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Hitoshi Tamiaki - One of the best experts on this subject based on the ideXlab platform.
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self aggregation of synthetic zinc chlorophyll derivatives possessing 31 hydroxy or methoxy group and 131 mono or dicyanomethylene moiety in nonpolar organic solvents as models of chlorosomal bacteriochlorophyll d aggregates
Photochemistry and Photobiology, 2014Co-Authors: Hitoshi Tamiaki, Masaki Kuno, Masaki OhataAbstract:Methyl 13(1)-(di)cyanomethylene-pyropheophorbides were synthesized by Knoevenagel reactions of the corresponding 13(1)-oxo-Chlorins prepared from modifying chlorophyll-a with malononitrile or cyanoacetic acid. Alternatively, methyl 13(1)-cyanomethylene-pyropheophorbides were produced by Wittig reactions of 13(1)-oxo-Chlorins with Ph3P=CHCN. Self-aggregation of zinc complexes of the semi-synthetic chlorophyll derivatives possessing a hydroxy or methoxy group at the 3(1)-position was examined in 1%(v/v) tetrahydrofuran or dichloromethane and hexane by electronic absorption and circular dichroism spectroscopy. Although intermolecular hydrogen-bonding between the 3(1)-hydroxy and 13(1)-oxo groups of bacteriochlorophylls-c/d/e/f was essential for their self-aggregation in natural light-harvesting antenna systems (=chlorosomes), zinc 3(1)-hydroxy-13(1)-di/monocyanomethylene-Chlorins self-aggregated in the less/lesser polar organic solvents to form chlorosome-like large oligomers in spite of lacking the 13(1)-oxo moiety as the hydrogen-bonding acceptor. Zinc 3(1)-methoxy-13(1)-dicyanomethylene-chlorin gave similar self-aggregates regardless of lack of both the 3(1)-hydroxy and 13(1)-oxo groups. The present self-aggregation was ascribable to stronger coordination of the 3(1)-oxygen atom to the central zinc than the conventional systems, where the electron-withdrawing cyano group(s) increased the coordinative ability of the central zinc through the chlorin π-system.
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Demetalation kinetics of the zinc chlorophyll derivative possessing two formyl groups: effects of formyl groups conjugated to the chlorin macrocycle on physicochemical properties of photosynthetic pigments
Journal of Porphyrins and Phthalocyanines, 2013Co-Authors: Kana Sadaoka, Hitoshi Tamiaki, Shigenori Kashimura, Toru Oba, Yoshitaka SagaAbstract:Demetalation kinetics of zinc chlorophyll derivative 1 possessing two formyl groups directly linked to the A- and B-rings of the chlorin macrocycle, which was synthesized from chlorophyll b, was examined under acidic conditions and compared with those of Zn Chlorins 2 and 3 possessing a single formyl group in the A- and B-ring, respectively, as well as Zn chlorin 4 lacking any formyl group to unravel the substitution effects on demetalation properties of chlorophyllous pigments. Demetalation kinetics of diformylated Zn chlorin 1 was slower than those of monoformylated Zn Chlorins 2 and 3, indicating that the effect of the electron-withdrawing formyl group on demetalation kinetics was amplified by introduction of two formyl groups to the chlorin macrocycle. High correlations were observed between demetalation rate constants of Zn Chlorins 1–4 and the sum of Hammett σ parameters of the 3- and 7-substituents on the chlorin macrocycle, indicating that the combination of electron-withdrawing abilities of the substituents linked directly to the cyclic tetrapyrrole was responsible for demetalation properties of zinc chlorophyll derivatives.
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chlorophyll a derivatives with various hydrocarbon ester groups for efficient dye sensitized solar cells static and ultrafast evaluations on electron injection and charge collection processes
Langmuir, 2010Co-Authors: Xiao-feng Wang, Hitoshi Tamiaki, Li Wang, Naoto Tamai, Osamu Kitao, Haoshen Zhou, Shin-ichi SasakiAbstract:Five chlorophyll-a derivatives, Chlorins-1−5 possessing C32-carboxy and O174-esterified hydrocarbon groups including methyl, hexyl, dodecyl, 2-butyloctyl, and cholesteryl were synthesized. Their performance as sensitizers in dye-sensitized solar cells (DSSCs) was compared. These sensitizers have similar surface coverage on the unit surface of TiO2 film and their absorption spectra on transparent TiO2 films were identical. On the basis of DFT and TD-DFT calculations of these sensitizers in ethanol, a major difference between them was the geometry of the hydrocarbon ester group, to affect their electron injection and charge recombination with the TiO2 electrode rather than the energy level of their molecular orbitals. DSSC based on chlorin-3 with a dodecyl ester group gave a solar energy-to-electricity conversion efficiency of 8%, which was the highest among all the chlorophyllous sensitizers. The large photocurrent in the chlorin-3 sensitized solar cell can be explained by the least impedance in the electr...
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Cyclic tetrapyrrole based molecules for dye-sensitized solar cells
Energy Environ. Sci., 2010Co-Authors: Xiao-feng Wang, Hitoshi TamiakiAbstract:In this Perspective, recent progress on dye-sensitized solar cells (DSSCs) based on cyclic tetrapyrrole type sensitizers including porphyrins, (bacterio)Chlorins, and phthalocyanines has been reviewed. Cyclic tetrapyrrole type molecules have been studied extensively with respect to their photochemical and photophysical properties as well as to various applications. The photophysical properties of tetrapyrrole molecules can be readily controlled upon molecularly structural modification. Their low-lying singlet states are also suitable for studying excited state dynamics in the electron donor–acceptor systems. Here, we selected the most representative porphyrin, (bacterio)chlorin, and phthalocyanine sensitizers to discuss how those structural modifications on the cyclic tetrapyrrole rings affect the performance of DSSCs. The most important factors that strictly determine the power conversion efficiencies of DSSCs based on tetrapyrrole type sensitizers are also discussed in detail.
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synthesis of 3 8 carbonylated chlorophyll derivatives and regiodependent reductivity of their carbonyl substituents
Tetrahedron, 2008Co-Authors: Hitoshi Tamiaki, Kazunori Hamada, Michio KuniedaAbstract:Abstract Methyl pyropheophorbide-d possessing a formyl group at the 3-position and its regioisomer having 8-CHO were prepared and their reactivities with a reductant were determined by the 1H NMR technique: 3-CHO>8-CHO. The regioselective reduction of a synthetic 3,8-diformyl-chlorin also supported the higher reactivity in 3-CHO than in 8-CHO. Regiodependent reduction of the corresponding acetyl-Chlorins confirmed that carbonyl groups at the 3-position in chlorophyllous pigments were reduced more rapidly than those at the 8-position. From the reports that reactions of 3-CHO with amines were preferable to those of 7-CHO, the C O functional groups on the pyrrole A-ring of chlorophylls are more reactive than those on the B-ring.
Jonathan S Lindsey - One of the best experts on this subject based on the ideXlab platform.
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bioconjugatable synthetic Chlorins rendered water soluble with three peg 12 groups via click chemistry
Journal of Porphyrins and Phthalocyanines, 2020Co-Authors: Nobuyuki Matsumoto, Masahiko Taniguchi, Jonathan S LindseyAbstract:Chlorins provide many ideal features for use as red-region fluorophores but require molecular tailoring for solubilization in aqueous solution. A chlorin building-block bearing 18,18-dimethyl, 15-b...
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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 comparisons of pegylated porphyrins Chlorins and bacterioChlorins in water
New Journal of Chemistry, 2016Co-Authors: Amit Kumar Mandal, Jonathan S Lindsey, David F. Bocian, Mengran Liu, Tuba Sahin, Dewey HoltenAbstract:Comparison of the photophysics of analogous members of the porphyrin, chlorin, and bacteriochlorin family has rarely been carried out, and most studies of individual members have been performed in non-aqueous media. Advances in synthesis and molecular design now enable such comparative studies in aqueous solution. A water-soluble bioconjugatable free base porphyrin (FbP1) has been synthesized, complementing recently prepared chlorin and bacteriochlorin analogues. The porphyrin (a trans-AB architecture; i.e., 5,15-substitution pattern) is equipped with one meso-aryl group that bears three short polyethylene glycol (PEG) substituents at the 2,4,6-positions for aqueous solubility, and one meso-aryl group that bears an oxyacetic acid group at the p-position for bioconjugation. Spectroscopic examination of porphyrin FbP1 gave the following quantum yields in DMF versus water: fluorescence (Φf = 0.077 vs. 0.066), intersystem crossing (Φisc = 0.90 vs. 0.84), and internal conversion (Φic = 0.023 vs. 0.094). The increase in Φic upon moving from DMF into water reflects the 4-fold increase in rate constant for internal conversion, from (600 ns)−1 to (140 ns)−1. Photophysical comparisons (τS, kf, kic, kisc, Φf, Φic, Φisc) were made with analogous Chlorins and bacterioChlorins in DMF and water. The value of kic in both media increases in the order (visible-absorbing) porphyrin < (red-absorbing) chlorin < (near-infrared-absorbing) bacteriochlorin, consistent with the general S1-energy dependence of kic expected on the basis of the energy-gap law for non-radiative decay. In summary, there are now satisfactory molecular designs, viable synthetic routes, and thoroughly characterized photophysical properties that permit aqueous solution studies of a complement of porphyrins, Chlorins, and bacterioChlorins.
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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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synthesis and photophysical properties of Chlorins bearing 0 4 distinct meso substituents
Photochemical and Photobiological Sciences, 2013Co-Authors: Kunche Aravindu, James R. Diers, David F. Bocian, Dewey Holten, Masahiko Taniguchi, Hanje Kim, Preston L Dilbeck, Jonathan S LindseyAbstract:The presence of substituents at designated sites about the chlorin macrocycle can alter the spectral properties, a phenomenon that can be probed through synthesis. Prior syntheses have provided access to Chlorins bearing distinct aryl substituents (individually or collectively) at the 5, 10, and 15-positions, but not the 20-position. A new Western half (5-phenyl-2,3,4,5-tetrahydro-1,3,3-trimethyldipyrrin) has been employed in condensation with an Eastern half (9-bromodipyrromethane-1-carboxaldehyde) followed by oxidative cyclization to give (5% yield) the zinc(II) 20-phenylchlorin. Condensation of the same Western half and a diaryl-substituted Eastern half provided (11% yield) the zinc(II) 5,10,20-triarylchlorin; demetalation with TFA followed by 15-bromination and Suzuki coupling gave the free base 5,10,15,20-tetraarylchlorin. Altogether, 10 new synthetic Chlorins have been prepared. The near-UV (B) absorption band of the free base Chlorins shifts bathochromically from 389 to 429 nm and that for the zinc Chlorins from 398 to 420 nm as the number of meso-aryl rings is increased stepwise from 0–4. The long-wavelength (Qy) absorption band undergoes a bathochromic and hypochromic shift upon increase in number of meso-aryl groups. Regardless of the number and positions of the meso-aryl substituents (including “walking a phenyl group around the ring”), the respective fluorescence quantum yields (0.17 to 0.27) and singlet excited-state lifetimes (9.4 to 13.1 ns) are comparable among the free base Chlorins and the same is true for the zinc chelates (0.057 to 0.080; 1.2 to 1.6 ns). Density functional theory calculations show that of the frontier molecular orbitals of the chlorin, the energy of the HOMO−1 is the most affected by meso-aryl substituents, undergoing progressive destabilization as the number of meso-aryl groups is increased. The availability of Chlorins with 0–4 distinct meso-aryl substituents provides the individual stepping-stones to bridge the known unsubstituted chlorin and the meso-tetraarylChlorins.
Michio Kunieda - One of the best experts on this subject based on the ideXlab platform.
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synthesis of 3 8 carbonylated chlorophyll derivatives and regiodependent reductivity of their carbonyl substituents
Tetrahedron, 2008Co-Authors: Hitoshi Tamiaki, Kazunori Hamada, Michio KuniedaAbstract:Abstract Methyl pyropheophorbide-d possessing a formyl group at the 3-position and its regioisomer having 8-CHO were prepared and their reactivities with a reductant were determined by the 1H NMR technique: 3-CHO>8-CHO. The regioselective reduction of a synthetic 3,8-diformyl-chlorin also supported the higher reactivity in 3-CHO than in 8-CHO. Regiodependent reduction of the corresponding acetyl-Chlorins confirmed that carbonyl groups at the 3-position in chlorophyllous pigments were reduced more rapidly than those at the 8-position. From the reports that reactions of 3-CHO with amines were preferable to those of 7-CHO, the C O functional groups on the pyrrole A-ring of chlorophylls are more reactive than those on the B-ring.
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regioisomerically controlled self aggregation of zinc 3 hydroxymethyl 13 formyl chlorin porphyrin and their 3 13 inverted pigments
Journal of Organic Chemistry, 2007Co-Authors: Michio Kunieda, Hitoshi TamiakiAbstract:Zinc 3-hydroxymethyl-13-formyl-chlorin, 1, and its 3,13-inverted (3-formyl-13-hydroxymethyl) regioisomer, 2, and their corresponding 17,18-dehydrogenated porphyrins, 3 and 4, were synthesized for models of natural bacteriochlorophylls-c/d/e possessing 31-OH and 13-CO groups which self-aggregate in main light-harvesting antenna systems of green photosynthetic bacteria. Zinc Chlorins 1 and 2 were monomers in neat THF and gave an obvious difference in their visible absorption spectra, indicating that sole inversion of the 3- and 13-substituents in a chlorin chromophore controlled their optical properties. In an aqueous Triton X-100 solution (a nonionic surfactant), zinc 31-OH-13-CHO-chlorin 1 and porphyrin 3 self-aggregated as do natural bacteriochlorophylls, while zinc 3-CHO-131-OH chlorin 2 and porphyrin 4 (the 3,13-inverted regioisomers of 1 and 3) hardly formed such large oligomers, showing that the inversion of the peripheral 3,13-substituents made their oligomerization unfavorable. FT-IR spectra of agg...
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regioisomerically controlled self aggregation of zinc 3 hydroxymethyl 13 formyl chlorin porphyrin and their 3 13 inverted pigments
Journal of Organic Chemistry, 2007Co-Authors: Michio Kunieda, Hitoshi TamiakiAbstract:Zinc 3-hydroxymethyl-13-formyl-chlorin, 1, and its 3,13-inverted (3-formyl-13-hydroxymethyl) regioisomer, 2, and their corresponding 17,18-dehydrogenated porphyrins, 3 and 4, were synthesized for models of natural bacteriochlorophylls-c/d/e possessing 3(1)-OH and 13-C=O groups which self-aggregate in main light-harvesting antenna systems of green photosynthetic bacteria. Zinc Chlorins 1 and 2 were monomers in neat THF and gave an obvious difference in their visible absorption spectra, indicating that sole inversion of the 3- and 13-substituents in a chlorin chromophore controlled their optical properties. In an aqueous Triton X-100 solution (a nonionic surfactant), zinc 3(1)-OH-13-CHO-chlorin 1 and porphyrin 3 self-aggregated as do natural bacteriochlorophylls, while zinc 3-CHO-13(1)-OH chlorin 2 and porphyrin 4 (the 3,13-inverted regioisomers of 1 and 3) hardly formed such large oligomers, showing that the inversion of the peripheral 3,13-substituents made their oligomerization unfavorable. FT-IR spectra of aggregated 1-4 in the solid film and their molecular modeling calculations suggested that the 17(2)-C=O moiety in inverted 2/4 interacted with its own 13(1)-OH group to disturb further aggregation.
Masahiko Taniguchi - One of the best experts on this subject based on the ideXlab platform.
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bioconjugatable synthetic Chlorins rendered water soluble with three peg 12 groups via click chemistry
Journal of Porphyrins and Phthalocyanines, 2020Co-Authors: Nobuyuki Matsumoto, Masahiko Taniguchi, Jonathan S LindseyAbstract:Chlorins provide many ideal features for use as red-region fluorophores but require molecular tailoring for solubilization in aqueous solution. A chlorin building-block bearing 18,18-dimethyl, 15-b...
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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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Progress Towards Synthetic Chlorins with Graded Polarity, Conjugatable Substituents, and Wavelength Tunability.
Journal of porphyrins and phthalocyanines, 2015Co-Authors: Kelly A. Gauger, Masahiko Taniguchi, Kannan Muthukumaran, Thiagarajan Balasubramanian, Vanampally Chandrashaker, Daniel C. Talley, Melanie A. Ehudin, Marcin PtaszekAbstract: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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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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synthesis and photophysical properties of Chlorins bearing 0 4 distinct meso substituents
Photochemical and Photobiological Sciences, 2013Co-Authors: Kunche Aravindu, James R. Diers, David F. Bocian, Dewey Holten, Masahiko Taniguchi, Hanje Kim, Preston L Dilbeck, Jonathan S LindseyAbstract:The presence of substituents at designated sites about the chlorin macrocycle can alter the spectral properties, a phenomenon that can be probed through synthesis. Prior syntheses have provided access to Chlorins bearing distinct aryl substituents (individually or collectively) at the 5, 10, and 15-positions, but not the 20-position. A new Western half (5-phenyl-2,3,4,5-tetrahydro-1,3,3-trimethyldipyrrin) has been employed in condensation with an Eastern half (9-bromodipyrromethane-1-carboxaldehyde) followed by oxidative cyclization to give (5% yield) the zinc(II) 20-phenylchlorin. Condensation of the same Western half and a diaryl-substituted Eastern half provided (11% yield) the zinc(II) 5,10,20-triarylchlorin; demetalation with TFA followed by 15-bromination and Suzuki coupling gave the free base 5,10,15,20-tetraarylchlorin. Altogether, 10 new synthetic Chlorins have been prepared. The near-UV (B) absorption band of the free base Chlorins shifts bathochromically from 389 to 429 nm and that for the zinc Chlorins from 398 to 420 nm as the number of meso-aryl rings is increased stepwise from 0–4. The long-wavelength (Qy) absorption band undergoes a bathochromic and hypochromic shift upon increase in number of meso-aryl groups. Regardless of the number and positions of the meso-aryl substituents (including “walking a phenyl group around the ring”), the respective fluorescence quantum yields (0.17 to 0.27) and singlet excited-state lifetimes (9.4 to 13.1 ns) are comparable among the free base Chlorins and the same is true for the zinc chelates (0.057 to 0.080; 1.2 to 1.6 ns). Density functional theory calculations show that of the frontier molecular orbitals of the chlorin, the energy of the HOMO−1 is the most affected by meso-aryl substituents, undergoing progressive destabilization as the number of meso-aryl groups is increased. The availability of Chlorins with 0–4 distinct meso-aryl substituents provides the individual stepping-stones to bridge the known unsubstituted chlorin and the meso-tetraarylChlorins.
Tomohiro Miyatake - One of the best experts on this subject based on the ideXlab platform.
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aqueous self aggregates of amphiphilic zinc 31 hydroxy and 31 methoxy Chlorins for supramolecular light harvesting systems
Tetrahedron Letters, 2007Co-Authors: Tomohiro Miyatake, Shuntaro Tanigawa, Syuusaku Kato, Hitoshi TamiakiAbstract:Abstract Aqueous aggregates of zinc 3 1 -hydroxy- and 3 1 -methoxy-13 1 -oxo-Chlorins possessing a hydrophilic tetraoxyethylene chain were prepared. Zinc 3 1 -methoxy-chlorin formed a well-ordered aggregate without intermolecular hydrogen bonding which has been widely accepted in most structural models for BChl- c , d , e aggregates in a major light-harvesting antenna of green photosynthetic bacteria, chlorosome.
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coaggregate of amphiphilic zinc Chlorins with synthetic surfactants in an aqueous medium to an artificial supramolecular light harvesting system
Bioorganic & Medicinal Chemistry, 2004Co-Authors: Tomohiro Miyatake, Hitoshi Tamiaki, Manabu Fujiwara, Takayuki MatsushitaAbstract:Aqueous assemblies of zinc Chlorins possessing a nonionic (oligo)oxyethylene, a cationic quaternary ammonium or an anionic sulfonate group were prepared in the presence of a synthetic surfactant. The nonionic zinc chlorin formed aggregates when admixed with a nonionic surfactant such as Triton X-100 to give a highly ordered oligomeric J-aggregate similarly as natural bacteriochlorophyll-c or d does in a chlorosome. In addition, the coassemblies of the cationic zinc chlorin with an anionic surfactant and of the anionic zinc chlorin with a cationic surfactant gave large oligomers of these chlorophyllous pigments. The structures of hydrophilic groups in both the zinc chlorin and surfactant molecules controlled their aqueous coassemblies.
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synthesis and self assembly of amphiphilic zinc Chlorins possessing a 31 hydroxy group
Tetrahedron, 2002Co-Authors: Tomohiro Miyatake, Hitoshi Tamiaki, Hiroyuki Shinoda, Manabu Fujiwara, Takayuki MatsushitaAbstract:Abstract Amphiphilic zinc Chlorins possessing a 3 1 -hydroxy group were prepared. Non-ionic (oligo)oxyethylene group, anionic sulfonate and cationic quaternary ammonium groups were introduced on the 17-position of a zinc chlorin moiety. All the three kinds of amphiphilic chlorophyll derivatives self-assembled in an aqueous medium to favor a formation of the anti-parallel dimeric structure. In contrast, the amphiphilic zinc Chlorins formed large aggregates in non-polar organic solvent. These studies showed self-assemblies of amphiphilic zinc chlorin chromophores were controlled in environments.
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supramolecular structure of self assembled synthetic zinc 131 oxo Chlorins possessing a primary secondary or tertiary alcoholic 31 hydroxyl group visible spectroscopic and molecular modeling studies
Photochemistry and Photobiology, 2001Co-Authors: Shiki Yagai, Hitoshi Tamiaki, Yoshiyuki Shimono, Tomohiro MiyatakeAbstract:Abstract Zinc-chlorin 3 (see Fig. 2 in text) possessing a tertiary 31-hydroxyl group and a 13-keto group was synthesized as a model for the antenna chlorophylls of green bacteria. Self-aggregation of 3 in nonpolar organic media was examined and compared to 1 and 2 possessing a primary and secondary 31-hydroxyl group, respectively. Zinc-chlorin 3 self-aggregated in 1 vol% CH2Cl2–hexane to form oligomers and showed a red-shifted Qy maximum at 704 nm compared to the monomer (648 nm in CH2Cl2). This red-shift is larger than that of 2S (648 → 697 nm) and comparable to that of 2R (648 → 705 nm), but smaller than that of 1 (648 → 740 nm), indicating that while a single 31-methyl group (prim-OH → sec-OH) suppressed close and/or higher aggregation, the additional 31-methyl group (sec-OH → tert-OH) did not further suppress aggregation. The relative stability of the aggregates was in the order 1 > 2R ∼ 3 > 2S as determined by visible spectral analyses. Molecular modeling calculations on dodecamers of zinc-Chlorins 1...
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self assembly of synthetic zinc Chlorins in aqueous microheterogeneous media to an artificial supramolecular light harvesting device
Helvetica Chimica Acta, 1999Co-Authors: Tomohiro Miyatake, Hitoshi Tamiaki, Alfred R Holzwarth, Kurt SchaffnerAbstract:Self-assembled aggregates of a synthetic zinc chlorin in an aqueous suspension with either α-lecithin or Triton X-100 exhibit unique structural and functional properties. Absorption, circular dichroism, fluorescence, and resonance Raman spectra indicate that the supramolecular structure in an aqueous microheterogeneous medium is very similar to that of the bacteriochlorophyll c aggregates in non-polar organic solvents and in chlorosomes, the main light-harvesting antennae of green photosynthetic bacteria. The nature of the aggregates is controlled by structure and/or concentration of the added surfactants. When a small amount of metal-free bacteriochlorin is present it acts as an efficient energy acceptor from the aggregated zinc Chlorins. Thus, self-assembly of synthetic zinc Chlorins, doped with appropriate energy acceptors and surrounded with surfactants, affords an artificial supramolecular light-harvesting device in aqueous environment.