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The J aggregate formation of a cyanine dye, pseudoisocyanine (PIC), in the presence of synthetic polyanions, was studied both in aqueous solutions and film states. The dye formed J aggregates at low concentration (2 £ 10 25 M) in the presence of polyacrylic acid, sodium salt (PA) and polyvinyl sulfonic acid, potassium salt (PVS) in solutions, whereas the aggregation can only be formed at relative higher dye concentration (1 £ 10 24 M) in a polystyrenesulfonic acid, sodium salt (PSS) matrix. There existed an optimum condition for the J aggregate formation depending on R, the ratio of the concentration of polymer residue to the dye. R values were ca. 10, two and two for PA, PVS and PSS, respectively. The J aggregate films were fabricated by casting the solutions on glass substrates. The cast films of the dye in the PA and PSS matrices showed a new J band at 585 nm, while those from the PVS matrix were at 573 nm. Higher molecular weights of the polyanions lead to the formation of well-defined J aggregate, both in solution and in film. All the J aggregate films exhibited a chemochromism to HCl and NH3 gases. The J band at 585 nm in the films can be changed to the J band at 575 nm by repeated successive exposure of the films to HCl and NH3 gases, suggesting that the metastable nature of the J aggregate lies at 585 nm. q 2000 Elsevier Science S.A. All rights reserved.

Intersolute hole transfer (A•+ + B → A + B•+) was reinvestigated using nanosecond pulse radiolysis in fluid solutions of dichloromethane (A, biphenyl; B, naphthacene, rubrene). Under our new experimental conditions where the concentration of the second solute [B] was kept higher than 0.5 mM, the kinetics of the hole transfer was observed within 500 ns after irradiation, at which time the geminate recombination process with counterpart anionic species was also observed. On the basis of the analysis with the Smoluchowski equation, the second-order rate constants of hole transfers were successfully obtained. Moreover, we confirmed the existence of another slow oxidation of the second solute B by the solvent neutral radical CH2Cl• formed from the electrons ejected during the initial ionizing process. This reaction is a kind of electron transfer with a charge separation that has never been confirmed, but should generally exist in an irradiated solution of halogenated compounds. In our present case, more than 3...

We present the results of femtosecond optical heterodyne-detected optical Kerr effect spectroscopy (OHD-OKE) on acetophenone and its derivatives: o -hydroxybenzaldehyde, o -methylacetophenone, and o -hydroxyacetophenone. The depolarized Raman scattering spectra were also measured, and compared with the frequency-domain representations of the OHD-OKE data. An oscillatory motion, corresponding to an intramolecular vibrational Raman mode, is clearly detected in the OHD-OKE transient for each of these liquids. The slow orientational relaxation times of o -hydroxybenzaldehyde and o -hydroxyacetophenone imply the existence of strong intermolecular interactions induced by hydrogen bond exchange.

The amphiphilic organic ligand (5-octadecyloxy-2-(2-pyridylazo)phenol, PARC18) formed various colored metal complexes with transition metal ions such as Fe(II), Co(II), Ni(II), Cu(II), Zn(II), VO(II), Ag(I), Cd(II), Hg(II) in monolayers, which were confirmed by the π–A isotherms and in situ absorption spectra of the monolayers. Well-defined LB films of the metal complexes can be fabricated by immersing the LB film of PARC18 ligand into aqueous solutions containing metal ions as verified from absorption spectra. Photoillumination can accelerate the metal complex formation process. The LB films fabricated by such methods are oriented with their functional groups inclined to the surface of the films as verified by the polarized absorption spectra measurement. Colored patterns can be written on the LB films by utilizing the photo-accelerated complex formations of the PARC18 LB film and metal ions. Different colors can be realized using a common PARC18 ligand by changing metal ions.

The aggregation of a long-chain thiacarbocyanine dye (5,5′-dichloro-3,3′-dioctadecyl-9-ethylthiacarbocyanine perchlorate) in monolayers on a subphase containing heparin has been investigated as a function of surface pressure byin situmeasurement of the absorption spectra. Only the monomer band was observed at lower surface pressure, while two J aggregate bands at 648 and 666 nm were observed when the surface pressure was above 25 mN m−1. Their intensities increased with the surface pressure. The H aggregate was observed at higher surface pressure (50 mN m−1). Repeated expansion and compression of the monolayer on the heparin subphase can increase the relative amount of the H aggregates. The spectral changes in the monolayers show that there are reversible and irreversible processes in the compression and expansion cycles. In LB films, the J aggregate was formed even at lower surface pressure. Only the J band at 650 nm is observed in the LB films.

We developed a novel measurement method of the Donnan potential difference at a charged membrane/salt solution interface. The method can measure the potential under the condition that the membrane charge density is much lower than the KCl concentration of the salt bridge. This method is very useful for obtaining the effective charge density of each layer of a bipolar membrane. The present experiments in a system of a negatively charged poly(vinyl alcohol) membrane and a single salt solution of KCl, NaCl, LiCl, CaCl2 and LaC3 revealed that the membrane effective charged density has the same value for all the ions. The experiments in mixed KCl and CaCl2 solution revealed that the potential in the system is governed mainly by the concentration of the counterion having the highest valence in the system.

The visible scintillation around 690 nm from Desmarquest AF995R, which is used for real-time beam monitoring, was investigated on steady state γ-radiolysis at room and low temperatures. The temperature dependence of the scintillation intensity indicates the existence of more than two processes with different activation energies. The newly found growth of the scintillation which continues for over several hours on continuous irradiation shows saturating behavior. Weak residual emissions remaining for over a day after stopping the irradiation were also observed.

The simulations and the experimental data of ionic transport across a bipolar membrane in dialysis systems of a 2−1 type salt, where “2−1 type” means a combination of a bivalent cation and a unival...

Long-chain anils of salicylaldehyde, 2-hydroxy-l-naphthaldehyde and ortho-nitrobenzaldehyde were newly synthesized and the photo-excited hydrogen transfer in the LB films of these compounds was investigated. Hydrogen transfer occurred in all the LB films. The back reaction in the LB films of anils of salicylaldehyde, 2-hydroxy-l-naphthaldehyde was markedly suppressed in comparison with the corresponding solutions. No back reaction was observed in the LB films of derivatives from ortho-nitrobenzaldehyde.

The novel amphiphile 5-(octadecyloxy)-2-(2-thiazolylazo)phenol (TARC18) formed a stable condensed type monolayer at the air/water interface. When transition metal ions such as Fe(II), Co(II), Ni(II), Cu(II), Zn(II), and Cd(II) were present in the aqueous subphase, 1:1 complexes of TARC18 with the above metal ions were formed in the monolayers at the air/water interface. The formation of these complexes was verified by measurements of the π−A isotherms and the absorption spectra of the monolayers at the air/water interface in situ. The TARC18 monolayer showed strong ability to incorporate the Cu(II) ion in the subphase, resulting in a larger limiting area and lower collapse pressure of the monolayer on the subphase containing Cu(II) ion in comparison with those on the subphase containing the other metal ions. Moreover, the Cu(II) ion was predominantly bound to the TARC18 monolayer when all the above ions coexisted in the subphase.

The complex formation of an organized Langmuir−Blodgett (LB) film with transition metal ions in aqueous solutions was observed. The LB film of 5-(octadecyloxy)-2-(2-thiazolylazo)phenol (TARC18)) co...

A chemiluminescence scintillator was proposed as a possible scintillator in an aqueous solution where the usual scintillators do not function. The new scintillator is based on chemiluminescence in which an active chemical species induced by irradiation of water is involved. An alkaline luminol solution containing H2O2 was examined from this viewpoint.

Two-dimensional aggregation of a long-chain thiacarbocyanine dye 5,5‘-dichloro-3,3‘-dioctadecyl-9-ethylthiacarbocyanine perchlorate in the monolayers on subphases containing different synthetic polyanions were studied. The aggregation process of the dye in the monolayers was followed by the in situ measurement of the absorption spectra of the monolayers. Two J aggregates were observed at 648 and 666 nm in the monolayer on a plain water surface at all the surface pressures. On the subphase containing poly(acrylic acid), sodium (PAA), and poly(vinyl sulfonic acid), potassium salt (PVS) subphases, the J aggregates were formed at relative high surface pressures (15 and 17.5 mN/m, respectively). On the PVS subphase, an H aggregate at 472 nm was also observed at higher surface pressure (>40 mN/m). On the poly(styrenesulfonic acid), sodium salt (PSS) subphase, neither J nor H aggregates were observed even at higher surface pressures. Models were proposed to explain these interactions between the positively charg...

Charge transfer between Ru(bpy) 2+ 3 (where bpy is 2,2′-bipyridine) complexes incorporated into a Nafion® membrane has been investigated using in situ spectrocyclic voltammetry and statistical calculation of the intermolecular distance between the complexes. The membrane was prepared either by a mixture casting method in which an alcoholic mixture solution of Nafion and the complex was cast to form a membrane, or by an adsorption method in which the complex was adsorbed from its aqueous solution into a precoated Nafion® membrane. It has been found that the electrochemical reactivity of the complex in a membrane prepared by the adsorption method is much higher than that prepared by the mixture casting method. The charge transfer distance between the complexes ( R 0 ) in the membrane prepared by the adsorption method was 1.6 nm (scan rate, 2 mV s −1 ; pH 5.5), when assuming a random dispersion of the complex, which is significantly longer than that (1.1 nm) in the membrane prepared by the mixture casting method. The emission lifetime of the photoexcited Ru(bpy) 2+ 3 in the membrane suggests that the complex is localized in the membrane when it is prepared by an adsorption method; such localization would make the calculated R 0 value greater than the real value. The fraction of the volume in the membrane where the complex is adsorbed was estimated as 20 ± 3%, by comparing the real local complex concentration in the membrane obtained from the R 0 value (1.1 nm) for the mixture casting system with the apparent average complex concentration.

A calculation method was derived for ionic transport across a bipolar membrane in dialysis systems of mixed salt solutions containing multivalent ions. The calculation of the total membrane potential in the solutions containing KCl alone by this method shows that the potential-salt concentration curve depends both on the direction of the arrangement of the membrane charged layers to the concentration gradient of the salt solutions and on the ratio of the charge densities of the two charged layers. The simulations based on experimentally determined parameters agree with the potential measurements for bipolar membranes produced so that the transport properties depend mainly on their charges. 40 refs., 4 figs., 1 tab.

The in situ spectrocyclic voltammetric investigations of the dimeric ruthenium complex used for water oxidation, [(bpy) 2 (H 2 O)Ru-O-Ru(H 2 O)(bpy) 2 ] 4+ (H 2 O-Ru III -Ru III -OH 2 ), were carried out in a homogeneous aqueous solution and in a Nafion membrane under different pH conditions. The in situ absorption spectra recorded for the dimer show that the dimer H 2 O-Ru III -Ru III -OH 2 complex underwent reactions initially to give the detectable H 2 O-Ru III -Ru IV -OH and H 2 O-Ru III -Ru IV -OH 2 complexes, and at higher positive potentials, this oxidized dimer underwent further oxidation to produce a presumably higher oxidation state RuV-RuV complex. Since this RuV-RuV complex is reduced rapidly by water molecules to H 2 O-Ru III -Ru IV -OH 2 , it could not be detected by absorption spectrum. Independent of the pH conditions and homogeneous solution/Nafion membrane systems, the dimer RuIII-RuIV was detected at higher potentials, suggesting that the dimer complex acts as a three-electron oxidation catalyst. However, in the Nafion membrane system it was suggested that the dimer complex may act as a four-electron oxidation catalyst. While the dimer complex was stable under oxidation conditions, the reduction of the dimer Ru III -Ru III to Ru II -Ru II led to decomposition, yielding the monomeric cis-[Ru(bpy) 2 (H 2 O) 2 ] 2+ .

To describe the diffusion of ions in a water-swollen membrane, we improved the Nernst-Planck equation of ion flux by considering a frictional force generated by the collision of ions with membrane matrix which depends on membrane potential. This new equation of ion flux predicts that the apparent mobility of an ion in a membrane depends on both the membrane potential and the valence of the ion. The experimental data of diffusion in dialysis systems of KCl, LiCl, CaCl[sub 2], and LaCl[sub 3] were consistent with the predictions based on this equation. 34 refs., 6 figs.

Catalytic oxidation of water by Ru(bpy)3 3+ in the presence of Co2+ ions, well known in homogeneous solution, has been investigated in thin Nafion layers. Nafion layers on ITO electrodes were equilibrated with Ru(bpy)3 2+. Ru(bpy)3 3+ was produced by electrochemical oxidation after which the electrode was transferred into the reaction cell containing buffered Co2+ solution. The build up of Ru(bpy)3 2+ absorbance at 454 nm was followed spectrophotometrically. The reaction rate is proportional to [Ru(III)], [Co2+] and [HPO4 2-]. We found no evidence for a pH effect in the range 6–8, and no inhibition by Ru(II). A limiting rate of formation of Ru(II) is observed at high Co2+ or phosphate ion concentrations. At high local concentration of the Ru complex in the Nafion layer (~ 0.5 M), two Ru(II) formation processes are observed, their rates differ by one order, but other features (effects of [Ru(III)], [Ru(II)], [Co2+], phosphate and pH) remain unchanged. These results are in contrast with homogeneous solution where the rate of build up of Ru(II) has been previously reported to be proportional to [Ru(III)], [Co2+] and [OH-]2, and inversely proportional to [Ru(II)]. A mechanism is proposed which accounts for these observations.

An amperometric sensor based on the pH-dependent electrode reduction of platinum oxide was developed for monitoring carbon dioxide in the atmosphere. The sensor, using a gas-permeable platinum oxide electrode and aqueous electrolytic solution, could measure the CO 2 concentration without interference from oxygen reduction. The platinum oxide electrode was formed on a gas-permeable PTFE membrane by reactive sputter coating. It was found that platinum oxide is much better for CO 2 sensors than platinum. At the optimum electrode potential, the reduction current was found to be proportional to the square root of the CO 2 gas concentration, indicating that the electrode reduction is controlled by the hydrogen ion concentration supplied from CO 2

The ion permeation in a model system of hemodialysis was simulated in terms of a theory based on the Nernst-Planck equation of flux and the Donnan equilibrium. The simulations lead to new improved dialysis methods for efficient removal of serum phosphate which utilize a positively charged membrane dialyzer and/or polycation dialysate solution. Preliminary experiments of ion permeation in the model system were done for the examination of the simulations

The [Ru(NH3)6]3+ complex is shown to be a two-electron catalyst for homogeneous as well as heterogeneous water oxidation to evolve dioxygen. The oxygen evolution is proposed to proceed by two molecules of the complex through a peroxo-bridged intermediate involving higher oxidation state [Ruv(NH3)6]5+.

A theory is presented for ion transport across ion-exchange membranes in multicomponent ionic systems. The theory, formulated on the basis of both the Donnan equilibrium and the Nernst-Planck equation of flux, enables us to simulate uphill transport of ions in a nonstationary dialysis system by numerical computation. The simulations and the experimetal data for membranes made of poly(vinyl alcohol) and poly(styrenesulfonic acid) revealed that the maximum ion concentration ratio of the bulk phases at either side of the membrane depends on both the membrane charge density and the ionic mobilities

The transient photoreflectance induced by a 6-ns laser pulse was measured for a cadnium sulfides single-crystal electrode in aqueous solution with 1 M sodium sulfite an a reducing agent. Though the electrode used was a single crystal, the photoreflectance sprectrum obtainod resembled EER sprectra of low structural quality such as sputtered or painted thin films. The time evolution of the spectrum intensity agreed with that of the excitation pulse

The electrochemical reduction of carbon dioxide has been studied on metal or surface-modified metal cathodes and semiconductor photocathodes [l-7]. The reaction pathway and the efficiency strongly depend on the electrode material [2,4]. The reduction of carbon dioxide results from the addition of hydrogen followed by the subtraction of the oxygen atom. The electrode surface must be hydrogen-rich to function as a hydrogen source, and parly oxidizable to function as an oxygen sink and to allow the adsorption of carbon dioxide molecules. Titanium, platinum and nickel electrodes show a strong affinity for hydrogen atoms [Sl. However, previous studies on the electrochemical reduction of carbon dioxide on these electrodes in aqueous media have revealed that the major product is hydrogen and the efficiency of the carbon dioxide reduction is low [2,4]. This low efficiency results from either poor adsorption of carbon dioxide or an adsorption state unfavorable for succeeding steps. Inclusion of a second element in the electrode material may improve surface properties. Boron is a promising candidate for the second element; it can form B-O and B-C bonds [9] that serve to accumulate carbon dioxide on the surface, and metal borides provide a variety in stoichiometry [9] that increases the chance for the partial oxidation by carbon dioxide for the oxygen subtraction. This preliminary note is concerned with the properties of a titanium diboride (TiB,) cathode in the electrochemical reduction of carbon dioxide. Titanium diboride is an electroconductive ceramic and an atomically homogeneous mixture of titanium and boron.

Neutron emissions from electrolysis of D 2 O with palladium and palladium-titanium electrodes as well as from pressurized D 2 gas with titanium alloys have been measured. The neutron detector system was so designed to have very low background condition. Neutron-γ separation technique using liquid scintillator was applied to obtain essentially no γ ray background condition for neutron counting. Special care was taken to stabilize the detection system using event-by-event data recording. No significant signal of neutron emission was observed. Upper limits of emission probability of neutron have been determined to be 6×10 -3 s -1 , 1×10 -2 s -1 , and 2.3×10 -2 s -1 for Pd electrode, Pd-Ti electrode, and pressurized gas systems. These values are orders of magnitude lower than that presented by Jones paper (0.4 s -1 ).

The fluorescence of pyrene and five other aromatic hydrocarbons solubilized with caffeine in aqueous solution was quenched by 0.001–1mol dm−3 sulfuric acid; this quenching did not occur in the absence of caffeine. Exceptionally a non-alternative hydrocarbon, fluoranthene, showed an increase of the fluorescence intensity by the acid. The observed quenching rate was explained by the rate of energy transfer from the aromatic molecules to protonated caffeine in the complex.

A water-insoluble copolymer pendant ruthenium-mercury complex (poly-Ru(bpy) 2+ 3 · [Hg 2 Cl 6 ] 2− ) (denoted poly-Ru-Hg) was prepared from a water-soluble Ru(bpy) 2+ 3 pendant complex of the copolymer of N -vinylpyrrolidone and 4-methyl-4′-methyl-2,2′ -bipyridine (denoted poly-Ru). The poly-Ru-Hg complex was characterized by IR, visible absorption and emission spectroscopies and emission decay measurements. The solubility and excited state lifetime both in dimethylformamide (DMF) solution and film state were quite different from those of the low molecular Ru-Hg complex reported before. The emission from the excited poly-Ru-Hg was much longer than that from poly-Ru in DMF solution while, in a film state, it had a shorter lifetime that the poly-Ru. The quenching of the excited ruthenium complexes by oxygen was studied. The quenching of the excited poly-Ru-Hg by oxygen was prohibited probably because of the cluster nature of the complex.

A CdS single-crystal photoelectrode in aqueous solution containing sodium sulfite was subjected to two-color excitation. The photocurrent caused by UV excitation was markedly enhanced by simultaneous sub-bandgap excitation; no photocurrent occurred for the sub-bandgap excitation alone. The enhancement is explained in terms of passivation of a recombination center by sub-bandgap excitation. The presence of such a recombination center is supported by photocapacitance measurement. Polarized two-color excitation and electrolyte electroreflectance spectroscopy revealed that the recombination center is not localized on the uppermost surface layer but penetrates inside.

The monolayer formation of a series of 2-substituted benzimidazoles at the air/water interface was studied by the measurements of surface pressure-area isotherms. Concentrated silver(I) ion in the subphase can induce the monolayer formation of 2-alkylbenzimidazole derivatives (BzCn) with the alkyl chain equal to or greater than C5 although the derivatives cannot form monolayers on pure water surface except BzC17. Similar behavior of monolayer formation of 2-phenylbenzimidazole was also observed. The measurements of UV spectra and X-ray photoelectron spectroscopy analysis of the transferred films suggested that such monolayer formation was fulfilled through an in situ formation of a polymeric silver(I)−benzimidazole complex at the air/water interface.

The existence of methyl radicals in the photo-Kolbe reaction was confirmed by means of in situ measurements with flow electron spin resonance for deuterated acetic acid. From the dependence of the flow rate, two reaction paths were deduced for methyl radical formation. These were assigned to those caused by trapped holes and •OH radicals. It is suggested that the former path is dominant when platinum has not been loaded onto TiO2 powder.

Self-sustained potential oscillation was observed on a polycrystalline platinum ring electrode under the galvanostatic (constant current) electrochemical oxidation of formaldehyde in a rotating ring-disk electrode cell. When a pulsed stream of hydrogen was supplied to the ring electrode from the disk electrode, the self-sustained oscillation changed to the forced oscillation under certain conditions

The [Ru(NH3)6]3+ complex is shown to be a two-electron catalyst for homogeneous as well as heterogeneous water oxidation to evolve dioxygen. The oxygen evolution is proposed to proceed by two molecules of the complex through a peroxo-bridged intermediate involving higher oxidation state [Ruv(NH3)6]5+.

In partition equilibria of Ca2+, K+ and Cl– between a swollen charged membrane and an aqueous bath of mixed KCl and CaCl2 electrolytes, the equilibrium concentration of the bivalent ion in the membrane decreases to a minimum value as its concentration in the bath increases. The value of the concentration minimum decreases with increasing KCl : CaCl2 concentration ratio in the bath. Simulations and analysis have been performed on the basis of Donnan distribution theory.

Ethanol glasses were irradiated with high-LET ion beams of 18.0 MeV He, 59.2 MeV C, and 60.5 MeV N at 80K. In all these irradiations, the apparent G -value of the trapped electron decreases with increasing dose. The G -values corrected for the dose effects were evaluated at 0.83 for C ions, 0.91 for N ions, and 1.4 for He ions. The dose dependence for high-LET radiations and the LET effect are discussed.

A sec-butyl chloride glass containing a pair of solutes was ..gamma.. irradiated at 77 K and the yields of the solute cations were measured. For the solute pairs N,N-diethylaniline-biphenyl, pyrene-biphenyl, and benz(..cap alpha..)anthracene-naphthalene, the yield of the cation of the first solute, which is of lower ionization potential than its counterpart (the second solute), was found to be independent of the second-solute concentration. The logarithms of the second-solute-cation yields are linear in the first-solute concentration and a negative slope of the plot agrees with that of the plot of log(y/sub 1//sup 0/-y/sub 1/) vs. the first-solute concentration, where y/sub 1/ is a yield of the first-solute cation and y/sub 1//sup 0/ is a constant. Plots of log(y/sub 2//sup 0/-y/sub 2/) against the second-solute concentration fit a straight line. These remarkable kinetic features were elucidated in terms of selective capture of a different state of holes by each solute. For benz(..cap alpha..)anthracene-pyrene and biphenyl-p-xylene pairs, the semilogarithmic plots do not hold, and the yield of each solute cation depends on the concentration of both solutes. In these cases two solutes capture holes competitively. The competitive capture is regarded as the special case of selective capture where the ionization potentials of twomore » solute are equal or nearly so.« less

The crystal structure of the title compound was determined by X-ray diffraction. The crystals have monoclinic symmetry with a=13.481(5), b=8.285(5), c=l3.092(3) A. β=96.24(3)°, and space group P21⁄n with Z=4. The final R-factor was 0.065 for 2191 independent reflections. The torsion angles of the C–Ph bonds are 47.4(4) and 44.4(4)°. The cyclohexene rings have approximate twist-boat conformations. The molecular structure in the crystal is compared with that in the solution phase, that of (E)-stilbenes, and the results of the molecular mechanics calculations. It is also discussed in relation to the molecular packing.

The visible and near-IR absorption spectra were measured in the course of warming of ..gamma..-irradiated glassy solutions of aromatic hydrocarbons in mixtures of 3-methylpentane-sec-butyl chloride and/or CFCl/sub 3/-CF/sub 2/BrCF/sub 2/Br. Warming-induced bands were assigned to dimer cations, complex cations between monomer cations and a solvent fragment radical, and larger aggregates including tetramer dications and trimer cations. The features of the characteristic bands for each species were discussed.

The electronic absorption spectra of anion radicals produced by γ-ray irradiation of (E)-stilbene (1), indeno[2,1-a]indene (2), 5,6,11,12-tetrahydrochrysene (3), (E)-1,1′-bi-indanylidene (4), and (E)-1,1′,2,2′,3,3′,4,4′-octahydro-1,1′-binaphthylidene (5) in glassy 2-methyltetrahydrofuran solution at 77 K have been measured. Examination of the spectra leads to the following conclusions. (a) The (E)-stilbene skeleton in the anion radical of (1) as well as of (2), (3), and (4) is planar or nearly planar; (b) in the anion radical of (5) immediately after its production, the ethylene bond and the C–Ph bonds are substantially twisted, and on controlled warming or on illumination, the twisting of the ethylene bond is increased.

Declin de fluorescence du pyrene et rendements quantiques des cations pyrenes mesures par photolyse laser dans des solutions de micelles contenant a la fois le pyrene et du dodecylsulfate de Cu (II) a 40°C

The electronic absorption spectra of radical ions produced by γ-ray irradiation of (E)-stilbene and related compounds in frozen matrices were measured. On illumination and on controlled warming, the spectra of the radical ions of sterically uncrowded stilbenes and diphenylacetylene remained almost unchanged, while those of the radical ions of sterically crowded stilbenes changed noticeably. Examination of the spectra and of their changes led to the following conclusions: (a) The relaxed geometry of the radical ions of sterically uncrowded stilbenes is planar or nearly planar; (b) in the unrelaxed geometries of the radical ions of (E)-α,β-dialkylstilbenes the torsion angles of the Ph–C bonds are nearly as large as in the parent molecules, and on relaxation these angles become smaller and the torsion angle of the central ethylenic bond deviates from 0° to a considerable extent; (c) for the radical ions of ortho-substituted (E)-stilbenes the geometrical change on relaxation is comparatively small.

A dynamic photocapacitance method using the pulsed electrode potential was developed for measurement of the charge concentration of photoinduced deep traps and their recombination rates along the depth of the electrode. The validity of this method to bulk states was demonstrated by its application to a deep intervalence state which was found at 2.5 eV below the conduction band. Its absorption constant was estimated at 7.7 {times} 10{sup {minus}3} cm{sup {minus}1} on the assumption of a quantum yield of unity. The trap produced from the deep state by photoexcitation is distributed inside the crystal with a concentration of 10{sup 14} cm{sup {minus}3}; thus, the observed are bulk states. A cross section of trap recombination with electrons was 3.6 {times} 10{sup {minus}19} cm{sup 2}, which suggests that the photoinduced trap is neutral and accordingly the original intervalence state is anionic. Disturbance by surface states was observed in the measurements of the deep state.

Monosubstituted ferrocene derivatives and biferrocene dissolved in a freon mixture were γ-ray irradiated at 78 K. A new absorption band found near the region on 1 × 10 4 cm −1 for the monocations produced from biferrocene and phenylferrocene derivatives was assigned to an electron transfer band from the ferrocenyl and the phenyl group to the iron atom, respectively.

Water oxidation was achieved catalytically by the use of mononuclear ruthenium–ammine complexes and using Ce(IV) as an oxidant. Cyclic voltammetric studies of the mononuclear ruthenium–ammine complexes [Ru(NH3)5Cl]2+ and [Ru(NH3)5(H2O)]3+, have been carried out using Basal Plane Pyrolytic Graphite (BPG) coated with poly(p-styrenesulfonate), Nafion, or Kaolin clay. The electrochemical properties of these ruthenium–ammine complexes show that they can be used as two-electron oxidants for water oxidation. It has also been found that these complexes oxidize water to evolve oxygen in the presence of excess Ce(IV) under homogeneous as well as heterogeneous conditions. The oxygen evolution by means of water oxidation was confirmed by using the H218O isotope in the reaction medium. The water oxidation process was found to be dependent on the ionic strength of the medium. Higher acidic conditions gave higher O2 yields. Heterogeneous catalysis with the Ru complex adsorbed in Kaolin clay was as effective as the homog...

An empirical equation is proposed for the dose dependence of the trapped-electron concentration in γ-irradiated glasses. The equation, if suitable values are given to the parameters, fits the experimental data for organic glasses at 77 K.

Solute-anion yields in ..gamma..-irradiated 2-methyltetrahydrofuran glasses containing two solutes were measured at 77/sup 0/K. For solute pairs of p-benzoquinone (BQ)-biphenyl, BQ-pyrene, 1,4-naphthoquinone (NQ)-biphenyl, and pyrene-biphenyl, the results are summarized as follows. (1) The yield of the anion of the left-hand solute (S1) in each pair is little dependent upon the concentration of the other solute (S2). (2) The logarithm of the S2-anion yield is approximately linear in S1 concentration. The electron affinity of the first solute is larger than that of the second. The results are consistent with a scheme that an electron once trapped in a matrix tunnels to either S1 or S2 to form solute anions and an electron also tunnels from S2/sup -/ to S1. The yield of the anion of each solute in a BQ-NQ pair was found to depend on the concentration of the counterpart, in contrast with the results for the above solute pairs. The results for this pair can be explained in terms of a competitive capture scheme which does not include the tunneling from S2/sup -/to S1. 10 figures, 2 tables.