Kyushu University · Biochemistry, Genetics and Molecular Biology
Professor Hisashi Shimakoshi's research lab specializes in the development of bio-inspired and hybrid photocatalytic systems for environmental remediation and sustainable molecular transformations. The lab focuses on designing cobalamin (vitamin B12)-based catalysts and their integration with semiconductors like TiO2 or transition metal complexes to enable efficient dechlorination of persistent organic pollutants under mild conditions, including visible or UV light irradiation. Key research directions include the mechanistic study of C–X bond cleavage, the stabilization of reactive intermediates such as cobalt–carbon bonds, and the application of these systems in selective esterification and dehalogenation reactions. The lab also explores electrochemical and photoelectrochemical processes for the transformation of toxic halogenated compounds, emphasizing catalyst recovery and reusability.
Figures are computed from collected data and may differ slightly.
An oxygen switch in catalysis of the cobalamin derivative (B12 )-TiO2 hybrid catalyst for the dechlorination of trichlorinated organic compounds has been developed. The covalently bound B12 on the TiO2 surface transformed trichlorinated organic compounds into an ester and amide by UV light irradiation under mild conditions (in air at room temperature), while dichlorostilbenes (E and Z forms) were formed in nitrogen from benzotrichloride. A benzoyl chloride was formed as an intermediate of the es
The hybrid polymer was synthesized by a radical polymerization of a B(12) derivative and a Ru complex having styrene moieties in each peripheral position, and the hybrid polymer showed photocatalytic activity for molecular transformation with visible light irradiation.
Dechlorination of 1,1-bis(4-chlorophenyl)-2,2,2-trichloroethane (DDT) was catalyzed by a hydrophobic vitamin B(12), heptamethyl cobyrinate perchlorate, with a visible light irradiation system containing a [Ru(ii)(bpy)(3)]Cl(2) photosensitizer, and the hydrophobic vitamin B(12) showed high catalytic efficiency and stability during the reaction.
The controlled-potential electrolysis of 1,1-bis(4-chlorophenyl)-2,2,2-trichloroethane (DDT) was carried out at -1.4 V vs. Ag-AgCl in the presence of a hydrophobic vitamin B12, heptamethyl cobyrinate perchlorate. DDT was dechlorinated to form 1,1-bis(4-chlorophenyl)-2,2-dichloroethane (DDD), 1,1-bis(4-chlorophenyl)-2,2-dichloroethylene (DDE), 1-chloro-2,2-bis(4-chlorophenyl)ethylene (DDMU) and 1,1,4,4-tetrakis(4-chlorophenyl)-2,3-dichloro-2-butene (TTDB)(E/Z), and quantitative recovery of the ca
The electrolysis of benzotrichloride at -0.9 V vs. Ag/AgCl in the presence of the B12 model complex, heptamethyl cobyrinate perchlorate, in ethanol under aerobic conditions using an undivided cell equipped with a platinum mesh cathode and a zinc plate anode produced ethylbenzoate in 56% yield with 92% selectivity. The corresponding esters were obtained when the electrolysis was carried out in various alcohols such as methanol, n-propanol, and i-propanol. Benzoyl chloride was detected by GC-MS du
Abstract A cobalamin derivative, cobyrinic acid, was effectively immobilized on TiO2, and the hybrid TiO2 was characterized by UV–vis, XPS, MALDI-TOFMS as well as TEM analysis. The hybrid TiO2 exhibits high reactivity for dehalogenation of various organic halides such as phenethyl bromide, benzyl bromide, and 1,1-bis(4-chlorophenyl)-2,2,2-trichloroethane (DDT) under irradiation with UV light at room temperature.
The B(12)-TiO(2) hybrid catalyst was effectively used for the radical reactions, such as 1,2-migrations of phenyl groups and acyl groups under irradiation by UV light, and the selectivity of the reaction was controlled by the solvent system.
Photocatalytic syntheses of gem-difluoroolefins were performed using the B<sub>12</sub>-TiO<sub>2</sub> hybrid catalyst during the C[double bond, length as m-dash]C bond reduction of α-trifluoromethyl styrenes with C-F bond cleavage at room temperature under nitrogen. The gem-difluoroolefins were used as synthetic precursors for fluorinated cyclopropanes.
Abstract The B 12 ‐TiO 2 hybrid catalyst mediates H 2 O reduction to form hydrogen under UV irradiation (turnover number of one per hour). The catalyst also mediates reductions of alkenes such as styrene derivatives and alkylacrylates (maximum turnover number of 100 per hour) under mild conditions of room temperature, ordinary pressure, and water or alcohol as solvent.
A heavy atom, bromine, was directly substituted into the porphycene macrocycle to promote intersystem crossing by way of spin-orbit coupling. The singlet oxygen production ability of the porphycene is dramatically enhanced, and the highest value of 0.95 for the quantum yield of singlet oxygen generation (PhiDelta) was obtained for the dibrominated porphycene by visible light excitation.
Visible light-driven cross-coupling reactions of alkyl halides with phenylacetylene and its derivatives catalyzed by the cobalamin derivative (B<sub>12</sub>) with the [Ir(dtbbpy)(ppy)<sub>2</sub>]PF<sub>6</sub> photocatalyst at room temperature are reported.
The reduction pathway of cobalester (CN)Cble, an amphiphilic vitamin B12 derivative, was investigated in organic solvents under electrochemical conditions and compared with mono- and dicyanocobyrinates. The redox characteristics were determined using cyclic voltammetry and spectroelectrochemical methods. The presence of a nucleotide moiety in B12-derivative impedes the in situ formation of dicyano-species thus facilitating the (CN)Co(iii) to Co(i) reduction. The (CN)Cble shows stepwise reduction
This Minireview is focused on the development of hybrid catalysts composed of photosensitizers and a metal complex, especially vitamin B<sub>12</sub> derivatives. The semiconductor-metal complex composites are effective photocatalysts for molecular transformations due to the synergistic effect between the two components. The design of a B<sub>12</sub> complex for the hybridization with TiO<sub>2</sub> was simple and straightforward-cobyrinic acid, having seven carboxylic groups derived from natu
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