Singlet Fission in Solid 1,6-Diphenyl-1,3,5-hexatriene Dicarboxylic Acids and Esters: Effects of Meta and Para Substitution Yoriko Sonoda; Ryuzi Katoh; Norimitsu Tohnai; Tomoaki Yago; Masanobu Wakasa
JOURNAL OF PHYSICAL CHEMISTRY C,
Volume：126,
Number：20,
First page：8742,
Last page：8751, May 2022
As an exciton multiplication process, singlet fission (SF) can potentially increase the energy conversion efficiency of solar cells and other optoelectronic devices. (E,E,E)-1,6-Diphenyl-1,3,5-hexatriene (DPH) is an air-stable SF-active chromophore having a triplet state of higher energy and longer lifetime compared with those of tetracenes and pentacenes. However, functionalization of DPH molecule by the introduction of substituents has not been fully studied yet. In this work, DPH dicarboxylic acids and esters substituted in the meta and para positions of the phenyl rings were prepared to investigate the effects of position isomerism on energetics, molecular arrangements, and solid-state SF properties. We discovered that all four trienes were SF materials. For both the acid and ester, the meta isomers exhibit faster SF and more efficient triplet diffusion than the para isomers as shown by steady-state and time-resolved fluorescence measurements with and without a magnetic field. Crystallographic analysis reveals that molecules of meta ester are arranged to form slipped-parallel stacks, whereas those of the para ester are stacked in a herringbone fashion. The better SF properties, namely the faster SF and more efficient triplet diffusion, brought about by meta substitution can be attributed to more suitable energetics and more favorable molecular arrangements for SF to occur. We also found that propionic acid DPH (PA-DPH), a commercial fluorescence probe for biomembrane studies, underwent SF in the solid state.
AMER CHEMICAL SOC, English, Scientific journal
DOI：https://doi.org/10.1021/acs.jpcc.2c01474DOI ID：10.1021/acs.jpcc.2c01474,
ISSN：1932-7447,
eISSN：1932-7455,
Web of Science ID：WOS:000820430400001 Low magnetic field effects on a photoinduced electron transfer reaction in an ionic liquid Nanshi Harada; Taisuke Matsuo; Tomoaki Yago; Kiminori Maeda; Masanobu Wakasa
Chemical Physics Letters,
Volume：773,
First page：138569,
Last page：138569, Jun. 2021
Elsevier {BV}, English, Scientific journal
DOI：https://doi.org/10.1016/j.cplett.2021.138569DOI ID：10.1016/j.cplett.2021.138569,
ISSN：0009-2614,
ORCID：106571386 Geminate Delayed Fluorescence by Anisotropic Diffusion-Mediated Reversible Singlet Fission and Triplet Fusion Kazuhiko Seki; Tomomi Yoshida; Tomoaki Yago; Masanobu Wakasa; Ryuzi Katoh
The Journal of Physical Chemistry C,
Volume：125,
Number：6,
First page：3295,
Last page：3304, Feb. 2021
American Chemical Society ({ACS}), Scientific journal
DOI：https://doi.org/10.1021/acs.jpcc.0c10582DOI ID：10.1021/acs.jpcc.0c10582,
ORCID：88196688 Diffusion of Radical Ions in Ionic Liquids Having Long Alkyl Chains Tsuchida, Hikaru; Takeda, Tomoya; Ishii, Yuya; Yago, Tomoaki; Wakasa, Masanobu
The Journal of Physical Chemistry B, 2019
Scientific journal
DOI：https://doi.org/10.1021/ACS.JPCB.9B06007DOI ID：10.1021/ACS.JPCB.9B06007,
ORCID：89742478,
Web of Science ID：WOS:000490354600011 Exploring the Structure of an Exchange-Coupled Triplet Pair Generated by Singlet Fission in Crystalline Diphenylhexatriene: Anisotropic Magnetic Field Effects on Fluorescence in High Fields Ishikawa Kei; Yago Tomoaki; Wakasa Masanobu
JOURNAL OF PHYSICAL CHEMISTRY C,
Volume：122,
Number：39,
First page：22264,
Last page：22272, Oct. 2018,
[Reviewed]DOI：https://doi.org/10.1021/acs.jpcc.8b06026DOI ID：10.1021/acs.jpcc.8b06026,
ISSN：1932-7447,
Web of Science ID：WOS:000446926400005 Structure and dynamics of triplet-exciton pairs generated from singlet fission studied via magnetic field effects
Masanobu Wakasa; Tomoaki Yago; Yoriko Sonoda; Ryuzi Katoh
Communications Chemistry, Volume：1, First page：1, Last page：6, Mar. 2018, [Reviewed]
English, Scientific journal
A spin exchange model for singlet fission Yago Tomoaki; Wakasa Masanobu
CHEMICAL PHYSICS LETTERS,
Volume：695,
First page：240,
Last page：244, Mar. 2018,
[Reviewed]DOI：https://doi.org/10.1016/j.cplett.2018.02.025DOI ID：10.1016/j.cplett.2018.02.025,
ISSN：0009-2614,
Web of Science ID：WOS:000427386500038 Singlet Fission in Fluorinated Diphenylhexatrienes Ryuzi Katoh; Masaaki Hashimoto; Akinori Takahashi; Yoriko Sonoda; Tomoaki Yago; Masanobu Wakasa
JOURNAL OF PHYSICAL CHEMISTRY C,
Volume：121,
Number：46,
First page：25666,
Last page：25671, Nov. 2017,
[Reviewed]Experimentally determined quantum yields, decay profiles, and magnetic field effects on fluorescence showed that fluorinated derivatives of diphenylhexatriene were singlet fission materials. The rate constant of singlet fission was estimated as a function of temperature from the initial rate of decay of the fluorescence profiles. The origin of the temperature dependence was discussed in relation to the molecular stacking structure of the crystals.
AMER CHEMICAL SOC, English, Scientific journal
DOI：https://doi.org/10.1021/acs.jpcc.7b06905DOI ID：10.1021/acs.jpcc.7b06905,
ISSN：1932-7447,
Web of Science ID：WOS:000416496200007 Magnetic Field Effects on Triplet Pair Generated by Singlet Fission in an Organic Crystal: Application of Radical Pair Model to Triplet Pair Tomoaki Yago; Kei Ishikawa; Ryuzi Katoh; Masanobu Wakasa
JOURNAL OF PHYSICAL CHEMISTRY C,
Volume：120,
Number：49,
First page：27858,
Last page：27870, Dec. 2016,
[Reviewed]Magnetic field effects (MFEs) on triplet pairs generated by singlet fission (SF) in an organic crystal, 1,6diphenyl-1,3,5-hexatriene, were studied by steady-state fluorescence measurements under ultrahigh magnetic fields of up to 10 T and by time-resolved fluorescence measurements with subnanosecond time resolution in the presence of magnetic field of 0.5 T. The observed MFEs were analyzed by using the stochastic Liouville equation based on the radical pair model with a modification of the spin Hamiltonian. Excellent agreements between the observed and the simulated MFEs demonstrate that the radical pair model used in the present study can apply to analysis of MFEs on triplet pairs generated by SF in organic materials. Model calculations were performed generated in the triplet pairs. The magnitude of the exchange from the observation of the MFE generated in the triplet pairs. The magnitude of the exchange from the observation of the MFE caused by the level crossing mechanism. We also determined the structure of the correlated triplet pair generated by the SF in 1,6-diphenyl-1,3,5-hexatriene crystal.
AMER CHEMICAL SOC, English, Scientific journal
DOI：https://doi.org/10.1021/acs.jpcc.6b09570DOI ID：10.1021/acs.jpcc.6b09570,
ISSN：1932-7447,
Web of Science ID：WOS:000390072100014 Photocyclization Reactions of Diarylethenes via the Excited Triplet State Murata Ryutaro; Yago Tomoaki; Wakasa Masanobu
JOURNAL OF PHYSICAL CHEMISTRY A,
Volume：119,
Number：45,
First page：11138,
Last page：11145, Nov. 2015,
[Reviewed]DOI：https://doi.org/10.1021/acs.jpca.5b08205DOI ID：10.1021/acs.jpca.5b08205,
ISSN：1089-5639,
Web of Science ID：WOS:000364435300012 What Can Be Learned from Magnetic Field Effects on Singlet Fission:Role of Exchange Interaction in Excited Triplet Pairs Masanobu Wakasa; Mana Kaise; Tomoaki Yago; Ryuzi Katoh; Yusuke Wakikawa; Tadaaki Ikoma
J. Phys. Chem. C,
Volume：119,
First page：25840,
Last page：25844, Oct. 2015,
[Reviewed]English, Scientific journal
DOI：https://doi.org/10.1021/acs.jpcc.5b10176DOI ID：10.1021/acs.jpcc.5b10176 Time-Resolved Detection of Magnetic Field Effects on Radical Pairs in Micelles: Two-Step Two-Laser Fluorescence Spectroscopy of Transient Radicals Yago Tomoaki; Takashino Ayuto; Wakasa Masanobu
JOURNAL OF PHYSICAL CHEMISTRY C,
Volume：119,
Number：34,
First page：20217,
Last page：20223, Aug. 2015,
[Reviewed]DOI：https://doi.org/10.1021/acs.jpcc.5b07524DOI ID：10.1021/acs.jpcc.5b07524,
ISSN：1932-7447,
Web of Science ID：WOS:000360415700078 Erratum: A practical approach to calculate the time evolutions of magnetic field effects on photochemical reactions in nano-structured materials(Phys. Chem. Chem. Phys. (2015) 10.1039/c5cp00595g) Tomoaki Yago; Masanobu Wakasa
Physical Chemistry Chemical Physics,
Volume：17,
Number：18,
First page：12366, May 2015,
[Reviewed]Royal Society of Chemistry, English, Scientific journal
DOI：https://doi.org/10.1039/c5cp90061aDOI ID：10.1039/c5cp90061a,
ISSN：1463-9076,
SCOPUS ID：84928902428 A practical approach to calculate the time evolutions of magnetic field effects on photochemical reactions in nano-structured materials Yago Tomoaki; Wakasa Masanobu
PHYSICAL CHEMISTRY CHEMICAL PHYSICS,
Volume：17,
Number：15,
First page：9737,
Last page：9747, 2015,
[Reviewed]DOI：https://doi.org/10.1039/C5CP00595GDOI ID：10.1039/C5CP00595G,
ISSN：1463-9076,
Web of Science ID：WOS:000352270700017 A practical approach to calculate the time evolutions of magnetic field effects on photochemical reactions in nano-structured materials (vol 17, pg 9737, 2015) Yago Tomoaki; Wakasa Masanobu
PHYSICAL CHEMISTRY CHEMICAL PHYSICS,
Volume：17,
Number：18,
First page：12366, 2015,
[Reviewed]DOI：https://doi.org/10.1039/c5cp90061aDOI ID：10.1039/c5cp90061a,
ISSN：1463-9076,
Web of Science ID：WOS:000353767500049 Diffusion and Solvation of Radical Ions in an Ionic Liquid Studied by the MFE Probe Tomoaki Yago; Yuya Ishii; Masanobu Wakasa
JOURNAL OF PHYSICAL CHEMISTRY C,
Volume：118,
Number：38,
First page：22356,
Last page：22367, Sep. 2014,
[Reviewed]Magnetic field effects (MFEs) on photoinduced electron transfer reaction between benzophenone (BP) and 1,4-diazabicyclo [2.2.2] octane in an ionic liquid (IL) of N,N,N-trimethyl-N-propylammonium bis(trifluoromethanesulfonyl) amide were studied by a nanosecond laser flash photolysis technique. The escape yield of the benzophenone radical anion (BP center dot-) was increased with increasing magnetic field strength (B) of 0 T < B <= 0.1 T and almost saturated at 0.1 T < B <= 1.7 T. The observed MFEs were explained by the hyperfine coupling mechanism (HFCM) and the relaxation mechanism (RM). The large MFEs indicate the nanometer-scaled cage effects on the diffusion of the radical ion pairs (RIP) generated by the photoinduced electron transfer reaction in TMPA TFSA. The cage lifetime for the RIP was estimated to be 170 ns, which is much longer than that previously reported for the neutral radical pairs (<20 ns) in the same IL. In addition to the large MFEs due to the HFCM and the RM, we also observed the MFE caused by the level crossing mechanism (LCM). These results suggest that compared with the neutral radicals, the radical ions are rigidly solvated in the IL and the nanometer-scaled charge-ordering structures are created around the radical ions.
AMER CHEMICAL SOC, English, Scientific journal
DOI：https://doi.org/10.1021/jp5069544DOI ID：10.1021/jp5069544,
ISSN：1932-7447,
Web of Science ID：WOS:000342396300069 Local structure of ionic liquids probed by self-quenching of thiobenzophenone Miyuki Tanaka; Tomoaki Yago; Masanobu Wakasa
PHYSICAL CHEMISTRY CHEMICAL PHYSICS,
Volume：15,
Number：3,
First page：787,
Last page：794, 2013,
[Reviewed]Self-quenching of the triplet excited state of thiobenzophenone ((TBP)-T-3*) in molecular solvents, a sodium dodecyl sulfate (SDS) micellar solution, and ionic liquids (ILs) was measured using nanosecond laser flash photolysis. In the molecular solvents and ILs, (TBP)-T-3* single-exponentially decayed, and the decay was accelerated with increasing TBP concentration. Self-quenching rate constants (k(SQ)) obtained in the ILs were smaller than those in the molecular solvents with similar solvent viscosities, indicating that molecular diffusion is inhibited in the ILs. In the SDS micellar solution, the decay of (TBP)-T-3* showed two components. The fast decay component was attributed to self-quenching of (TBP)-T-3* which presents inside micelles containing two or more TBP molecules, while the slow decay component was from deactivation of single (TBP)-T-3*. The decay of (TBP)-T-3* in an IL, N, N, N-trimethyl-N-propylammonium bis(trifluoromethylsulfonyl) amide (TMPA TFSA), had only one decay component, showing that unlike the micelles, the local structure of TMPA TFSA does not have a long lifetime. The cage lifetime of TMPA TFSA was estimated to be between 17 and 20 ns.
ROYAL SOC CHEMISTRY, English, Scientific journal
DOI：https://doi.org/10.1039/c2cp42766dDOI ID：10.1039/c2cp42766d,
ISSN：1463-9076,
Web of Science ID：WOS:000312217200008 Cage lifetimes of ionic liquids as studied by the magnetic field effect probe Tomohide Okada; Tomoaki Yago; Tadashi Takamasu; Masanobu Wakasa
PHYSICAL CHEMISTRY CHEMICAL PHYSICS,
Volume：14,
Number：10,
First page：3490,
Last page：3497, 2012,
[Reviewed]Magnetic field effects (MFEs) on the photoinduced hydrogen abstraction reaction of benzophenone with phenol were investigated in ionic liquids (ILs) with a short alkyl chain (N,N,N-trimethyl-N-propylammonium bis(trifluoromethanesulfonyl) amide (TMPA TFSA)) and long alkyl chains ((N, N, N-trimethyl-N-octylammonium bis(trifluoromethanesulfonyl) amide (TMOA TFSA) and N-decyl-N,N,N-trimethylammonium bis(trifluoromethanesulfonyl) amide (DTMA TFSA)) by a nanosecond laser flash photolysis technique. In each ionic liquid, escaped radical yield of a benzophenone ketyl radical rapidly increased with increasing magnetic field strength (B) of < T o B <= 0.01 T < At 0.01 T < B <= 0.4 T, the escaped radical yield almost saturated in TMPA TFSA or gradually increased in TMOA TFSA and DTMA TFSA. At much higher fields of 0.4 T < B <= 30 T, the yield gradually decreased, resulting in 10-15% decrease at 30 T. The observed MFEs can be explained by the hyperfine coupling and Dg mechanisms together with the relaxation mechanism. On the time profiles of the transient absorption observed for the benzophenone ketyl radical, MFEs were generated in the time range of 0 < t < 0.6 ms. The cage lifetimes of TMOA TFSA and DTMA TFSA were estimated to be at least 120 ns.
ROYAL SOC CHEMISTRY, English, Scientific journal
DOI：https://doi.org/10.1039/c2cp23747dDOI ID：10.1039/c2cp23747d,
ISSN：1463-9076,
eISSN：1463-9084,
Web of Science ID：WOS:000300314100026 Cyclization Reaction of Diarylethene through the Triplet Excited State Ryutaro Murata; Tomoaki Yago; Masanobu Wakasa
BULLETIN OF THE CHEMICAL SOCIETY OF JAPAN,
Volume：84,
Number：12,
First page：1336,
Last page：1338, Dec. 2011,
[Reviewed]Photocyclization reaction of 1,2-bis(2-methyl-3-benzothienyl)perfluorocyclopentene (BT) in methanol was studied by using nanosecond laser flash photolysis at 296 K. When xanthone was used as a triplet sensitizer, the triplet energy transfer occurred efficiently and the closed-ring product of BT was observed.
CHEMICAL SOC JAPAN, English, Scientific journal
DOI：https://doi.org/10.1246/bcsj.20110212DOI ID：10.1246/bcsj.20110212,
ISSN：0009-2673,
eISSN：1348-0634,
Web of Science ID：WOS:000298906900005 Magnetic Field Effects on Photochemical Reactions in Ionic Liquids with Short Alkyl Chains Tomoaki Yago; Atom Hamasaki; Miyuki Tanaka; Tadashi Takamasu; Masanobu Wakasa
JOURNAL OF PHYSICAL CHEMISTRY C,
Volume：115,
Number：43,
First page：21063,
Last page：21071, Nov. 2011,
[Reviewed]Magnetic field effects (MFEs) on the photoinduced hydrogen abstraction reactions of benzophenone and thiobenzophenone from thiophenol were investigated in several ionic liquids with short alkyl chains by a nanosecond laser flash photolysis technique. In each ionic liquid, escaped radical yields of benzophenone and thiobenzophenone ketyl radicals gradually decreased with increasing magnetic field strength. The observed results were analyzed by using the stochastic Liouville equation (SLE), employing a solvent separated radical pair (SSRP) model where the SSRP with a specific radical-radical distance is stable and has a long lifetime. The SLE analysis revealed that the lifetime of the SSRP and the radical rotation in the SSRP states are strongly correlated with the macroviscosity of the ionic liquids.
AMER CHEMICAL SOC, English, Scientific journal
DOI：https://doi.org/10.1021/jp207816tDOI ID：10.1021/jp207816t,
ISSN：1932-7447,
Web of Science ID：WOS:000296172800033 Magnetic Field Effects on Hydrogen Abstraction of Thiobenzophenone as a Probe of Microviscosity Miyuki Tanaka; Tomoaki Yago; Yoshio Sakaguchi; Tadashi Takamasu; Masanobu Wakasa
JOURNAL OF PHYSICAL CHEMISTRY B,
Volume：115,
Number：9,
First page：1936,
Last page：1943, Mar. 2011,
[Reviewed]Hydrogen abstraction reactions of thiobenzophenone with thiophenol in solutions of varying viscosities (eta = 0.29-42.0 cP) were studied by a nanosecond laser flash photolysis under magnetic fields of 0-15.5 T. In alcoholic solutions, the escaped radical yield (Y) of thiobenzophenone ketyl radical showed appreciable magnetic field effects (MFEs). The observed MFEs can be interpreted with the Delta g mechanism through the triplet radical pair. The relative escaped radical yield (R(1.7T) = Y(1.7T)/Y(0T)) decreased with increasing eta at 0 < eta <= 3.33 cP, but then the yield increased with increasing eta at 3.33 cP <eta <= 2.22 cP. At much higher viscosity, 22.2 cP < eta <= 42 cP, R(1.7T) values become 1.0 within experimental errors. Such quenching of MFE was explained by the spin- orbit coupling recombination of close radical pairs associated with high viscosity. The MFEs on the present reaction is extremely sensitive to the solvent viscosity in the vicinity of the radical pairs. Using this probe reaction, microviscosities of sodium dodecyl sulfate (SDS) and Brij35 micellar solutions were estimated.
AMER CHEMICAL SOC, English, Scientific journal
DOI：https://doi.org/10.1021/jp108898aDOI ID：10.1021/jp108898a,
ISSN：1520-6106,
Web of Science ID：WOS:000287833000002 Nanoscale Structure of Ionic Liquid and Diffusion Process as Studied by the MFE Probe Tomoaki Yago; Masanobu Wakasa
JOURNAL OF PHYSICAL CHEMISTRY C,
Volume：115,
Number：6,
First page：2673,
Last page：2678, Feb. 2011,
[Reviewed]Magnetic field effects (MFEs) observed for photoinduced hydrogen abstract reaction between benzophenone and thiophenol, generating phenylthiyl and benzophenone ketyl radicals, in an ionic liquid of N,N,N,-trimethyl-N-propylammonium bis(trifluoromethanesulfonyl)amide (TMPA TFSA) were analyzed by using the stochastic Liouville equation (SLE) with the cage model and the solvent separated radical pair model, respectively. The MFEs observed on the yield of escaped benzophenone ketyl radical in the range of 0 < B <= 2.0 T were explained by the transverse spin relaxation in the radical pair caused by the large anisotropy of the g-value and the slow rotation of phenylthiyl radical in the IL. The calculated MFE was dependent on a rotational correlation time of the radical as well as the mutual diffusion coefficient for the translational diffusion of the radicals. The SLE analysis revealed that the IL has at least two different viscosity regions, causing the nanoscale cage effect on the radical diffusion in the IL.
AMER CHEMICAL SOC, English, Scientific journal
DOI：https://doi.org/10.1021/jp1108762DOI ID：10.1021/jp1108762,
ISSN：1932-7447,
Web of Science ID：WOS:000287065700010 Photochemical primary process of photo-Fries rearrangement reaction of 1-naphthyl acetate as studied by MFE probe Masao Gohdo; Tadashi Takamasu; Masanobu Wakasa
PHYSICAL CHEMISTRY CHEMICAL PHYSICS,
Volume：13,
Number：2,
First page：755,
Last page：761, 2011,
[Reviewed]Photo-Fries rearrangement reactions of 1-naphthyl acetate (NA) in n-hexane and in cyclohexane were studied by the magnetic field effect probe (MFE probe) under magnetic fields (B) of 0 to 7 T. Transient absorptions of the 1-naphthoxyl radical, T-T absorption of NA, and a short-lifetime intermediate (tau = 24 ns) were observed by a nanosecond laser flash photolysis technique. In n-hexane, the yield of escaped 1-naphthoxyl radicals dropped dramatically upon application of a 3 mT field, but then the yield increased with increasing B for 3 mT < B <= 7 T. These observed MFEs can be explained by the hyperfine coupling and the Delta g mechanisms through the singlet radical pair. The fact that MFEs were observed for the present photo-Fries rearrangement reaction indicates the presence of a singlet radical pair intermediate with a lifetime as long as several tens of nanoseconds.
ROYAL SOC CHEMISTRY, English, Scientific journal
DOI：https://doi.org/10.1039/c0cp00077aDOI ID：10.1039/c0cp00077a,
ISSN：1463-9076,
eISSN：1463-9084,
Web of Science ID：WOS:000285390400048 Magnetic Field Effects on Photochemical Reaction in Mesoporous Silicates of MCM-41 under High Magnetic Fields up to 5 T Tomoaki Maeyama; Hiroki Matsui; Tomoaki Yago; Masanobu Wakasa
JOURNAL OF PHYSICAL CHEMISTRY C,
Volume：114,
Number：50,
First page：22190,
Last page：22196, Dec. 2010,
[Reviewed]Magnetic field effects (MFEs) on photoinduced hydrogen abstraction reaction of xanthone with xanthene were investigated in 2-propanol confined in mesoporous silicates of MCM-41 under high magnetic fields up to 5 T. The observed MFEs were explained by the spin relaxation mechanism associated with the cage effects on diffusion of the radical pairs in nanopores of MCM-41. The qualitative analysis using the stochastic Liouville equation revealed that the motions of the radical pairs are not restricted in the one dimension, although the MCM-41 used in the present study has the one-dimensional pore with the diameter of 1.7 or 2.7 nm. The effective viscosities for rotation of the solute molecule in the pores were estimated to be 5-10 cP.
AMER CHEMICAL SOC, English, Scientific journal
DOI：https://doi.org/10.1021/jp107729sDOI ID：10.1021/jp107729s,
ISSN：1932-7447,
Web of Science ID：WOS:000285236800042 Photostability of Water-dispersible CdTe Quantum Dots: Capping Ligands and Oxygen Saim Emin; Alexandre Loukanov; Masanobu Wakasa; Seiichiro Nakabayashi; Yasuko Kaneko
CHEMISTRY LETTERS,
Volume：39,
Number：6,
First page：654,
Last page：656, Jun. 2010,
[Reviewed]Here we report the effect of various capping ligands on the optical properties and photostability of CdTe quantum dots in aqueous solutions. Ligand exchange procedure is used to prepare water dispersive CdTe nanocrystals capped with aminoethane-thiol, 3-mercaptopropionic and dihydrolipoic acids. The dynamics of photoexcited states is examined by transient photoluminescent spectroscopy. Our results demonstrate that the luminescence intensity of water-dispersible CdTe quantum dots is strongly influenced by molecular oxygen under light irradiation.
CHEMICAL SOC JAPAN, English, Scientific journal
DOI：https://doi.org/10.1246/cl.2010.654DOI ID：10.1246/cl.2010.654,
ISSN：0366-7022,
eISSN：1348-0715,
Web of Science ID：WOS:000279446300050 Reexamination of the Photochemical Primary Process of Photo-Fries Rearrangement Reaction as Studied by MFE Probe Masao Gohdo; Masanobu Wakasa
CHEMISTRY LETTERS,
Volume：39,
Number：2,
First page：106,
Last page：107, Feb. 2010,
[Reviewed]A photo-Fries rearrangement reaction of I-naphthyl acetate in n-hexane Was Studied by a nanosecond laser flash photolysis technique under magnetic fields of 0 to 1.65 T. The escaped yield of 1-naphthoxyl radical decreased with increasing magnetic field (B) at 0 < 8 <= 0.005 T, but inversely increased with increasing B at much higher fields of 0.005 T < B <= 1.65 T. Such inverted magnetic field effects (MFEs) can be interpreted with the hyperfine coupling and the Delta g mechanisms through the singlet radical pair. The fact that MFEs are observed for the present photo-Fries rearrangement reaction suggests a singlet radical pair intermediacy with a lifetime as long as several ns.
CHEMICAL SOC JAPAN, English, Scientific journal
DOI：https://doi.org/10.1246/cl.2010.106DOI ID：10.1246/cl.2010.106,
ISSN：0366-7022,
eISSN：1348-0715,
Web of Science ID：WOS:000275524800014 Hydrogen Bonding Effects on the Reorganization Energy for Photoinduced Charge Separation Reaction between Porphyrin and Quinone Studied by Nanosecond Laser Flash Photolysis Tomoaki Yago; Masao Gohdo; Masanobu Wakasa
JOURNAL OF PHYSICAL CHEMISTRY B,
Volume：114,
Number：7,
First page：2476,
Last page：2483, Feb. 2010,
[Reviewed]Alcohol concentration dependences of photoinduced charge separation (CS) reaction of zinc tetraphenylporphyrin (ZnTPP) and duroquinone (DQ) were investigated in benzonitrile by a nanosecond laser flash photolysis technique. The photoinduced CS reaction was accelerated by the addition of alcohols, whereas the addition of acetonitrile caused little effect on the CS reactions. The simple theory was developed to calculate an increase in reorganization energies induced by the hydrogen bonding interactions between DQ and alcohols using the chemical equilibrium constants for the hydrogen bonding complexes through the concerted pathway and the stepwise one. The experimental results were analyzed by using the Marcus equation where we took into account the hydrogen bonding effects on the reorganization energy and the reaction free energy for the CS reaction. The observed alcohol concentration dependence of the CS reaction rates was well explained by the formation of the hydrogen bonding complexes through the concerted pathway, demonstrating the increase in the reorganization energy by the hydrogen bonding interactions.
AMER CHEMICAL SOC, English, Scientific journal
DOI：https://doi.org/10.1021/jp909927wDOI ID：10.1021/jp909927w,
ISSN：1520-6106,
Web of Science ID：WOS:000274578500019 Primary Photochemical Process of Thiobenzophenone as Studied by Laser Flash Photolysis Tanaka Miyuki; Yago Tomoaki; Wakasa Masanobu
CHEMISTRY LETTERS,
Volume：38,
Number：11,
First page：1086,
Last page：1087, Nov. 2009,
[Reviewed]DOI：https://doi.org/10.1246/cl.2009.1086DOI ID：10.1246/cl.2009.1086,
ISSN：0366-7022,
Web of Science ID：WOS:000272854200037 Ethanol Concentration Dependence of Photoinduced Charge Separation Reaction between Zinc Tetraphenylporphyrin and Duroquinone Studied by Laser Flash Photolysis Tomoaki Yago; Masao Gohdo; Masanobu Wakasa
CHEMISTRY LETTERS,
Volume：38,
Number：9,
First page：880,
Last page：881, Sep. 2009,
[Reviewed]Ethanol concentration dependence of photoinduced charge separation between zinc tetraphenylporphyrin (ZnTPP) and duroquinone (DQ) in benzonitrile was studied by nanosecond laser flash photolysis. Acceleration of the photoinduced charge separation reaction rate by hydrogen bonding between DQ anion radical and ethanol was observed. A simple analysis in the framework of the Marcus theory indicated that the observed electron-transfer reaction rate was affected not only by the decrease of the reaction free energy but also an increase of the reorganization energy in the presence of hydrogen bonding.
CHEMICAL SOC JAPAN, English, Scientific journal
DOI：https://doi.org/10.1246/cl.2009.880DOI ID：10.1246/cl.2009.880,
ISSN：0366-7022,
eISSN：1348-0715,
Web of Science ID：WOS:000270590500004 Anoscale Heterogeneous Structure of Ionic Liquid as Revealed by Magnetic Field Effects
Masanobu Wakasa; Tomoaki Yago; Atom Hamasaki
J. Phys. Chem. B, Volume：113, First page：10559–10562, 2009
The magnetic field effects on photochemical reactions in ionic liquids Masanobu Wakasa
JOURNAL OF PHYSICAL CHEMISTRY B,
Volume：111,
Number：32,
First page：9434,
Last page：9436, Aug. 2007,
[Reviewed]The magnetic field effects (MFEs) on photoinduced hydrogen abstraction reactions of benzophenone (BP) with thiophenol (PhSH) in the ionic liquids (ILs) N,N,N-trimethyl-N-propylammonium bis(trifluoromethanesulfonyl) imide (TMPA TFSI), N-methyl-N-propylpyrrolidinium bis(trifluoromethanesulfonyl) imide (P13 TFSI), and N-methyl-N-propylpiperidinium bis(trifluoromethanesulfonyl) imide (PP13 TFSI) were investigated at 296 K by using a nanosecond laser flash photolysis technique under magnetic fields of 0-1.7 T. Large MFEs were observed for the first time in the ILs. In TMPA TFSI, the yield of the benzophenone ketyl radical gradually decreased with increasing magnetic field strength from 0 to 1.7 T, producing a 20% decrease at 1.7 T.
AMER CHEMICAL SOC, English, Scientific journal
DOI：https://doi.org/10.1021/jp074331aDOI ID：10.1021/jp074331a,
ISSN：1520-6106,
Web of Science ID：WOS:000248658200005 Magnetic Field Effects on the Reaction of a Triplet-born Radical PairConsisting of Two Equivalent Sulphur-centre Radicals under Ultrahigh Fields of up to 28 T
Atom Hamasaki; Yoshio Sakaguchi; Kiyoshi Nishizawa; Giyuu Kido; Masanobu Wakasa
Mole. Phys., Volume：104, First page：1765-1771 7, 2006, [Reviewed]
Anomalous Magnetic Field Effects Interpreted by the Relaxation Mechanism under Ultrahigh Fields of up to 28 T
Atom Hamasaki; Kiyoshi Nishizawa; Yoshio Sakaguchi; Toshiyuki Okada; Giyuu Kido; Masanobu Wakasa
Chemistry Letter, Volume：34, First page：1692-1693, 2005, [Reviewed]
Viscosity dependence of the magnetic field effect due to the Delta g mechanism Y Kitahama; M Wakasa; Y Sakaguchi
JOURNAL OF PHYSICAL CHEMISTRY A,
Volume：108,
Number：5,
First page：754,
Last page：757, Feb. 2004,
[Reviewed]We investigated the magnetic field effect on the yields of the escaping radicals formed by the hydrogen abstraction reaction of excited triplet 4-methoxybenzophenone with 4-chlorothiophenol in mixtures of 2-propanol and cyclohexanol. The yields of the escaping radicals decreased with increasing external magnetic field owing to the Deltag mechanism. The relative yield of the escaping radicals to that in the absence of the external magnetic field in 2-propanol was 0.9 at 1.4 T. The magnetic field effects in a nonviscous solution such as 2-propanol were proportional to the square root of the external magnetic field and the solvent viscosity,(Beta)(1/2). However, the deviation from this relationship, the decrease in the exponent, was observed by increasing the solvent viscosity, up to 60 cP. The relative yield in cyclohexanol was 0.88 at 0.8 T and roughly constant up to 1.4 T.
AMER CHEMICAL SOC, English, Scientific journal
DOI：https://doi.org/10.1021/jp030779+DOI ID：10.1021/jp030779+,
ISSN：1089-5639,
Web of Science ID：WOS:000188553000008 Can an external magnetic field affect the thermal reaction of pentafluorobenzyl chloride with n-butyllithium in hexane?
M Wakasa; H Hayashi
CHEMICAL PHYSICS LETTERS, Volume：340, Number：5-6, First page：493, Last page：499, Jun. 2001, [Reviewed]
The magnetic field effects reported in 1973 for the thermal reaction of pentafluorobenzyl chloride with n-butyllithium in hexane were re-examined at 23 +/- 3 degreesC with modern techniques. Using a new reaction apparatus, which has an electromagnet (up to 14.9 kG) in a glove box under argon atmosphere (H2O and O-2 < 1 ppm), we studied the magnetic field effects on the yields of final products of pentafluorophenylpentane and decafluorodiphenylethane in the absence and presence of an external magnetic field of 14.9 kG. No significant magnetic field effect was observed upon the yields of pentafluorophenylpentane and decafluorodiphenylethane under well-controlled conditions with sufficient repetitions. (C) 2001 Elsevier Science B.V. All rights reserved.
ELSEVIER SCIENCE BV, English, Scientific journal
ISSN：0009-2614, Web of Science ID：WOS:000169373800016
Magnetic field effects and spin dynamics of radical reactions in solution
H Hayashi; Y Sakaguchi; M Wakasa
BULLETIN OF THE CHEMICAL SOCIETY OF JAPAN, Volume：74, Number：5, First page：773, Last page：783, May 2001, [Reviewed]
A pulsed magnet which is useful for the research of chemical reactions has recently been constructed by our group. Here, the world record of the maximum magnetic field (30 T) has been attained in this research area. An optical detected X-band ESR apparatus has also been developed by our group. The world's best sensitivity and resolution have been realized in this apparatus. In this account, we review our recent results on new magnetic field effects and spin dynamics obtained with such novel methods as described above for radical reactions at room temperature in solution. In Section 1, typical mechanisms of MFEs on radical pairs such as the Deltag mechanism and the relaxation mechanism are explained as the introduction of this review. In Section 2, the saturation of MFEs due to the Deltag mechanism observed for radical pairs generated from the photoreduction of 4-methoxybenzophenone with benzenethiol in fluid solutions under ultrahigh fields are described. In Section 3, the saturation and reversion of MFEs due to the relaxation mechanism observed for radical pairs generated from the photoreduction of carbonyl and quinone compounds in micellar solutions under ultrahigh fields are reviewed. In Section 4, the first observation of MFEs on the reactions of three-spin systems generated photochemically in solution are introduced. In Section 5, we describe spin dynamics of radical pairs studied with our optically detected ESR apparatus for radical pairs generated from the photoreduction of carbonyl and quinone compounds in micellar solutions.
CHEMICAL SOC JAPAN, English, Scientific journal
ISSN：0009-2673, eISSN：1348-0634, Web of Science ID：WOS:000169365200001
The electron transfer mechanism for the reaction of the tributylstannyl anion with butyl chlorides
T Kugita; H Onoda; M Wakasa
MAIN GROUP METAL CHEMISTRY, Volume：24, Number：9, First page：613, Last page：616, 2001, [Reviewed]
FREUND PUBLISHING HOUSE LTD, English, Scientific journal
ISSN：0334-7575, Web of Science ID：WOS:000171855000007
Studies of photochemical reactions of 7,8-digermabicyclo[2.2.2]octadienes by steady-state and laser flash photolysis techniques K Mochida; T Kayamori; M Wakasa; H Hayashi; MP Egorov
ORGANOMETALLICS,
Volume：19,
Number：17,
First page：3379,
Last page：3386, Aug. 2000,
[Reviewed]The photochemistry of 1,4-diphenyl-2,3-benzo-7,7,8,8-tetraalkyl-7,8-digermabicyclo[2.2.2]octadienes in solution has been studied in detail by steady-state, nanosecond laser flash photolysis, and matrix isolation techniques. Photolysis of 7,8-digermabicyclo[2.2.2]octadienes in solution resulted mainly in the formation of tetraalkyldigermenes and 1,4-diphenylnaphthalene in the triplet excited state. The 7,8-digermabicyclo[2.2.2]octadiene also photochemically isomerized to 1,4-diphenyl-2,3-benzo-6,6,7,7-tetraalky-6,7-digermatricyclo[3.3.0.0]octane as minor product. The reactions of tetraalkyldigermenes with butadienes (2,3-dimethylbuta-1,3-diene and 2-methylbuta-1,3-diene), carbon tetrachloride, and methanol gave the corresponding digermene trapped products: 1,2-digennacyclohex-4-enes, 1,2-dichlorodigermanes together with hexachloroethane, and methoxydigermanes, respectively, in good yields. The transient bands of tetraalkyldigermenes using nanosecond laser flash photolysis appeared at ca. 380 nm. The rate constants for the quenching reactions of the digermene with oxygen, polyhalomethanes, alcohols, 2,3-dimethylbuta-1,3-diene, 1-hexyne, and triethylsilane were also measured under various conditions. The quenching reactions of digermenes with carbon tetrachloride and ethanol (k = similar to 10(7) M-1 s(-1)) are 100 times faster than that with 1,3-butadiene (h = similar to 10(5): M-1 s(-1)). The digermenes were very rapidly quenched with oxygen (h = similar to 10(8) M-1 s(-1)), but very slowly with 1-hexyne and triethylsilane (k < 10(4) M-1 s(-1)) under reaction conditions. The UV absorption bands of tetraalkyldigermenes generated from 7,8-digermabicyclo[2.2.2]octadienes in matrix at 77 K were also observed at 370-380 nm. The mechanism of digermene formation was also discussed.
AMER CHEMICAL SOC, English, Scientific journal
DOI：https://doi.org/10.1021/om000471uDOI ID：10.1021/om000471u,
ISSN：0276-7333,
Web of Science ID：WOS:000088956200019 Reactions of organogermylenes generated by photolysis of 7-germanorbornadienes and cyclohexagermanes with organic halides and trimethyltin chloride
M Adachi; K Mochida; M Wakasa; H Hayashi
MAIN GROUP METAL CHEMISTRY, Volume：22, Number：4, First page：227, Last page：230, Apr. 1999, [Reviewed]
Reactions of organogermylenes, R2Ge: (R=Me and Pr-1), generated by photolysis of 7-germanorbornadienes and cyclohexagermanes with organic halides (R'X) were examined by chemical trapping experiments and CIDNP measurements. The organogermylenes reacted quantitatively with polyhalomethanes (XCCl3, X=Cl, Br) and benzyl bromide to give the corresponding abstraction products together with polyhaloethanes and bibenzyl, respectively. With trimethyltin chloride the organogermylenes afforded effectively the insertion products.
FREUND PUBLISHING HOUSE LTD, English, Scientific journal
ISSN：0334-7575, Web of Science ID：WOS:000079944400004
Laser flash photolysis of phenyl-substituted cyclic oligogermanes
K Mochida; M Adachi; M Wakasa; H Hayash
PHOSPHORUS SULFUR AND SILICON AND THE RELATED ELEMENTS, Volume：151, First page：237, Last page：243, 1999, [Reviewed]
Photochemical reactions of phenyl-substituted cyclic oligogermanes, (Ph2Ge)(n) (n=4-6), were investigated by laser flash photolysis and chemical trapping experiments.
GORDON BREACH SCI PUBL LTD, English, Scientific journal
ISSN：1042-6507, Web of Science ID：WOS:000083740000022
Temperature effect on the kinetics for the reaction of stannyl anion with primary butyl bromide
T Kugita; M Wakasa
PHOSPHORUS SULFUR AND SILICON AND THE RELATED ELEMENTS, Volume：151, First page：271, Last page：276, 1999, [Reviewed]
The decay of the tributylstannyl anion in the presence of primary butyl bromide were measured with a modified stopped-flow apparatus at low temperatures. The investigation for the differences between that decay at 10 degrees C and -60 degrees C revealed the formation of the stannyl radical as the intermediate of this reaction.
GORDON BREACH SCI PUBL LTD, English, Scientific journal
ISSN：1042-6507, Web of Science ID：WOS:000083740000026
Synthesis and photochemical reactions of polystannanesKunio Mochida; Masamichi Hayakawa; Takuya Tsuchikawa; Yasuo Yokoyama; Masanobu Wakasa; Hisaharu Hayashi
Chemistry Letters,
First page：91,
Last page：92, Dec. 1998,
[Reviewed]Several polystannanes were synthesized by the reaction of dichlorostannanes with samarium (II) diiodide and alkali earth metal (Mg, Ca) vapor-solvent cocondensates. Laser flash photolysis of the polystannane involved Sn-Sn bond homolysis to yield mainly polystannyl radicals.
DOI：https://doi.org/10.1246/cl.1998.91DOI ID：10.1246/cl.1998.91,
ISSN：0366-7022,
SCOPUS ID：0032382523 Kinetic studies of reactions of the stannyl anion with primary alkyl halides by a stopped-flow technique
T Kugita; M Wakasa; J Tamura; H Hayashi
INORGANIC CHEMISTRY COMMUNICATIONS, Volume：1, Number：10, First page：386, Last page：388, Oct. 1998, [Reviewed]
The decay of thr tributylstannyl anion in the presence of primary butyl halides was measured directly with a modified stopped-how apparatus for the first time. The resulting rate constants of the stannyl anion were much larger than those calculated as an electron transfer reaction by the Hush-Marcus theory. It is suggested that the stannyl anion reacts with primary halides as a nucleophile rather than as an electron-donor. (C) 1998 Elsevier Science S.A. All rights reserved.
ELSEVIER SCIENCE BV, English, Scientific journal
ISSN：1387-7003, Web of Science ID：WOS:000077404600007
Direct observation of a stannyl radical in the reactions of the tributylstannyl anion with alkyl halides by a stopped-flow technique
M Wakasa; T Kugita
ORGANOMETALLICS, Volume：17, Number：10, First page：1913, Last page：1915, May 1998, [Reviewed]
The reaction intermediate in, reactions of the tributylstannyl anion. with alkyl halides in THF was studied by a stopped-flow technique. The tributylstannyl radical was observed directly in the reactions of sec- and tert-butyl bromides and iodides. Generation of the stannyl radical suggests that electron transfer from the stannyl anion to alkyl halides is taking place.
AMER CHEMICAL SOC, English, Scientific journal
ISSN：0276-7333, Web of Science ID：WOS:000073789900003
Synthesis, photochemical and conducting properties of oligo(digermanylene-phenylene)s and related compounds
K Mochida; S Maeyama; M Wakasa; H Hayashi
POLYHEDRON, Volume：17, Number：22, First page：3963, Last page：3967, 1998, [Reviewed]
Oligo(digermanylene-phenylene)s and related oligomers were prepared by treatment of di-Grignard reagents of the corresponding aryl dibromides with 1,2-dichlorotetramethyldigermane. Upon ultraviolet irradiation of films of oligo(digermanylene-phenylene) and related oligomer in air, the germanium-germanium bond in the oligomer films changed into a digermoxane chain probed by XPS. The laser flash photolysis of the oligo(digermanylene-phenylene) film showed the formation of an oligogermyl radical as a reactive intermediate during photodegradation. Iodine doping of the oligomers showed the conductivities of the order of 10(-4) S cm(-1) (C) 1998 Elsevier Science Ltd. All rights reserved.
PERGAMON-ELSEVIER SCIENCE LTD, English, Scientific journal
ISSN：0277-5387, Web of Science ID：WOS:000077509300017
Photodegradation of thin films of polygermanes
K Mochida; S Nagano; H Kawata; M Wakasa; H Hayashi
JOURNAL OF ORGANOMETALLIC CHEMISTRY, Volume：542, Number：1, First page：75, Last page：79, Sep. 1997, [Reviewed]
Upon ultraviolet irradiation of thin films of linear polygermanes in air, the germanium-germanium bond in thin films of polygermanes changed into digermoxane chains. The laser flash photolysis of the linear polygermane films showed the formation of polygermyl radicals generated by germanium-germanium bond homolysis as reactive intermediates during photodegradation. (C) 1997 Elsevier Science S.A.
ELSEVIER SCIENCE SA LAUSANNE, English, Scientific journal
ISSN：0022-328X, Web of Science ID：WOS:A1997YB36200009
REVERSION OF MAGNETIC-FIELD EFFECTS OBSERVED IN THE REACTION OF A TRIPLET-BORN RADICAL PAIR CONSISTING OF 2 EQUIVALENT SULFUR-CENTERED RADICALS
M WAKASA; H HAYASHI; Y MIKAMI; T TAKADA
JOURNAL OF PHYSICAL CHEMISTRY, Volume：99, Number：35, First page：13181, Last page：13186, Aug. 1995, [Reviewed]
Magnetic field effects (MFEs) on the triplet sensitization of p-aminophenyl disulfide were investigated in a sodium dodecylsulfate (SDS) micellar solution by means of a nanosecond laser flash photolysis technique at high magnetic fields up to 10 T. The yield of the escaped (P-aminophenyl)thiyl radical increased steeply with increasing magnetic field strength (B) from 0 to 1 T, but decreased gradually from 1 to 10 T. At 10 T, the yield of the escaped radical became similar to that at 0 T. The MFEs observed at both low (B less than or equal to 1 T) and high (1 T < B < 10 T) fields were simultaneously quenched by the addition of a paramagnetic Gd3+ ion, Thus, these reverted MFEs were interpreted by the relaxation mechanism through anisotropic hyperfine and Zeeman interactions.
AMER CHEMICAL SOC, English, Scientific journal
ISSN：0022-3654, Web of Science ID：WOS:A1995RR84600022
MAGNETIC-FIELD AND MAGNETIC ISOTOPE EFFECTS UPON REACTIONS OF HEAVY ATOM-CENTERED RADICALS
H HAYASHI; M WAKASA; Y SAKAGUCHI
JOURNAL OF THE CHINESE CHEMICAL SOCIETY, Volume：42, Number：2, First page：343, Last page：352, Apr. 1995, [Reviewed]
We present our recent studies on magnetic field effects (MFEs) observed in reactions of heavy atom-centered radicals such as Si-,P-, Ge-, and Sn-radicals with a ns-laser photolysis technique under magnetic fields of 0 - 10 T. Although the MFES of heavy atom-centered radicals are much smaller than those of C-radicals due to the spin-orbit interaction of heavy atoms, we have found appreciable MFEs in many reactions of such heavy atom-centered radicals. Comparing the MFES of C-radicals with those of heavy atom-centered ones, we have explained the MFEs of heavy atom-centered radicals in terms of the Delta g and relaxation mechanisms. We have found that the separation between the MFES due to the Delta g mechanism and those due to the relaxation one is possible with the enhancement of spin relaxation by the addition of a paramagnetic ion.
We have also tried to enrich magnetic isotopes of heavy atoms with the magnetic isotope effect (MIL), using the reactions which show fairly large MFES. Recently, we have succeeded in enriching Ge-73. This is the heaviest isotope which has so far been enriched with the MIE from samples of natural abundance.
CHINESE CHEM SOC, English, Scientific journal
ISSN：0009-4536, Web of Science ID：WOS:A1995QW39200029
Paramagnetic Quenching of the Inverted magnetic Field Effects Observed in the Photoreduction of Decafluorobenzophenone in a Brij35 Micellar Solution WAKASA Masanobu; IGARASHI Masatoshi; SAKAGUCHI Yoshio; HAYASHI Hisaharu
Chemistry Letters,
Volume：1994,
Number：10,
First page：1941,
Last page：1944, Oct. 1994
The inversion of magnetic field effects (MFEs) observed in the photoreduction of decafluorobenzophenone was studied in the absence and presence of a paramagnetic Gd
3+ ion. The MFEs appearing at both low (B ≤ 2T) and high (2T < B ≤ 10T) fields were simultaneously quenched by the addition of Gd
3+. For the present reaction, it is concluded that the inversion of the MFEs is due to the relaxation mechanism.
The Chemical Society of Japan, English
DOI：https://doi.org/10.1246/cl.1994.1941DOI ID：10.1246/cl.1994.1941,
ISSN：0366-7022,
CiNii Articles ID：10006894740,
CiNii Books ID：AA00603318 MAGNETIC-FIELD EFFECT ON THE DYNAMIC BEHAVIOR OF A RADICAL PAIR INVOLVING AN SN-CENTERED RADICAL
M WAKASA; H HAYASHI
CHEMICAL PHYSICS LETTERS, Volume：229, Number：1-2, First page：122, Last page：126, Oct. 1994, [Reviewed]
The photoreduction of xanthone with triethyltinhydride in a sodium dodecylsulfate solution was investigated with the aid of a time-resolved ESR and a nanosecond laser flash photolysis. Upon irradiation of xanthone with triethyltinhydride, the hydrogen abstraction occurred and the ketyl-type and cyclohexadienyl-type radicals were observed by CIDEP spectra. The escaped xanthone ketyl radical increased with increasing magnetic field strength up to 1.29 T. The observed magnetic filed effects can be interpreted by a combination of the hyperfine coupling and the relaxation mechanisms in the case of a triplet radical pair.
ELSEVIER SCIENCE BV, English, Scientific journal
ISSN：0009-2614, Web of Science ID：WOS:A1994PN34100021
PHOTOCHEMICAL-REACTIONS OF GERMOXANES - GENERATION OF GERMYL AND GERMOXY RADICALS
K MOCHIDA; S MORI; C YOSHIZAWA; S TOKURA; M WAKASA; H HAYASHI
JOURNAL OF ORGANOMETALLIC CHEMISTRY, Volume：471, Number：1-2, First page：47, Last page：52, May 1994, [Reviewed]
Photochemical reactions of phenyl-substituted digermoxanes, (PhnMe3-nGe)2O (n = 1-3), and a cyclic germoxane, (Me2GeO)4, have been investigated by chemical trapping and laser flash-photolysis. On irradiation, phenylated digermoxanes undergo homolysis of the germanium-oxygen bond to give germyl radicals and germoxy radicals. In the presence of nonhalogenated solvents, these germyl radicals and germoxy radicals couple to yield digermanes and digermyl peroxides, respectively. In polyhalomethanes (CCl4, CHCl3, and BrCCl3), germyl radicals are converted to the corresponding halides by abstraction of a halogen atom. Germoxy radicals do not react with polyhalomethanes; they couple to produce digermyl peroxides which decompose to give either a pair of germoxy radicals or germyl radicals and germylperoxy radicals. Photolysis of a cyclic germoxane also results in cleavage of the germanium-oxygen bond.
ELSEVIER SCIENCE SA LAUSANNE, English, Scientific journal
ISSN：0022-328X, Web of Science ID：WOS:A1994NN48700008
PHOTOCHEMICAL-REACTIONS OF 2-(PENTAMETHYLDISILANYL)FURAN AND 2-(PENTAMETHYLDIGERMANYL)FURAN - FORMATION OF A RADICAL PAIR
K MOCHIDA; K KIMIJIMA; M WAKASA; H HAYASHI
JOURNAL OF ORGANOMETALLIC CHEMISTRY, Volume：465, Number：1-2, First page：101, Last page：107, Feb. 1994, [Reviewed]
Photochemical reactions of 2-(pentamethyldisilanyl)furan and 2-(pentamethyldigermanyl)furan have been investigated by chemical trapping experiments and laser flash-photolysis. On irradiation, the furylated catenates of Group 14 elements undergo silicon-silicon sigma bond and germanium-germanium sigma bond homolysis to give a pair of silyl radicals and germyl radicals, respectively. In CCl4, these radicals are converted to the corresponding chlorides by abstraction of a chlorine atom. In nonhalogenated solvents (cyclohexane and other hydrocarbons), the silyl radical pair undergoes a disproportionation to give as main products a monosilane and a silene. The trimethylgermyl radical mainly couples at the ipso-position of the furyl group of the pairing radical to yield the corresponding diradical. This diradical undergoes elimination of a divalent species, dimethylgermylene, with concomitant formation of 2-(trimethylgermyl)furan.
ELSEVIER SCIENCE SA LAUSANNE, English, Scientific journal
ISSN：0022-328X, Web of Science ID：WOS:A1994MV56500008
MAGNETIC-FIELD EFFECTS ON HYDROGEN ABSTRACTION OF TRIPLET BENZOPHENONE WITH THIOPHENOL IN AN SDS MICELLAR SOLUTION
M WAKASA; Y SAKAGUCHI; H HAYASHI
CHEMISTRY LETTERS, Number：1, First page：49, Last page：50, Jan. 1994, [Reviewed]
The photoreduction of benzophenone with thiophenol was studied by a laser flash photolysis under the magnetic fields of 0-10 T. The escape yields of the benzophenone ketyl and phenylthiyl radicals decreased with increasing magnetic field strength. The observed magnetic field effect can be interpreted by the Ag mechanism in the case of a triplet radical pair.
CHEMICAL SOC JAPAN, English, Scientific journal
ISSN：0366-7022, eISSN：1348-0715, Web of Science ID：WOS:A1994MV93200014
Magnetic field effect on the photodecomposition of p-aminophenyl disulfide in a micellar solution Masanobu Wakasa; Yoshio Sakaguchi; Hisaharu Hayashi
Journal of Physical Chemistry,
Volume：97,
Number：9,
First page：1733,
Last page：1735, 1993,
[Reviewed]Upon laser flash photolysis of p-aminophenyl disulfide at room temperature, the radical pair of two p-aminophenylthiyl radicals was found to be generated by direct excitation and triplet sensitization in the magnetic field range 0-1.35 T. Only in the case of triplet sensitization did the yield of the escaped radical increase with increasing magnetic field strength. The yield at 1.35 T was 1.14 ± 0.2 times as large as that at 0 T. This is the first report of a magnetic field effect on a reaction of two sulfur-centered radicals. © 1993 American Chemical Society.
English, Scientific journal
DOI：https://doi.org/10.1021/j100111a003DOI ID：10.1021/j100111a003,
ISSN：0022-3654,
SCOPUS ID：0011888422 PHOTOCHEMICAL-REACTIONS OF ARYL-SUBSTITUTED DIGERMANES THROUGH A PAIR OF ORGANOGERMYL RADICALS
K MOCHIDA; M WAKASA; Y SAKAGUCHI; H HAYASHI
BULLETIN OF THE CHEMICAL SOCIETY OF JAPAN, Volume：64, Number：6, First page：1889, Last page：1895, Jun. 1991, [Reviewed]
The photochemical reactions of aryl-substituted digermanes were investigated by trapping experiments and a laser flash photolysis technique. The photolysis of phenylated digermanes resulted in germanium-germanium bond homolysis to give a pair of two germyl radicals. The germyl radicals abstracted a chlorine atom from carbon tetrachloride to give chlorogermanes. The pair of germyl radicals also underwent ipso-substitution, which was a precursor of the germylenes. The mechanism for the photochemistry of phenylated digermanes is discussed.
CHEMICAL SOC JAPAN, English, Scientific journal
ISSN：0009-2673, eISSN：1348-0634, Web of Science ID：WOS:A1991FT20500027
FLUORESCENCE OF SILYL AND GERMYL KETONES AND THEIR PRIMARY PHOTOCHEMICAL PROCESSES
M WAKASA; K MOCHIDA; Y SAKAGUCHI; J NAKAMURA; H HAYASHI
JOURNAL OF PHYSICAL CHEMISTRY, Volume：95, Number：6, First page：2241, Last page：2246, Mar. 1991, [Reviewed]
Dual fluorescence was observed for several mono- and bis-silyl and -germyl ketones in solution at room temperature. From their fluorescence spectra, excitation spectra, quantum yields, and time profiles, the observed fluorescence was assigned to the S2 (the second lowest excited singlet state) --> S0 (the ground state) one and the S1 (the lowest excited singlet state) --> S0 one. For the employed mono-M ketones (Ph(n)Me3-nMCOPh, M = Si or Ge), their S2 lifetimes in cyclohexane were shorter than 160 ps and their S1 ones lay between 0.8 and 2.5 ns. For bis(triphenylsilyl) ketone in cyclohexane, its S2 lifetime was 160 ps and its S1 one as long as 460 ns. Norrish type I cleavage of these ketones in solution was also studied with time-resolved optical absorption and ESR techniques.
AMER CHEMICAL SOC, English, Scientific journal
ISSN：0022-3654, Web of Science ID：WOS:A1991FD11200027
Magnetic field effects on the dynamic behavior of a radical pair involving a germyl radical Masanobu Wakasa; Yoshio Sakaguchi; Hisaharu Hayashi
Chemical Physics Letters,
Volume：176,
Number：6,
First page：541,
Last page：545, Feb. 1991,
[Reviewed]Photochemical primary process and magnetic field effect of methyltriphenyl germane in a micelle have been investigated with the aid of a nanosecond laser-flash-photolysis technique. The germyl radical generated through triplet state was directly observed. The lifetime of the generated radical pair and the yield of the escaping germyl radical were increased with increasing magnetic field strength from 0 to 1.35 T. The yield at 1.35 T became 1.16 ± 0.02 times that at 0 T. © 1991.
English, Scientific journal
DOI：https://doi.org/10.1016/0009-2614(91)90252-5DOI ID：10.1016/0009-2614(91)90252-5,
ISSN：0009-2614,
SCOPUS ID：44949279481 PHOTOCHEMISTRY OF ARYL-SUBSTITUTED TRIGERMANES - GENERATION AND MECHANISM OF FORMATION OF GERMYLENES
K MOCHIDA; YONEDA, I; M WAKASA
JOURNAL OF ORGANOMETALLIC CHEMISTRY, Volume：399, Number：1-2, First page：53, Last page：62, Dec. 1990, [Reviewed]
ELSEVIER SCIENCE SA LAUSANNE, English, Scientific journal
ISSN：0022-328X, Web of Science ID：WOS:A1990EN04700005
PHOTOCHEMISTRY OF ARYL-SUBSTITUTED TRIGERMANES
M WAKASA; YONEDA, I; K MOCHIDA
JOURNAL OF ORGANOMETALLIC CHEMISTRY, Volume：366, Number：1-2, First page：C1, Last page：C5, Apr. 1989, [Reviewed]
ELSEVIER SCIENCE SA LAUSANNE, English, Scientific journal
ISSN：0022-328X, Web of Science ID：WOS:A1989U388000025
LASER-PHOTOLYSIS STUDY OF PRIMARY PHOTOPHYSICAL AND PHOTOCHEMICAL PROCESSES OF BIS(TRIPHENYLSILYL)KETONE
M WAKASA; N INOUE; K MOCHIDA; Y SAKAGUCHI; H HAYASHI
CHEMICAL PHYSICS LETTERS, Volume：143, Number：3, First page：230, Last page：234, Jan. 1988, [Reviewed]
ELSEVIER SCIENCE BV, English, Scientific journal
ISSN：0009-2614, Web of Science ID：WOS:A1988L800400005
LASER PHOTOLYSIS AND CIDEP STUDIES OF THE FORMATION OF PHENYL-SUBSTITUTED GROUP 4B ELEMENT (SILICON, GERMANIUM, AND TIN)-CENTERED RADICALS IN DIRECT PHOTOEJECTION OF THE GROUP 4B ELEMENT-CENTERED ANIONS
K MOCHIDA; M WAKASA; Y SAKAGUCHI; H HAYASHI
JOURNAL OF THE AMERICAN CHEMICAL SOCIETY, Volume：109, Number：26, First page：7942, Last page：7947, Dec. 1987, [Reviewed]
AMER CHEMICAL SOC, English, Scientific journal
ISSN：0002-7863, Web of Science ID：WOS:A1987L587100002
LASER PHOTOLYSIS STUDY OF GROUP-4B COMPOUNDS CONTAINING GROUP-4B ELEMENTS (GERMANIUM, TIN)-CARBON BONDS
K MOCHIDA; M WAKASA; Y SAKAGUCHI; H HAYASHI
NIPPON KAGAKU KAISHI, Number：7, First page：1171, Last page：1176, Jul. 1987, [Reviewed]
CHEMICAL SOC JAPAN, Japanese, Scientific journal
ISSN：0369-4577, Web of Science ID：WOS:A1987J152500009
DIRECT OBSERVATION OF STANNYL RADICALS BY LASER-PHOTOLYSIS OF CARBON-TIN AND TIN-TIN BONDS
K MOCHIDA; M WAKASA; Y SAKAGUCHI; H HAYASHI
CHEMISTRY LETTERS, Number：10, First page：1793, Last page：1796, Oct. 1986, [Reviewed]
CHEMICAL SOC JAPAN, English, Scientific journal
ISSN：0366-7022, eISSN：1348-0715, Web of Science ID：WOS:A1986E422200042
LASER-PHOTOLYSIS STUDY OF ARYL-SUBSTITUTED SILYL AND STANNYL ANIONS
K MOCHIDA; M WAKASA; Y SAKAGUCHI; H HAYASHI
CHEMISTRY LETTERS, Number：5, First page：773, Last page：776, May 1986, [Reviewed]
CHEMICAL SOC JAPAN, English, Scientific journal
ISSN：0366-7022, eISSN：1348-0715, Web of Science ID：WOS:A1986C525400036
CIDEP STUDY OF THE FORMATION OF ARYL-SUBSTITUTED GERMYL RADICALS IN DIRECT PHOTOEJECTION OF THE GERMYL ANIONS
K MOCHIDA; M WAKASA; H MURAI; YJ IHAYA; Y SAKAGUCHI; H HAYASHI
CHEMISTRY LETTERS, Number：4, First page：513, Last page：514, Apr. 1986, [Reviewed]
CHEMICAL SOC JAPAN, English, Scientific journal
ISSN：0366-7022, eISSN：1348-0715, Web of Science ID：WOS:A1986C049400022
LASER-PHOTOLYSIS STUDY OF ARYL-SUBSTITUTED GERMYL ANIONS
K MOCHIDA; M WAKASA; S ISHIZAKA; M KOTANI; Y SAKAGUCHI; H HAYASHI
CHEMISTRY LETTERS, Number：11, First page：1709, Last page：1710, 1985, [Reviewed]
CHEMICAL SOC JAPAN, English, Scientific journal
ISSN：0366-7022, eISSN：1348-0715, Web of Science ID：WOS:A1985AUX8000031
Magnetic Field Effect on a Radical Pair Reaction as a Probe of Microviscosity Atom Hamasaki; Tomoaki Yago; Masanobu Wakasa
JOURNAL OF PHYSICAL CHEMISTRY B,
Volume：112,
Number：45,
First page：14185,
Last page：14192, Nov. 2008
The magnetic field effects (MFEs), caused by the Delta g mechanism, on the pehotoinduced hydrogen abstraction reaction of benzopheneone with thiophenol were investigated in alcoholic solutions of varying viscosities (eta = 0.55 to 59.2 cP) by a nanosecond laser flash photolysis technique. The escape yield of benzophenone ketyl radicals (Y) gradually decreased with increasing magnetic field strength (B) from 0 to 1.6 T. The relative yield observed at 1.6 T, R(1.6 T) = Y(1.6 T)/Y(0 T), decreased with increasing eta in the range of 0.55 cP <= eta <= 5 cP, and then increased with increasing eta in the range of 5 cP < eta <= 55.3 cP. When eta was higher than 55.3 cP, the R(1.6 T) value became 1.0, and MFEs were completely quenched. The observed eta dependence of the MFEs was analyzed by the stochastic Liouville equation (SLE), in which the effects of spin-orbit coupling by a heavy atom such as sulfur were taken into account. The observed MFEs were reproduced fairly well by the SLE analysis. The diffusion coefficients of the radicals obtained by the SLE were about three times smaller than those expected from the macroscopic solvent viscosities. One can probe the microviscosity in the vicinity of the radical pairs by observing MFEs on the present photochemical reaction system.
AMER CHEMICAL SOC, English
DOI：https://doi.org/10.1021/jp804862wDOI ID：10.1021/jp804862w,
ISSN：1520-6106,
CiNii Articles ID：80019963904,
PubMed ID：18939791,
Web of Science ID：WOS:000260675800013 Magnetic field effects due to the relaxation mechanism observed for the photo-induced electron transfer reaction of zinc(II) tetraphenylporphyrin and 2-methyl-1,4-naphthoquinone Masao Gohdo; Yasutaka Kitahama; Yoshio Sakaguchi; Masanobu Wakasa
JOURNAL OF PHOTOCHEMISTRY AND PHOTOBIOLOGY A-CHEMISTRY,
Volume：199,
Number：2-3,
First page：130,
Last page：135, Sep. 2008
The magnetic field effects (MFEs) on the photo-induced electron transfer (PET) reaction of zinc(II) tetraphenylporphyrin (ZnTPP) with 2-methyl-1,4-naphthoquinone (2MNQ) in a mixed solvent of cyclohexanol and 2-propanol were investigated at 293 K by a nanosecond laser flash photolysis technique. Upon irradiation of ZnTPP, the electron transfer from ZnTPP to 2MNQ occurred and the corresponding cation and anion radicals were generated. The relative yield of the escaped 2MNQ anion radical, R(B), showed appreciable MFEs. The R(B) values increased between 0 and 0.1 T, then decreased again between 0.1 and 1.65T. The observed MFEs can be explained in terms of the relaxation mechanism. (C) 2008 Elsevier B.V. All rights reserved.
ELSEVIER SCIENCE SA, English
DOI：https://doi.org/10.1016/j.jphotochem.2008.05.006DOI ID：10.1016/j.jphotochem.2008.05.006,
ISSN：1010-6030,
CiNii Articles ID：80019818611,
Web of Science ID：WOS:000259834000002 Anomalous magnetic field effects on photochemical reactions in ionic liquid under ultrahigh fields of up to 28 T Atom Hamasaki; Tomoaki Yago; Tadashi Takamasu; Giyuu Kido; Masanobu Wakasa
JOURNAL OF PHYSICAL CHEMISTRY B,
Volume：112,
Number：11,
First page：3375,
Last page：3379, Mar. 2008
The magnetic field effects (MFEs) on photoinduced hydrogen abstraction reactions between benzophenone and thiophenol in an ionic liquid, N,N,N-trimethyl-N-propylammonium bis(trifluoromethanesulfonyl) imide (TMPA TFSI), were studied by a nanosecond laser flash photolysis technique under ultrahigh fields of up to 28 T. Extremely large and anomalous stepwise MFEs were observed for the first time. The escape yield of benzophenone ketyl radical decreased with increasing magnetic field strength (B) at 0 T < B <= 2 T. The decrease was almost saturated at 2 T < B <= 10 T. At much higher fields (10 T < B <= 28 T), the yield decreased again with increasing B, producing a 25% decrease at 28 T.
AMER CHEMICAL SOC, English
DOI：https://doi.org/10.1021/jp710047cDOI ID：10.1021/jp710047c,
ISSN：1520-6106,
CiNii Articles ID：80019421159,
PubMed ID：18298111,
Web of Science ID：WOS:000253945900016 磁場とナノ細孔を用いた複合反応場での光化学反応制御
若狭 雅信
Volume：6(平成19年度), 2008
磁場とナノ細孔を用いた複合反応場での光化学反応制御
若狭 雅信
総合研究機構研究プロジェクト研究成果報告書, Volume：6(平成19年度), 2008
Studies of germanium-platinum bonds in bis(aryl-substituted germyl)platinum complexes by laser flash photolysis and chemical trapping experiments Kunio Mochida; Yusuke Masukawa; Atsuko Yamada; Mai Yanaga; Masato Nanjo; Hidekazu Arii; Masao Gohdo; Masanobu Wakasa
CHEMISTRY LETTERS,
Volume：37,
Number：1,
First page：62,
Last page：+, Jan. 2008
The UV photolysis of bis(triaryl-substituted germyl)platinum complexes, Pt(Ar3Ge)(2)(PMe2Ph)(2) (Ar = Ph, p-C6H4-SiMe3, and p-C6H4C(CH3)(3)) in THF at room temperature results in Ge-Pt bonds homolysis to give the corresponding germyl radicals.
CHEMICAL SOC JAPAN, English
DOI：https://doi.org/10.1246/cl.2008.62DOI ID：10.1246/cl.2008.62,
ISSN：0366-7022,
eISSN：1348-0715,
CiNii Articles ID：10020147828,
Web of Science ID：WOS:000252882700029 イオン液体中での光化学反応と磁場効果
若狭 雅信
Number：5(18年度), First page：525, Last page：526, 2007
イオン液体中での光化学反応と磁場効果
若狭 雅信
総合研究機構研究プロジェクト研究成果報告書, Number：5(18年度), First page：525, Last page：526, 2007
光触媒反応の磁場効果とメカニズム解明
若狭 雅信
Number：4(17年度), 2006
光触媒反応の磁場効果とメカニズム解明
若狭 雅信
総合研究機構研究プロジェクト研究成果報告書, Number：4(17年度), 2006
Magnetic field effects on the hydrogen abstraction reaction of triplet 4-methoxybenzophenone with thiophenol as studied by a picosecond laser flash photolysis technique Morino, I; M Wakasa; H Hayashi
MOLECULAR PHYSICS,
Volume：100,
Number：9,
First page：1283,
Last page：1289, May 2002
The hydrogen abstraction reaction of triplet 4-methoxybenzophenone with thiophenol at 265 K has been studied with a newly developed picosecond laser flash photolysis apparatus under magnetic fields of 0-1.7 T. The decay rate constant of the radical pair generated was found to increase from 3.42 x 10(9) s(1) to 4.15 x 10(9) s(1) with increasing the magnetic field from 0 to 1.7 T. The observed magnetic field effects can be explained by the Deltag mechanism. Using the simple kinetics model with the Deltag mechanism, the rate constant of the escape process from the pair (k(esc)) and two rate constants for the T-S spin conversion process (k(T-S)) at 0 and 1.7 T were found to be 1.97 x 10(9) s(1), 1.45 x 10(9) s(1), and 2.12 x 10(9) s(1), respectively. From the magnetic field dependence on k(T-S), the difference in the g values of the 4-methoxybenzophenone ketyl and phenylthiyl radicals was estimated to be 0.0087.
TAYLOR & FRANCIS LTD, English
DOI：https://doi.org/10.1080/00268970110109745DOI ID：10.1080/00268970110109745,
ISSN：0026-8976,
Web of Science ID：WOS:000175511300001 Re-examination of the magnetic field effects on the thermal reactions of benzyl and pentafluorobenzyl halides with n-butyllithium in hexane M Wakasa; H Hayashi
MOLECULAR PHYSICS,
Volume：100,
Number：8,
First page：1099,
Last page：1105, Apr. 2002
The magnetic field effects reported in 1973 for the thermal reaction of benzyl and pentafluorobenzyl chlorides with n-butyllithium in hexane have been re-examined under various reaction conditions. Using a new reaction apparatus, which has an electromagnet (up to 1.49 T) in a glove box under an argon atmosphere (H2O and O-2 < 1 ppm), a study has been made on the effects on the yields of asymmetrical products (phenylpentane and pentafluorophenylpentane) and symmetrical ones (diphenylethane and decafluorodiphenylethane) in the absence and presence of external magnetic fields. No appreciable magnetic field effects have been observed with change of sample concentration, reaction temperature, or magnetic field strength, or with various benzyl halides.
TAYLOR & FRANCIS LTD, English
DOI：https://doi.org/10.1080/00268970110109754DOI ID：10.1080/00268970110109754,
ISSN：0026-8976,
Web of Science ID：WOS:000174955900007 Novel Photocycloaddition of Aromatic Ketones to Cyclic Oligosilanes
KAKO Masahiro; GU Mei; TAKENAKA Yohei; TAKAGI Kentaro; KONDO Kazuhiro; NAKADAIRA Yasuhiro; WAKASA Masanobu; HAYASHI Hisaharu
Volume：2001, Number：12, First page：1220, Last page：1221, 05 Dec. 2001
English
ISSN：0366-7022, CiNii Articles ID：10007540778, CiNii Books ID：AA00603318
Time-resolved EPR and ODMR studies on the lowest excited triplet states of alpha-silyl and alpha-germyl ketones ISM Saiful; M Hanaya; M Iwaizumi; M Wakasa; K Mochida; M Mukai; N Hirota; S Yamauchi
MOLECULAR PHYSICS,
Volume：99,
Number：14,
First page：1183,
Last page：1192, Jul. 2001
Sublevel properties of the lowest excited triplet (T-1) n pi* states of alpha -silyl and alpha -germyl ketones were examined by means of ODMR, time-resolved EPR and optical spectroscopy. The EPR parameters, D, E and g, population ratios, and triplet lifetimes were obtained. The D value and the triplet lifetime varied among the molecules. In contrast the E value and population ratio remains nearly the same. These properties together with their solvent dependence and emission properties are interpreted in terms of spin-orbit couplings between T-1 (n pi*) and higher S-1 (n pi*), T-2 (pi pi*) and S-2 (pi pi*) states. An origin of the remarkable red-shifts of (1,3)(n pi*) are discussed based on a model of delocalized n, pi and pi* electrons over the Si and Ge atoms. This model is also consistent with all the triplet properties obtained.
TAYLOR & FRANCIS LTD, English
DOI：https://doi.org/10.1080/00268970110043982DOI ID：10.1080/00268970110043982,
ISSN：0026-8976,
Web of Science ID：WOS:000169438700003 Time-resolved EPR and ODMR studies on the lowest excited triplet states of alpha-silyl and alpha-germyl ketones ISM Saiful; M Hanaya; M Iwaizumi; M Wakasa; K Mochida; M Mukai; N Hirota; S Yamauchi
MOLECULAR PHYSICS,
Volume：99,
Number：14,
First page：1183,
Last page：1192, Jul. 2001
Sublevel properties of the lowest excited triplet (T-1) n pi* states of alpha -silyl and alpha -germyl ketones were examined by means of ODMR, time-resolved EPR and optical spectroscopy. The EPR parameters, D, E and g, population ratios, and triplet lifetimes were obtained. The D value and the triplet lifetime varied among the molecules. In contrast the E value and population ratio remains nearly the same. These properties together with their solvent dependence and emission properties are interpreted in terms of spin-orbit couplings between T-1 (n pi*) and higher S-1 (n pi*), T-2 (pi pi*) and S-2 (pi pi*) states. An origin of the remarkable red-shifts of (1,3)(n pi*) are discussed based on a model of delocalized n, pi and pi* electrons over the Si and Ge atoms. This model is also consistent with all the triplet properties obtained.
TAYLOR & FRANCIS LTD, English
DOI：https://doi.org/10.1080/00268970110043982DOI ID：10.1080/00268970110043982,
ISSN：0026-8976,
Web of Science ID：WOS:000169438700003 Magnetic field effects on the dynamic behavior of a radical pair as studied by a sub-nanosecond laser flash photolysis technique M Wakasa; H Hayashi
CHEMICAL PHYSICS LETTERS,
Volume：327,
Number：5-6,
First page：343,
Last page：350, Sep. 2000
The hydrogen abstraction reaction of triplet 4-methoxy-benzophenone with thiophenol at 265 K was studied by a sub-nanosecond laser flash photolysis technique in the absence and presence of a magnetic field of 1.75 T. The decay rate of the generated radical pair at zero field was found to be 1.1 X 10(9) s(-1) and that at 1.75 T to be 1.8 X 10(9) s(-1). The observed magnetic field effect can be explained by the acceleration of the triplet-singlet spin conversion process due to the Delta g mechanism. (C) 2000 Published by Elsevier Science B.V.
ELSEVIER SCIENCE BV, English
DOI：https://doi.org/10.1016/S0009-2614(00)00894-0DOI ID：10.1016/S0009-2614(00)00894-0,
ISSN：0009-2614,
CiNii Articles ID：80011903699,
Web of Science ID：WOS:000089301900013 Magnetic field effects due to the Delta g mechanism upon chemical reactions through radical pairs under ultrahigh fields of up to 30 T M Wakasa; K Nishizawa; H Abe; G Kido; H Hayashi
JOURNAL OF THE AMERICAN CHEMICAL SOCIETY,
Volume：121,
Number：39,
First page：9191,
Last page：9197, Oct. 1999
Magnetic field effects (MFEs) due to the isotropic ag mechanism were studied for the hydrogen abstraction reactions of 4-methoxy-benzophenone with thiophenol in several solvents at 293 K by a laser flash photolysis technique under ultrahigh magnetic fields of up to 30 T. In 2-propanol, ethanol, and methanol, the yield of the escaped ketyl radical decreased with increasing magnetic field from 0 to 30 T. In 2-methyl-1-propanol, however, the decrease was almost saturated at 20 T and the yield above 20 T reduced to be 2/3 Of that at 0 T. Such saturation of the MFEs due to the isotropic Delta g mechanism in the reaction through radical pairsin solution was found for the first time.
AMER CHEMICAL SOC, English
DOI：https://doi.org/10.1021/ja9912776DOI ID：10.1021/ja9912776,
ISSN：0002-7863,
CiNii Articles ID：80011394122,
Web of Science ID：WOS:000083009700025 Mechanism of the reaction of tri-n-butylstannyl anion with n-butyl bromide and iodide as studied by the Sn-119 CIDNP technique M Wakasa; T Kugita
ORGANOMETALLICS,
Volume：18,
Number：16,
First page：2941,
Last page：2943, Aug. 1999
The mechanism of the reaction of the tri-n-butylstannyl anion with n-butyl bromide and iodide in THF was studied by the chemically induced dynamic nuclear polarization (CIDNP) technique. Strong Sn-119 CIDNP spectra were observed for the first time. The emissive CIDNP phase of the tetra-n-butylstannane proves that radical intermediates are involved in the present reactions.
AMER CHEMICAL SOC, English
DOI：https://doi.org/10.1021/om990094pDOI ID：10.1021/om990094p,
ISSN：0276-7333,
CiNii Articles ID：80011262185,
Web of Science ID：WOS:000081997400006 Mechanism of the Reactions of Tri-n-butylstannyl Anion with n-Butyl Bromide and Iodide As Studied by the 119Sn CIDNP Technique Organometallics,
Volume：18,
Number：16,
First page：2941,
Last page：2943, 1999
DOI：https://doi.org/10.1021/om990094pDOI ID：10.1021/om990094p,
ISSN：0276-7333,
CiNii Articles ID：80011262185 Enrichment of germanium-73 with the magnetic isotope effect on the hydrogen abstraction reaction of triplet benzophenone with triethylgermane in an SDS micellar solution M Wakasa; H Hayashi; K Ohara; T Takada
JOURNAL OF THE AMERICAN CHEMICAL SOCIETY,
Volume：120,
Number：13,
First page：3227,
Last page：3230, Apr. 1998
Using the hydrogen abstraction reaction of triplet benzophenone with triethylgermane in an SDS micellar solution, we succeeded in enriching Ge-73 with the magnetic isotope effect. At zero magnetic field, 0.5% enrichment of Ge-73 was observed for the cage product (diphenyl(triethylgermyl)methanol). With increasing magnetic field strength (B), the enrichment of Ge-73 increased initially, attaining the maximum value of 5.3% at 500 G. At higher fields (500 G < B less than or equal to 10 kG), it decreased gradually, becoming 1.0% at 10 kG. The magnetic field dependence of the enrichment of Ge-73 can be explained by the relaxation mechanism.
AMER CHEMICAL SOC, English
DOI：https://doi.org/10.1021/ja9739493DOI ID：10.1021/ja9739493,
ISSN：0002-7863,
CiNii Articles ID：80010230264,
Web of Science ID：WOS:000073072700027 Magnetic field effects on the hydrogen abstraction reactions of triplet benzophenone with thiophenol in nonviscous homogeneous solutions
M Wakasa; H Hayashi
JOURNAL OF PHYSICAL CHEMISTRY, Volume：100, Number：39, First page：15640, Last page：15643, Sep. 1996
The hydrogen abstraction reaction of triplet benzophenone with thiophenol at room temperature was investigated in several nonviscous homogeneous solutions (eta = 0.29-3.33 cP) by means of a nanosecond laser flash photolysis technique under magnetic fields of 0-10 T. The escape yield of the benzophenone ketyl radical decreased with increasing magnetic field strength from 0 to 10 T. In 2-methyl-1-propanol (eta = 3.33 cP), the yield at 10 T reduced to 80 +/- 2% of that at 0 T. The observed magnetic field effects can be interpreted by the Delta g mechanism when the geminate recombination process is faster than or comparable to the escape one.
AMER CHEMICAL SOC, English, Report scientific journal
ISSN：0022-3654, Web of Science ID：WOS:A1996VK04600004
ANOMALOUS MAGNETIC-FIELD EFFECTS OBSERVED IN THE REACTION OF A TRIPLET BIRADICAL INVOLVING AN O-CENTERED RADICAL M WAKASA; H HAYASHI
JOURNAL OF PHYSICAL CHEMISTRY,
Volume：99,
Number：47,
First page：17074,
Last page：17077, Nov. 1995
The hydrogen abstraction of a benzophenone-phenol chain-linked compound was investigated in acetonitrile by means of a nanosecond laser flash photolysis technique at magnetic fields of 0-1.7 T. The Lifetime and the initial yield of a triplet biradical involving the benzophenone ketyl and phenoxyl radicals decreased with increasing magnetic field strength (B) from 0 to 0.005 T, but it increased with increasing B from 0.005 to 0.2 T. In a high-field region (0.2 T < B less than or equal to 1.7 T), the lifetime did not change appreciably, but the initial yield of the biradical decreased with increasing B. These anomalous magnetic field effects may be interpreted by the level-crossing mechanism at the low-field region and the Delta g mechanism at the high-field one.
AMER CHEMICAL SOC, English, Report scientific journal
DOI：https://doi.org/10.1021/j100047a004DOI ID：10.1021/j100047a004,
ISSN：0022-3654,
CiNii Articles ID：80008686803,
Web of Science ID：WOS:A1995TF81100004 SEPARATION OF MAGNETIC-FIELD EFFECTS ON THE PHOTOREDUCTION OF XANTHONE WITH P-AMINOTHIOPHENOL INTO THE EFFECTS DUE TO THE DELTA-G AND RELAXATION MECHANISMS
M WAKASA; Y SAKAGUCHI; H HAYASHI
MOLECULAR PHYSICS, Volume：83, Number：4, First page：613, Last page：618, Nov. 1994
The inversion observed at 0.1 T for the magnetic field effects (MFEs) on the photoreduction of xanthone with p-aminothiophenol was investigated in the absence and the presence of a paramagnetic Gd3+ ion with the aid of a laser flash photolysis technique. The MFEs owing to the Delta g and relaxation mechanisms were experimentally separated by the addition of Gd3+. Thus, we have proved for the present reaction that the MFEs owing to the hyperfine coupling mechanism and relaxation mechanism appear in a low field region (below 0.1 T) and that the MFEs owing to the Delta g mechanism gradually appear in a high field region (above 0.1 T).
TAYLOR & FRANCIS LTD, English, Introduction scientific journal
ISSN：0026-8976, Web of Science ID：WOS:A1994PW65000001
LASER FLASH-PHOTOLYSIS OF POLYGERMANES - GENERATION OF GERMYLENES AND POLYGERMYL RADICALS
K MOCHIDA; K KIMIJIMA; H CHIBA; M WAKASA; H HAYASHI
ORGANOMETALLICS, Volume：13, Number：2, First page：404, Last page：406, Feb. 1994
Laser flash photolysis of polygermanes involves both Ge-Ge bond homolysis to give polygermyl radicals and extrusion of germylenes.
AMER CHEMICAL SOC, English, Introduction scientific journal
ISSN：0276-7333, Web of Science ID：WOS:A1994MX33800002
ENRICHMENT OF GE-7O WITH THE MAGNETIC ISOTOPE EFFECT M WAKASA; H HAYASHI; T KOBAYASHI; T TAKADA
JOURNAL OF PHYSICAL CHEMISTRY,
Volume：97,
Number：51,
First page：13444,
Last page：13446, Dec. 1993
The enrichment of germanium-73 with the magnetic isotope effect (MIE) succeeded, for the first time, in the presence and absence of magnetic fields. At 200 G, the photolysis of methyltriphenylgermane in a Brij35 micellar solution under 92.8% conversion gave the 4% enrichment of germanium-73 (alpha = 0.015). Germanium-73 is the heaviest magnetic isotope to have so far been enriched with MIE from samples of natural abundance.
AMER CHEMICAL SOC, English, Report scientific journal
DOI：https://doi.org/10.1021/j100153a006DOI ID：10.1021/j100153a006,
ISSN：0022-3654,
CiNii Articles ID：80007418768,
Web of Science ID：WOS:A1993MP90500006 THE 1ST DIRECT OBSERVATION OF MAGNETIC-FIELD EFFECTS ON THE DYNAMIC BEHAVIOR OF RADICAL PAIRS INVOLVING GROUP 14 SILICON AND GERMANIUM CENTERED RADICALS M WAKASA; Y SAKAGUCHI; H HAYASHI
JOURNAL OF THE AMERICAN CHEMICAL SOCIETY,
Volume：114,
Number：21,
First page：8171,
Last page：8176, Oct. 1992
Laser flash photolysis was performed on micellar solutions and oil emulsions of organosilicon and organogermanium compounds ((aryl)nMen-4E: E = Si or Ge) in the absence and presence of magnetic fields at room temperature. The dynamic behavior of the silyl and germyl radicals formed upon decomposition of the triplet states was directly observed. The lifetime of the radical pair of group 14 clement centered and aryl radicals and the yields of the escaped silyl and germyl radicals were observed to increase with magnetic field strength increasing from 0 to 1.35 T.
AMER CHEMICAL SOC, English
DOI：https://doi.org/10.1021/ja00047a028DOI ID：10.1021/ja00047a028,
ISSN：0002-7863,
CiNii Articles ID：80006728632,
Web of Science ID：WOS:A1992JR86300028 PHOTOCHEMISTRY OF PHENYL-SUBSTITUTED DIGERMANOXANE - 1ST DIRECT OBSERVATION OF GERMOXY RADICALS PROBED BY LASER FLASH-PHOTOLYSIS
K MOCHIDA; C YOSHIZAWA; S TOKURA; M WAKASA; H HAYASHI
POLYHEDRON, Volume：10, Number：19, First page：2347, Last page：2349, 1991
Laser flash photolysis of the phenyl-substituted digermanoxanes (PhnMe3-nGe)2O (n = 1-3) results in Ge-O bond homolysis to give germyl radicals and germoxy radicals.
PERGAMON-ELSEVIER SCIENCE LTD, English, Introduction scientific journal
ISSN：0277-5387, Web of Science ID：WOS:A1991GQ39600016
UV AND ESR STUDIES OF TRIPHENYL-SUBSTITUTED GROUP-4B ELEMENT (SILICON, GERMANIUM, AND TIN) CENTERED RADICALS IN MATRIX AT LOW-TEMPERATURE
M WAKASA; K HORIUCHI; K MOCHIDA
NIPPON KAGAKU KAISHI, Number：8, First page：1469, Last page：1471, Aug. 1989
CHEMICAL SOC JAPAN, Japanese, Introduction scientific journal
ISSN：0369-4577, Web of Science ID：WOS:A1989AM53900047
LASER PHOTOLYSIS OF ARYL-SUBSTITUTED DIGERMANES - GENERATION OF GERMYL RADICALS AND GERMYLENES
K MOCHIDA; M WAKASA; Y NAKADAIRA; Y SAKAGUCHI; H HAYASHI
ORGANOMETALLICS, Volume：7, Number：8, First page：1869, Last page：1871, Aug. 1988
AMER CHEMICAL SOC, English, Introduction scientific journal
ISSN：0276-7333, Web of Science ID：WOS:A1988P775000029
