thereby forming an annulated chromene moiety; the second hydroxy group is unprotected. This report illustrates the oxidation chemistry of the chromene-annulated Chlorin under a number of different oxidation conditions. In some reactions, chromene annulation is retained and the non-protected alcohol is oxidized, generating Chlorin-like chromophores carrying pyrroline β-carbons in oxidation states between those found in typical porphyrins and Chlorins. Other products have lost the chromene moiety. The reactivity of the pyrroline carbon with respect to undergoing radical chemistry is shown with the formation of a number of products following a Swern oxidation, including the formation of two directly linked pyrroline-pyrroline and pyrroline-pyrrole Chlorin dimers. This work contributes to the further understanding of the chemistry of Chlorins. Selected compounds possess functionalities at their periphery susceptible to nucleophilic attack by MeOH, suggesting their use as chemosensors.
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magnetic circular dichroism spectroscopy of meso tetraphenylporphyrin derived hydroporphyrins and pyrrole modified porphyrins
Journal of Physical Chemistry A, 2016Co-Authors: Hannah M. Rhoda, Joshua Akhigbe, Christian Brückner, Junichi Ogikubo, Jared R. Sabin, Christopher J. Ziegler, Victor N. NemykinAbstract:A large set of free-base and transition-metal 5,10,15,20-tetraphenyl-substituted Chlorins, bacterioChlorins, and isobacterioChlorins and their pyrrole-modified analogues were investigated by combined UV–visible spectroscopy, magnetic circular dichroism (MCD), density functional theory (DFT), and time-dependent DFT (TDDFT) approaches and their spectral characteristics were compared to those of the parent compounds, free-base tetraphenylporphyrin 1H2 and Chlorin 2H2. It was shown that the nature of the pyrroline substituents in the Chlorin derivatives dictates their specific UV–vis and MCD spectroscopic signatures. In all hydroporphyrin-like cases, MCD spectroscopy suggests that the ΔHOMO is smaller than the ΔLUMO for the macrocycle-centered frontier molecular orbitals. DFT and TDDFT calculations were able to explain the large broadening of the UV–vis and MCD spectra of the Chlorin diones and their derivatives compared to the other hydroporphyrins and hydroporphyrin analogues. This study contributes to the ...
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Quinoline-annulated Chlorins and Chlorin-analogs
Journal of Porphyrins and Phthalocyanines, 2016Co-Authors: Joshua Akhigbe, Mengxi Yang, Michael Luciano, Christian BrücknerAbstract:The OsO4-mediated dihydroxylation of quinoline-annulated porphyrin generates a quinoline-annulated dihydroxyChlorin in a regioselective fashion. Its dihydroxypyrroline moiety, located at the opposite of the annulated pyrrole, is susceptible to the same functional group interconversions we previously demonstrated for non-annulated dihydroxyChlorins: oxidations to the corresponding dione, lactone, and dialkoxymorpholine derivatives. The quinoline-annulated Chlorin and derivatives are all characterized by absorption spectra that are much broadened and between 130 and 220 nm red-shifted compared to their non-annulated analogs. Absorbance maxima in the NIR up to well above 800 nm were recorded. We attribute the bathochromic shift to their extended [Formula: see text]-systems and inferred non-planarity, highlighting that quinoline-annulation is a particularly effective and simple strategy to red-shift the absorption spectra of Chlorins and Chlorin analogs.
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Quinoline-annulated Chlorins and Chlorin-analogs
Journal of Porphyrins and Phthalocyanines, 2016Co-Authors: Joshua Akhigbe, Mengxi Yang, Michael Luciano, Christian BrücknerAbstract:The OsO4-mediated dihydroxylation of quinoline-annulated porphyrin generates a quinoline-annulated dihydroxyChlorin in a regioselective fashion. Its dihydroxypyrroline moiety, located at the opposite of the annulated pyrrole, is susceptible to the same functional group interconversions we previously demonstrated for non-annulated dihydroxyChlorins: oxidations to the corresponding dione, lactone, and dialkoxymorpholine derivatives. The quinoline-annulated Chlorin and derivatives are all characterized by absorption spectra that are much broadened and between 130 and 220 nm red-shifted compared to their non-annulated analogs. Absorbance maxima in the NIR up to well above 800 nm were recorded. We attribute the bathochromic shift to their extended π-systems and inferred non-planarity, highlighting that quinoline-annulation is a particularly effective and simple strategy to red-shift the absorption spectra of Chlorins and Chlorin analogs.
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Chromene-Annulated BacterioChlorins
The Journal of organic chemistry, 2016Co-Authors: Michael A Hyland, Nisansala Hewage, Matthias Zeller, Kimberly Panther, Arunpatcha Nimthong-roldán, Milinda Samaraweera, José A. Gascón, Christian BrücknerAbstract:Syntheses and optical properties of mono- and bis-chromene-annulated bacterioChlorins are described. Known monochromene-annulated meso-(pentafluorophenyl)Chlorin is susceptible to a regioselective OsO4-mediated dihydroxylation, generating two monochromene-annulated trihydroxybacterioChlorin stereoisomers: either the newly introduced vic-cis-diol functionality is on the same side as the vic-cis-diol moiety the chromene-annulation was based on or on the opposite side. Treatment of the two isomers with heat or base generates different sets of bis-chromene-annulated bacterioChlorin stereo- and regioisomers. Detailed 1D and 2D (1)H and (19)F NMR spectroscopic investigations allowed the characterization of the isomers that formed. The regioselectivity of the second annulation reaction was rationalized computationally on steric grounds. The bacterioChlorin-type optical spectra of the mono- and bis-chromene-annulated bacterioChlorins are modulated as a result of the annulation, with each isomer possessing a unique spectrum, attributed to the effects the regiochemically distinct annulations have on the conformation of the chromophore. The formation of a bis-chromene-annulated Chlorin from the bacterioChlorins is also described, including its X-ray crystal structure, revealing some details of the metrics of the chromene-annulated moiety. The vic-diol functionality of monochromene-annulated trihydroxybacterioChlorins is also susceptible to oxidation and ring-expansion reactions, generating chromene-annulated pyrrole-modified Chlorins incorporating oxazolone and morpholine moieties. The work expands the body of work on the synthesis and optical fine-tuning of meso-aryl-substituted bacterioChlorins.
Jonathan S Lindsey - One of the best experts on this subject based on the ideXlab platform.
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synthetic Chlorins possible surrogates for chlorophylls prepared by derivatization of porphyrins
Chemical Reviews, 2017Co-Authors: Masahiko Taniguchi, Jonathan S LindseyAbstract:Chlorophylls make Earth green, are the central constituents in the engine of photosynthesis, and not surprisingly have garnered immense attention. A Chlorin, the core chromophore of a chlorophyll, is a dihydroporphyrin macrocycle that contains one pyrroline ring and three pyrrole rings. The dominant method for the synthesis of Chlorins has entailed the derivatization of porphyrins. The present review covers the ostensibly simple conversion of porphyrins, regardless of synthetic or biological origin, to Chlorins. The period covered encompasses the entire history since the beginnings of Chlorin synthetic chemistry in the early 20th century through 2015. Representative transformations include hydrogenation, cycloaddition, annulation, and diverse “breaking and mending” approaches. Altogether, the synthesis of >1000 Chlorins or Chlorin-like compounds (containing >50 distinct pyrroline motifs) is described. Such diversity animates the question “what structural features are essential for a Chlorin to resemble ch...
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Photophysical Properties and Electronic Structure of Chlorin-Imides: Bridging the Gap between Chlorins and BacterioChlorins
The journal of physical chemistry. B, 2015Co-Authors: Kaitlyn M Faries, Michael Krayer, Dorothee Lahaye, Marcin Ptaszek, James R. Diers, Christine Kirmaier, Masahiko Taniguchi, Joseph W Springer, Eunkyung Yang, Jonathan S LindseyAbstract:Efficient light harvesting for molecular-based solar-conversion systems requires absorbers that span the photon-rich red and near-infrared (NIR) regions of the solar spectrum. Reported herein are the photophysical properties of a set of six Chlorin-imides and nine synthetic Chlorin analogues that extend the absorption deeper (624–714 nm) into these key spectral regions. These absorbers help bridge the gap between typical Chlorins and bacterioChlorins. The new compounds have high fluorescence quantum yields (0.15–0.34) and long singlet excited-state lifetimes (4.2–10.9 ns). The bathochromic shift in Qy absorption is driven by substituent-based stabilization of the lowest unoccupied molecular orbital, with the largest shifts for Chlorins that bear an electron-withdrawing, conjugative group at the 3-position in combination with a 13,15-imide ring.
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Photophysical properties and electronic structure of retinylidene-Chlorin-chalcones and analogues.
Photochemical & photobiological sciences : Official journal of the European Photochemistry Association and the European Society for Photobiology, 2014Co-Authors: Joseph W Springer, Michael Krayer, Jonathan S Lindsey, James R. Diers, David F. Bocian, Masahiko Taniguchi, Christian Ruzié, Dariusz M. Niedzwiedzki, Dewey HoltenAbstract:Synthetic Chlorins can accommodate diverse substituents about the macrocycle perimeter. Simple auxochromes (e.g., vinyl, acetyl, phenyl) allow systematic tuning of spectral and photophysical features. More extensive spectral tailoring may be achieved by using more potent, highly conjugated substituents that themselves bring new absorption into a target spectral region, if deleterious excited-state quenching processes can be avoided. To explore such an expanded substituent space, herein the spectral and photophysical properties of four Chlorin–chalcones are reported. The molecules are free base and zinc Chlorins with substituents at the 13-position that include a chalcone and an extended chalcone derived by reaction of the 13-acetylChlorin with benzaldehyde and all-trans-retinal, respectively. Measurements of the spectral and photophysical properties (Φf, τs, kf, kic, kisc) are accompanied by density functional calculations that examine the characteristics of the frontier molecular orbitals. The Chlorin–chalcones in nonpolar (toluene) and polar (dimethylsulfoxide) media exhibit bathochromically shifted (and intense) Qy absorption bands. The presence of the retinylidene group adds new absorption in the blue-green region where the Chlorins are typically transparent; excitation in this region leads to quantitative formation of the Chlorin Qy excited state. The spectral properties generally correlate with substituent effects on the frontier MOs. The four Chlorin–chalcones in the solvent toluene have high fluorescence yields (0.24–0.30) and multi-nanosecond singlet excited-state lifetimes (3.7–8.4 ns), in addition to the added absorption imparted by the chalcone moiety. Collectively, the studies reported herein provide insight into the fundamental properties of Chlorins and illustrate the utility of chalcones as a means of both tuning and augmenting the spectral properties of these chromophores.
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structural characteristics that make chlorophylls green interplay of hydrocarbon skeleton and substituents
New Journal of Chemistry, 2011Co-Authors: Olga Mass, Marcin Ptaszek, James R. Diers, David F. Bocian, Dewey Holten, Masahiko Taniguchi, Joseph W Springer, Kaitlyn M Faries, Jonathan S LindseyAbstract:Understanding the effects of substituents on natural photosynthetic pigments is essential for gaining a deep understanding of why such pigments were selected over the course of evolution for use in photosynthetic systems. This knowledge should provide for a more thoughtful design of artificial light-harvesting systems. The hydrocarbon skeleton of all chlorophylls is phorbine, which contains an annulated five-membered (isocyclic) ring in addition to the reduced pyrrole ring characteristic of Chlorins. A phorbine and a 131-oxophorbine (which bears an oxo group in the isocyclic ring) were synthesized as benchmark molecules for fundamental spectral and photophysical studies. The phorbine and 131-oxophorbine macrocycles lack peripheral substituents other than a geminal dimethyl group in the reduced ring to stabilize the Chlorin chromophore. The spectral properties and electronic structure of the zinc or free base 131-oxophorbine closely resemble those of the corresponding analogues of chlorophyll a. Accordingly, the fundamental electronic properties of chlorophylls are primarily a consequence of the 131-oxophorbine base macrocycle.
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De Novo Synthesis of Long-Wavelength Absorbing Chlorin-13,15-dicarboximides
Journal of Organic Chemistry, 2010Co-Authors: Marcin Ptaszek, Michael Krayer, Dorothee Lahaye, C Muthiah, Jonathan S LindseyAbstract:Chlorins bearing a six-membered imide ring spanning positions 13−15, commonly referred to as purpurinimides, exhibit long-wavelength absorption yet have heretofore only been available via semisynthesis from naturally occurring chlorophylls. A concise route to synthetic Chlorins, which bear a geminal dimethyl group in the pyrroline ring, has been extended to provide access to Chlorin-13,15-dicarboximides. The new route entails (i) synthesis of a 13-bromoChlorin, (ii) palladium-catalyzed carbamoylation at the 13-position, (iii) regioselective 15-bromination under acidic conditions, and (iv) one-flask palladium-mediated carbonylation and ring closure to form the imide. In some cases the ring closure reaction afforded the isomeric (and readily separable) Chlorin−isoimide in addition to the Chlorin−imide. The resulting Chlorin−imides and Chlorin−isoimides exhibit long-wavelength absorption (679−715 nm) and emission (683−720 nm) in the far-red and near-infrared spectral region. The absorption of the Chlorin−(is...
K. Eszter Borbas - One of the best experts on this subject based on the ideXlab platform.
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Synthesis and Characterization of Ferrocenyl Chlorins, 1,1'-Ferrocene-Linked Chlorin Dimers, and their BODIPY Analogues.
Inorganic chemistry, 2017Co-Authors: Anna I. Arkhypchuk, Andreas Orthaber, K. Eszter BorbasAbstract:We present the synthesis and characterization of meso-ferrocenyl-substituted hydroporphyrins (Chlorins) and 1,1′-linked Chlorin dimers. The dipyrromethane Chlorin precursors were also transformed into Fc-substituted BODIPYs and 1,1′-ferrocenyl-linked BODIPY dimers. The Chlorin dimers were studied by 1D and 2D NMR experiments and DFT calculations, which showed that their solution structures were dependent on the central metal. Monomeric and dimeric Ni(II) Chlorins had similar 1H NMR spectra. Monomeric and dimeric free base, Zn(II), and Pd(II) Chlorins, on the other hand, showed significantly more different spectra. The eclipsed conformer of the free base Chlorin dimer was calculated to be energetically more favored than the open form. The Chlorin and BODIPY fluorescence emissions were quenched in the Fc-substituted compounds; these could be recovered by oxidation of the Fe(II) center. Cyclic voltammetry showed up to five oxidation waves for the free base Chlorin dimer, which suggests that the macrocycles w...
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Synthesis of Chlorin-sensitized near infrared-emitting lanthanide complexes.
Inorganic chemistry, 2012Co-Authors: Johanna Laakso, Geraldine A. Rosser, Csongor Szíjjártó, Andrew Beeby, K. Eszter BorbasAbstract:Lanthanide (Yb3+, Nd3+) complexes equipped with red-absorbing hydroporphyrin (Chlorin) antennae were synthesized and characterized. The syntheses are scalable, highly modular, and enable the introduction of different Chlorins functionalized with a single reactive group (COOH or NH2). Absorption maxima were dependent on Chlorin substitution pattern (monomeso aryl or dimeso aryl) and metalation state (free base or zinc chelate). The complexes benefit from dual Chlorin (610-639 nm) and lanthanide (980 or 1065 nm for Yb- or Nd-complexes, respectively) emission in the biologically relevant red and near IR region of the spectrum.
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Design, synthesis, and photophysical characterization of water-soluble Chlorins.
The Journal of organic chemistry, 2008Co-Authors: K. Eszter Borbas, Dewey Holten, Hooi Ling Kee, Vanampally Chandrashaker, Chinnasamy Muthiah, Jonathan S LindseyAbstract:The use of Chlorins as photosensitizers or fluorophores in a range of biological applications requires facile provisions for imparting high water solubility. Two free base Chlorins have been prepared wherein each Chlorin bears a geminal dimethyl group in the reduced ring and a water-solubilizing unit at the Chlorin 10-position. In one design (FbC1-PO3H2), the water-solubilizing unit is a 1,5-diphosphonopent-3-yl (“swallowtail”) unit, which has previously been used to good effect with porphyrins. In the other design (FbC2-PO3H2), the water-solubilizing unit is a 2,6-bis(phosphonomethoxy)phenyl unit. Two complementary routes were developed for preparing FbC2-PO3H2 that entail introduction of the protected phosphonate moieties either in the Eastern-half precursor to the Chlorin or by derivatization of an intact Chlorin. Water-solubilization is achieved in the last step of each synthesis upon removal of the phosphonate protecting groups. The Chlorins FbC1-PO3H2 and FbC2-PO3H2 are highly water-soluble (>10 mM)...
Michael A Hyland - One of the best experts on this subject based on the ideXlab platform.
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Chromene-Annulated BacterioChlorins
The Journal of organic chemistry, 2016Co-Authors: Michael A Hyland, Nisansala Hewage, Matthias Zeller, Kimberly Panther, Arunpatcha Nimthong-roldán, Milinda Samaraweera, José A. Gascón, Christian BrücknerAbstract:Syntheses and optical properties of mono- and bis-chromene-annulated bacterioChlorins are described. Known monochromene-annulated meso-(pentafluorophenyl)Chlorin is susceptible to a regioselective OsO4-mediated dihydroxylation, generating two monochromene-annulated trihydroxybacterioChlorin stereoisomers: either the newly introduced vic-cis-diol functionality is on the same side as the vic-cis-diol moiety the chromene-annulation was based on or on the opposite side. Treatment of the two isomers with heat or base generates different sets of bis-chromene-annulated bacterioChlorin stereo- and regioisomers. Detailed 1D and 2D (1)H and (19)F NMR spectroscopic investigations allowed the characterization of the isomers that formed. The regioselectivity of the second annulation reaction was rationalized computationally on steric grounds. The bacterioChlorin-type optical spectra of the mono- and bis-chromene-annulated bacterioChlorins are modulated as a result of the annulation, with each isomer possessing a unique spectrum, attributed to the effects the regiochemically distinct annulations have on the conformation of the chromophore. The formation of a bis-chromene-annulated Chlorin from the bacterioChlorins is also described, including its X-ray crystal structure, revealing some details of the metrics of the chromene-annulated moiety. The vic-diol functionality of monochromene-annulated trihydroxybacterioChlorins is also susceptible to oxidation and ring-expansion reactions, generating chromene-annulated pyrrole-modified Chlorins incorporating oxazolone and morpholine moieties. The work expands the body of work on the synthesis and optical fine-tuning of meso-aryl-substituted bacterioChlorins.
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meso tetrakis pentafluorophenyl porphyrin derived chromene annulated Chlorins
Journal of Organic Chemistry, 2012Co-Authors: Michael A Hyland, Martha D Morton, Christian BrücknerAbstract:The synthesis of mono- and bis-chromene-annulated meso-(pentafluorophenyl)Chlorins from meso-tetrakis(pentafluorophenyl)porphyrins by an OsO4-mediated dihydroxylation reaction, followed by an intramolecular nucleophilic aromatic substitution reaction, is described. The reaction sequence is applicable to the free base systems as well as their Zn(II), Ni(II), Pd(II), and Pt(II) complexes. The optical properties (UV–vis and fluorescence spectra) of the (metallo)Chlorin-like chromophores that possess slightly red-shifted optical spectra compared to the corresponding 2,3-dihydroxyChlorins are reported. Molecular modeling and 1H–19F-HOESY NMR spectroscopy provide indications for the conformation of the chromene-annulated chromophores. Using 1H–1H COSY and 19F–19F QF-COSY NMR spectra, we interpret the 1H and 19F NMR spectra of the porphyrins and Chlorins, thus providing a refined reference point for the use of 19F NMR spectroscopy as a diagnostic tool in the analysis of meso-pentafluorophenyl-substituted porphyr...
Franz-peter Montforts - One of the best experts on this subject based on the ideXlab platform.
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Functionalization of Chlorins towards potential photosensitizers for photodynamic therapy
Journal of Porphyrins and Phthalocyanines, 2017Co-Authors: Francesc Pont, Franz-peter MontfortsAbstract:Photophysical properties of Chlorins predestine this type of hydroporphyrins for photodynamic therapy and other diagnostic/therapeutic applications. Artificial Chlorins 3a and 4a derived from the red blood pigment heme form a platform for functionalizations with respect towards potentially biologically active photosensitizers and fluorescense markers. Chlorin estrogen derivatives 8a 8b might be useful as sensitizers which bind selectively to (tumor) cell tissue containing estrogen receptors, e.g. breast cancer cells.
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Photoprocesses of Chlorin e6 glucose derivatives
Photochemical & Photobiological Sciences, 2012Co-Authors: Daniela Bauer, Franz-peter Montforts, Aba Losi, Helmut GörnerAbstract:The ground and excited state processes of Chlorin e6, the monomethyl ester C1, the glucose derivative C2 and the 3-heptylChlorin-glucose C3, were studied in solvents of lower and higher polarity. The excited singlet and lowest triplet states of C1-C3 were characterized by spectroscopic methods for several conditions. The quantum yields of formation of singlet molecular oxygen and the other triplet properties of the three Chlorins and Chlorin e6 are similar, whereas the fluorescence quantum yield decreases on going from C1 to C3. Time-resolved optoacoustic experiments revealed a ca. 30 kJ mol(-1) higher triplet level for C3 with respect to C1/2.
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Synthesis of novel porphyrin and Chlorin phosphonic acids and their immobilization on metal oxides
Journal of Porphyrins and Phthalocyanines, 2011Co-Authors: Martin Erbacher, Franz-peter MontfortsAbstract:In this study an easy and flexible access to porphyrin and Chlorin phosphonic acids is presented. Novel types of phosphonic acid terminated porphyrins and Chlorins were synthesized starting from commercially available red blood pigment hemin chloride. Phosphonic acid groups were linked to the porphyrinoids by amide coupling via appropriate spacer moieties. Self-assembled monolayers of the synthesized phosphonates on mesoporous TiO2 electrodes of approximately 3 μm thickness were formed. Surface concentrations in a range of 1 to 4 × 10-8 mol.cm-2 could be determined by UV-vis spectroscopy.
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Synthesis of Chlorins Extendedby Highly Substituted Double Bonds
Synlett, 2008Co-Authors: Frank Dullweber, Franz-peter MontfortsAbstract:Chlorins with highly substituted exocyclic double bonds extendingthe chromophoric system were synthesized starting from the readilyaccessible oxoChlorin. After sulfurization of the keto functionof oxoChlorin 7 the formed thioketo Chlorin 8 underwent Barton olefination with diazocompounds.
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Synthesis of a peptide-linked Chlorin dyad as a model compound for the photosynthetic reaction centre.
Chemistry (Weinheim an der Bergstrasse Germany), 2007Co-Authors: Thorsten Könekamp, Anna Ruiz, Jörn Duwenhorst, Wolfgang Schmidt, Tobias Borrmann, Wolf-dieter Stohrer, Franz-peter MontfortsAbstract:The enantiomerically pure Chlorins 19 and 21 were synthesised from tripyrrolic nickel complex rac-17 and pyrrole building blocks 12 and 16. The pyrroles are annelated with norbornane moieties which contain the chiral information as well as two different functionalities. The functional groups, namely a carboxylic acid ester and a carbonitrile group, of Chlorin 21 finally allowed the formation of an amino acid functionality at the periphery of the macrotetracycle. By using principles of peptide chemistry, the two Chlorin subunits were joined to form the peptide-linked Chlorin-Chlorin dyad 24, which mimics the molecular parts of the natural photosynthetic reaction centre.