Papers by Shin-ichi Sasaki
Bioconjugate chemistry, Jan 20, 2018
Native coelenterazine (nCTZ) is a common substrate to most marine luciferases and photoproteins. ... more Native coelenterazine (nCTZ) is a common substrate to most marine luciferases and photoproteins. In this study, nine novel dye- and azide-conjugated CTZ analogues were synthesized by conjugating a series of fluorescent dyes or an azide group to the C-2 or C-6 position of the nCTZ backbone to obtain bulkiness-driven substrate specificity and potential chemiluminescence/bioluminescence resonance energy transfer (C/BRET). The investigation on the optical properties revealed that azide-conjugated CTZs emit greatly biased bioluminescence to ALucs and ca. 130 nm blue-shifted bioluminescence with RLuc8.6 in living animal cells or lysates. The corresponding kinetic study explains that azide-conjugated CTZ exerts higher catalytic efficiency than nCTZ. Nile red-conjugated CTZ completely showed red-shifted CRET spectra and characteristic BRET spectra with artificial luciferase 16 (ALuc16). No or less spectral overlap occurs among [Furimazine-NanoLuc], [6-N-CTZ-ALuc26], [6-pi-OH-CTZ-RLuc8.6], a...
Chemistry (Weinheim an der Bergstrasse, Germany), Jan 3, 2017
Solid-state chlorophyll solar cells (CSCs) employing a carboxylated chlorophyll derivative, methy... more Solid-state chlorophyll solar cells (CSCs) employing a carboxylated chlorophyll derivative, methyl trans-3(2) -carboxypyropheophorbide a, as a light-harvesting dye sensitizer chlorophyll (DSC) deposited on mesoporous TiO2 , on which four zinc hydroxylated chlorophyll derivatives were spin-coated for hole transporter chlorophylls (HTCs), are described. Key parameters, including the effective carrier mobility of the HTC films, as determined by the space charge-limited current method, and the frontier molecular orbitals of these DSCs and HTCs, as estimated from cyclic voltammetry and electronic absorption spectra, suggest that both charge separation and carrier transport are favorable. The power conversion efficiencies (PCEs) of the present CSCs with fluorine-doped tin oxide (FTO)/TiO2 /DSC/HTCs/Ag were determined to follow the order of HTC-1>HTC-2>HTC-3>HTC-4, which coincided perfectly with the order of their hole mobilities. The maximum PCE achieved was 0.86 % with HTC-1. Th...
ChemSusChem, Jan 15, 2016
Chlorophylls (Chls) are abundant, naturally occurring pigments that play key roles in light-harve... more Chlorophylls (Chls) are abundant, naturally occurring pigments that play key roles in light-harvesting and electron/energy transfer in natural photosynthetic apparatus. To demonstrate the idea that Chls are suitable hole transporters, we employed two Chl derivatives, Chl-1 and Chl-2, which self-assembled readily into π-stacking aggregates through a simple spincasting process, in perovskite solar cells (PSCs). The Chl aggregate films exhibit an ultra-smooth film surface, high hole mobility, appropriate energy levels, and efficient hole injection efficiencies that are all key characteristics for efficient hole transporters in PSCs. CH3 NH3 PbI3-x Clx -based PSCs with these Chls as hole transporters were fabricated and compared with P3HT as a standard hole transporter. PSCs based on Chl-1 and Chl-2 without the use of typical additives, such as 4-tert-butylpyridine and lithium bis(trifluoromethanesulfinyl)imide, gave power conversion efficiencies of 11.44 and 8.06 %, respectively. This ...
AIP Conference Proceedings, 2004
Bacteriochlorophyll(=BChl)s- c/d/e are known to be major pigments constructing the main light-har... more Bacteriochlorophyll(=BChl)s- c/d/e are known to be major pigments constructing the main light-harvesting antennae of photosynthetic green bacteria. In this study, methyl bacteriopheophorbide-d derivatives having a series of alkyl or alkenyl substituents at the 8-position and their zinc complexes were synthesized, and their visible absorption spectra and self-aggregation in a solution were examined. It was shown that the C8-substituents conjugating with the chlorin pi-system cause red-shifts of the Qx peaks in their monomeric forms, but do not strongly affect the supramolecular structure of the self-aggregates along the Qy axis. Furthermore, 31-epimerically pure Zn-MBPhe-f analogues possessing the C8-formyl group were also synthesized, and their spectral characteristics were compared to those of the C7-formyl compounds. It was found that the C8-formyl group cause drastic spectral changes both in monomeric and oligomeric forms compared to the spectra of Zn-MBPhe-f having the C7-formyl group. For example, self-aggregates of the former showed more red-shifted Qy peak in 6%THF-H2O than the latter, and larger diastereomeric control in the oligomeric Qy peaks was observed for C8-formyl derivatives than for C7-formyl compounds.
ChemInform, 2010
ABSTRACT ChemInform is a weekly Abstracting Service, delivering concise information at a glance t... more ABSTRACT ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.
Journal of Porphyrins and Phthalocyanines, 2015
A series of chlorophyll derivatives possessing a carboxy group were synthesized aiming at their a... more A series of chlorophyll derivatives possessing a carboxy group were synthesized aiming at their application as sensing materials and to dye-sensitized solar cells (DSSCs). Their absorption and fluorescence responses to amine concentrations in THF and photovoltaic performance of DSSCs on TiO 2 films were investigated.
Journal of the Chemical Society, Perkin Transactions 2, 2001
Expecting a preorganization effect, tripodal anion host molecules were designed and synthesized. ... more Expecting a preorganization effect, tripodal anion host molecules were designed and synthesized. It was demonstrated that two kinds of new thiourea derivatives having a six-fold substituted benzene ring as a preorganized spacer were effective for recognition of the ...
Tetrahedron, 2014
ABSTRACT Chlorophyll derivatives that possessed a phenylsulfanyl group at the C3(1)- or C3(2)-pos... more ABSTRACT Chlorophyll derivatives that possessed a phenylsulfanyl group at the C3(1)- or C3(2)-position were synthesized and their optical properties were investigated. Methyl 3(1)-phenylsulfanyl-mesopyropheophorbide-a was prepared by substitutions of the corresponding C3(1)-hydroxy-chlorin, methyl bacteriopheophorbide-d, with thiophenol in the presence of zinc iodide or of the corresponding C3(1)-bromo-chlorin with thiophenol. The regioisomeric C3(2)-phenylsulfanyl-chlorin was obtained by addition of thiophenol to the C3-vinyl group of methyl pyropheophorbide-a in the presence of AIBN. Both the synthetic compounds gave similar electronic absorption and emission spectra in chloroform, but fluorescence quantum yield of the C3(1)-sulfanyl-chlorin (0.18) was ca. 30% smaller than those of the C3(2)-sulfanyl-chlorin (0.25) and the C3-ethyl-chlorin (0.24). These observations were consistent with their fluorescence lifetime data. It is suggested that the heavy atom effect of a sulfur atom at the C3(1)-position can tune photophysical properties of the chlorophyll derivatives. (C) 2014 Published by Elsevier Ltd.
Tetrahedron, 2013
ABSTRACT Several kinds of cycloaddition reactions were applied to C3-ethynylated pyropheophorbide... more ABSTRACT Several kinds of cycloaddition reactions were applied to C3-ethynylated pyropheophorbide-a methyl ester to develop C3-functionalized chlorophyll derivatives. Its [2+2] cycloaddition with tetracyanoethylene, [2+3] cycloaddition with diazomethane, [2+3] Huisgen reaction with trimethylsilyl azide, and [2+4] Diels-Alder reaction with tetraphenylcyclopentadienone gave the expected products in moderate to high yields. Zinc complex of the resulting 3-pyrazolyl-chlorin was found to show self-aggregation in a less polar solvent, in an aqueous micelle, and in the solid thin films more readily than the corresponding zinc 3-triazolyl-chlorin.
RSC Adv., 2015
In this study, we describe photosynthetic active layers-based photovoltaic cells employing a line... more In this study, we describe photosynthetic active layers-based photovoltaic cells employing a linear carotenoid as the donor and chlorophyll derivatives as the acceptors.
Tetrahedron, 2009
ABSTRACT Zinc complexes of 31-epimerically pure 32,32,32-trifluoro-bacteriopheophorbide-d methyl ... more ABSTRACT Zinc complexes of 31-epimerically pure 32,32,32-trifluoro-bacteriopheophorbide-d methyl ester were prepared and their self-aggregation was examined in 1% (v/v) dichloromethane and hexane by visible and circular dichroism spectroscopies. Both the synthetic 31-trifluoromethylated diastereomers gave amorphous self-aggregates in the nonpolar organic solvent, while the corresponding nonfluorinated compounds possessing the 31-methyl group formed well-ordered and large oligomers similar to in vivo aggregates of bacteriochlorophyll-d in a chlorosome, a main light-harvesting antenna of green photosynthetic bacteria. The difference is ascribed to steric factor of the 3-CF3 group, which was supported by optical properties of other synthetic zinc 31-hydroxy-131-oxo-chlorins possessing trifluoromethyl or secondary/tertiary substituents at the 31-position in the nonpolar organic solvent.
Tetrahedron Letters, 2002
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Journal of the Chemical Society, Perkin Transactions 1, 2001
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ChemInform, 2009
Chlorophyll-and Bacteriochlorophyll-Derived Colorimetric Chemosensors for Amine Detection-[synthe... more Chlorophyll-and Bacteriochlorophyll-Derived Colorimetric Chemosensors for Amine Detection-[synthesis and optical properties of new chemosensors (I) and (II)].
The Journal of Physical Chemistry C, 2009
ABSTRACT Two dye sensitizers, methyl trans-32-carboxy-8-deethyl-7-ethyl-8-oxo-pyropheophorbide-a ... more ABSTRACT Two dye sensitizers, methyl trans-32-carboxy-8-deethyl-7-ethyl-8-oxo-pyropheophorbide-a (BChlorin-1) and methyl trans-32-carboxy-7-demethyl-8-methyl-7-oxo-pyropheophorbide-a (BChlorin-2), with stable bacteriochlorin skeletons were synthesized and applied to dye-sensitized solar cells. Both sensitizers absorb the light all over the visible region owing to partial saturation of the two pyrrole rings on the Qx transition dipole. When they were deposited on a TiO2 film, the J-aggregates of the sensitizers are partially formed to give broad and red-shifted Qy bands. The surface coverage of TiO2 film by BChlorin-2 is much larger than by BChlorin-1, suggesting the former sensitizer forms more serious aggregation on the surface of TiO2, and this could cause more exciton annihilation to reduce the photocurrent of solar cell. The frontier molecular orbitals of both sensitizers obtained from the DFT calculations show no distinguishable difference. Extended calculations on the dye−TiO2Na model system suggest that additional LUMO + 2 orbital in BChlorin-1 may also contribute to the difference in photocurrent. The larger photovoltage in BChlorin-1 sensitized solar cell was attributed to a less efficient charge recombination in the dye−TiO2 interface to give a longer electron lifetime (τ). Additional 4-tert-butylpyridine in the electrolyte significantly reduced the photocurrent and the solar energy-to-electricity conversion efficiency (η) of the solar cells, especially when BChlorin-2 was employed as a sensitizer. This dramatic decrease was attributed to the shift of conduction band edge (CBE) of TiO2 to a negative potential above the molecular Fermi level (MFL) of the sensitizers and suppressed the electron injection from the MFL of sensitizer to CBE of TiO2. Coadsorption of BChlorin-1 with chenodeoxycholic acid (CDCA) could break the dye aggregate and improve the incident photon-to-current conversion efficiency at the absorption bands maxima. BChlorin-1 sensitized solar cells coadsorbed with CDCA gave a longer electron lifetime and a larger diffusion coefficient than the cell without CDCA. By coadsorbing with 5 mM CDCA in solution, the BChlorin-1 sensitized solar cell gave a highest performance with short-circuit photocurrent = 18.4 mA cm−2, open-circuit photovoltage = 0.54 V, fill factor = 0.66, and η = 6.6% under the air mass AM 1.5 (100 mW cm−2) illumination.
The Journal of Physical Chemistry C, 2008
To a solution of methyl 3-devinyl-3-ethyl-8-deethyl-8-formyl-pyropheophorbide a (110 mg, 0.20 mmo... more To a solution of methyl 3-devinyl-3-ethyl-8-deethyl-8-formyl-pyropheophorbide a (110 mg, 0.20 mmol) in THF (15 mL) and 2-methyl-2-butene (8 mL) added was a solution of NH 2 SO 3 H (120 mg, 1.2 mmol) in H 2 O (1.5 mL), and the mixture was stirred for 5 min at room temperature. NaClO 2 (100 mg, 1.1 mmol) in H 2 O (1 mL) was added dropwise and the disappearance of 8-formyl-chlorin was checked by TLC. The mixture was poured into H 2 O, extracted with CH 2 Cl 2 , and concentrated in vacuo. The product was purified by silica-gel chromatography (MeOH-CH 2 Cl 2 , 1:9) followed by GPC column
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Papers by Shin-ichi Sasaki