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51.
Matsubayashi A Fukunaga K Tsuji T Ataka K Ohsaki H 《Langmuir : the ACS journal of surfaces and colloids》2011,27(2):733-740
Interference light-induced photogeneration of metal nanoparticle in polymer films was explored. The nanoparticle was obtained from metal complex homogeneously dispersed in the film. Standing waves resulting from light interference were generated by irradiating nearly monochromatic light to the sample placed on a reflective substrate. During irradiation metal nanoparticles were developed by photoreduction of the metal complexes forming layers rich with particles. These nanoparticle-enriched layers were found to align in parallel to the reflective substrate, and they were separated from each other by a constant spacing. This layer spacing was varied by changing the wavelength and/or the incident angle of the irradiating light. The observed results show that the spatial distribution of the nanoparticles is determined by the optical interference within the film. Surprisingly, regions exist between the nanoparticle-enriched layers where the metal species are not detected. Such regions extends for distances larger than tens of nanometers. This means that the metal complexes initially homogeneously dispersed within the polymer were transported away from certain regions upon photoirradiation. The metal precursors are preferentially photoreduced into the metal nanoparticles at the constructive interference regions. The spatially varying consumption rates of the precursors are considered to lead a concentration gradient, thereby causing a directional diffusion of the unreduced precursors toward the regions where constructive interference occurs. 相似文献
52.
Binding of Scandium Ions to Metalloporphyrin–Flavin Complexes for Long‐Lived Charge Separation
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Prof. Dr. Takahiko Kojima Ryosuke Kobayashi Dr. Tomoya Ishizuka Shinya Yamakawa Dr. Hiroaki Kotani Dr. Tatsuaki Nakanishi Dr. Kei Ohkubo Dr. Yoshihito Shiota Prof. Dr. Kazunari Yoshizawa Prof. Dr. Shunichi Fukuzumi 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(47):15518-15532
A porphyrin–flavin‐linked dyad and its zinc and palladium complexes (MPor?Fl: 2 ?M, M=2 H, Zn, and Pd) were newly synthesized and the X‐ray crystal structure of 2 ?Pd was determined. The photodynamics of 2 ?M were examined by femto‐ and nanosecond laser flash photolysis measurements. Photoinduced electron transfer (ET) in 2 ?H2 occurred from the singlet excited state of the porphyrin moiety (H2Por) to the flavin (Fl) moiety to produce the singlet charge‐separated (CS) state 1(H2Por.+?Fl.?), which decayed through back ET (BET) to form 3[H2Por]*?Fl with rate constants of 1.2×1010 and 1.2×109 s?1, respectively. Similarly, photoinduced ET in 2 ?Pd afforded the singlet CS state, which decayed through BET to form 3[PdPor]*?Fl with rate constants of 2.1×1011 and 6.0×1010 s?1, respectively. The rate constant of photoinduced ET and BET of 2 ?M were related to the ET and BET driving forces by using the Marcus theory of ET. One and two Sc3+ ions bind to the flavin moiety to form the Fl?Sc3+ and Fl?(Sc3+)2 complexes with binding constants of K1=2.2×105 M ?1 and K2=1.8×103 M ?1, respectively. Other metal ions, such as Y3+, Zn2+, and Mg2+, form only 1:1 complexes with flavin. In contrast to 2 ?M and the 1:1 complexes with metal ions, which afforded the short‐lived singlet CS state, photoinduced ET in 2 ?Pd???Sc3+ complexes afforded the triplet CS state (3[PdPor.+?Fl.??(Sc3+)2]), which exhibited a remarkably long lifetime of τ=110 ms (kBET=9.1 s?1). 相似文献
53.
Shima S Schick M Kahnt J Ataka K Steinbach K Linne U 《Dalton transactions (Cambridge, England : 2003)》2012,41(3):767-771
[Fe]-hydrogenase catalyzes the reversible heterolytic cleavage of H(2) and stereo-specific hydride transfer to the substrate methenyltetrahydromethanopterin in methanogenic archaea. This enzyme contains a unique iron guanylylpyridinol (FeGP) cofactor as a prosthetic group. It has recently been proposed-on the basis of crystal structural analyses of the [Fe]-hydrogenase holoenzyme-that the FeGP cofactor contains an acyl-iron ligation, the first one reported in a biological system. We report here that the cofactor can be reversibly extracted with acids; its exact mass has been determined by electrospray ionization Fourier transform ion cyclotron resonance mass-spectrometry. The measured mass of the intact cofactor and its gas-phase fragments are consistent with the proposed structure. The mass of the light decomposition products of the cofactor support the presence of acyl-iron ligation. Attenuated total reflection infrared spectroscopy of the FeGP cofactor revealed a band near wave number 1700 cm(-1), which was assigned to the C=O (double bond) stretching mode of the acyl-iron ligand. 相似文献