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The temperature (T) dependences of the emission spectra and lifetimes of octahedral hexanuclear molybdenum(II) ([{Mo6Cl8}Cl6]2− = [1]2−), rhenium(III) ([{Re6S8}Cl6]4− = [2]4−), and tungsten(II) clusters ([{W6Cl8}Cl6]2− = [3]2−) in crystalline or poly(methyl methacrylate) (PMMA) phases were studied. The emission spectrum of the cluster showed a lower-energy shift upon heating from 3 to 70 K, while that shifted gradually to higher-energy above 70 K. The emission spectral shifts of the cluster upon T-elevation accompanied sharp ( 50 K) in the emission lifetime. Such T-dependent emission characteristics, commonly observed for these three cluster complexes, were analyzed by assuming the contribution of the emissions from the excited triplet state spin-sublevels. The large T dependences of the emission lifetimes and spectra of the hexanuclear Mo(II), Re(III), and W(II) clusters can be understood by a single context of the contributions of the emissions from the excited triplet stat...

An introduction of two arylborane charge transfer (CT) units to the periphery of 1,10-phenanthroline (B2phen) or 2,2′-bipyridine (B2bpy) in a tricarbonyl rhenium(I) diimine complex (fac-[Re(CO)3(B2phen)Br] = ReB2phen or fac-[Re(CO)3(B2bpy)Br] = ReB2bpy) resulted in unique redox, spectroscopic, and photophysical properties of the complex. In particular, the presence of the two arylborane units in the complex can enhance its metal-to-ligand CT absorption intensity in the visible region and the radiative rate constant, compared to those of the complexes without and with the single arylborane unit in the ligand. The single X-ray crystal structure of ReB2phen is also reported.

We demonstrate that phase separation of an aqueous poly(vinyl methyl ether) (PVME) solution can be triggered not only by a temperature change but also by photon pressure. A near-infrared continuous...

Polymer microchannel chips (100 μm width × 20 μm depth) integrated with electrodes were fabricated and applied to a one-step electrochemical cyanation reaction of pyrene (PyH). An acetonitrile solu...

A laser trapping picosecond fluorescence microspectroscopy system was combined with a high pressure cell to study droplet size and pressure effects on chemical phenomena in single micrometer-sized oil droplets. When a rectangular capillary tube was used as a pressure cell, single oil droplets were easily and stably trapped by a 1064-nm laser beam even under high pressure. The developed system enabled us to pressurize a sample emulsion as high as 75 MPa; such pressure was enough to induce pressure and droplet-size effects on the fluorescence dynamics of an Acridine Orange derivative (C12-AO+) in single oil droplets. In particular, droplet-size effects on the fluorescence dynamics were pronounced with an increase in static pressure. Possible origins of the pressure and droplet-size effects were discussed.

Structures and characteristics of water/oil interfaces at the molecular level are reviewed. Dynamic fluorescence anisotropy of Sulforhodamine 101 (SR101) and excitation energy transfer from SR101 to Acid Blue 1 (AB1) at water/oil interfaces were studied by using time-resolved total internal reflection (TIR) fluorometry. The results indicated that a water/carbon tetrachloride (CCl4) interface was sharp with respect to the molecular size of SR101 (∼10 A), while a water/1,2-dichloroethane (DCE) interface was relatively rough compared to the water/CCl4 interface. The present results were also compared with those predicted from molecular dynamic simulations and the thermally capillary wave theory. Furthermore, on the basis of fluorescence dynamic measurements of Sulforhodamine B (SRB) adsorbed at a water/oil interface, a relationship between thickness/roughness and the polarity at the interface was discussed.

CdS nanocrystals were prepared in micrometer-sized chelate polymer particles by nucleation of Cd2+ ions with an aqueous Na2S solution. Simulation of the absorption spectral band shapes of CdS under an effective mass approximation was conducted on the basis of the size distributions of the crystals in the polymer, which were estimated by the relevant transmission electron micrograph images. The optical properties and the size distributions of CdS were dependent on the diameter of the polymer particle, when the concentration of an added S2− solution was sufficiently high for rapid nucleation. In the case of the reaction of Cd2+ with a diluted S2− solution, contrarily, the formation of CdS was confined in the surface layer of the host polymer particle with layer-by-layer size distributions. Effects of the host polymer particle size and the concentration of the Na2S solution on the size distributions and the optical properties of CdS are discussed in terms of the apparent rate of nucleation of Cd2+ to CdS.

Kinetic analyses of a sulfonation reaction between electrochemically-generated diethyl(4-imino-3-methyl-2,5-cyclohexylidene)ammonium salt (quinone diimine derivative (QDI) and SO32− in water have been performed by a generation-collection mode of twin-microband electrodes. The collection efficiency of QDI (φ), defined as the ratio of the current at a generator to that at a collector, was dependent on the interelectrode distance and the SO32− concentration. The rate constant of the sulfonation reaction was determined by both a two-dimentional digital simulation of the concentration gradient of QDI and kinetic analyses of the observed φ values.

The phase transition of an aqueous poly(N-isopropylacrylamide) solution (PNIPAM, wt% = 1.8—3.6%) was induced by the irradiation of a focused (ca. 1 μm) 1064-nm laser beam; this brought about the formation of a single PNIPAM microparticle. The diameter of the particle was controlled to 2—9 μm through the laser power, polymer concentration, and solution temperature. The primary origin of particle formation was the photo-thermal phase transition of the polymer solution through the local heating of water (H2O) by the laser beam. The characteristic features of the phenomena, including manipulation of the PNIPAM particle by the incident laser beam and the role of radiation force for the particle formation, are discussed.

Photostimulated volume expansion of polyacrylamide microgels (initial radius = 11—235 μm) bearing triphenylmethyl cyanide moieties (AAm-TPMCN) in water was studied on the basis of simultaneous measurements of the degree of ionic dissociation (α) of TPMCN to TPM+ (triphenylmethyl cation) and the gel radius. The time profile of the radius change, r(t), was analyzed by a convolution relation between r(t) and the time course of α (α(t)). The characteristic time constants of the volume change, related to the cooperative diffusion coefficient of the gel network, were determined for AAm-TPMCN gels with various radii. The faster photoresponse time of the volume change for the smaller AAm-TPMCN gel was explained in terms of the diffusion theory of gel networks in water.

The action of electron transfer sensitization was quantitatively discussed by measuring photooxidative dye formation of leuco Crystal Violet (LCV) in the perylene (Pe)-1,4-dicyanobenzene(DCB)–LCV combination in polar media. Under the conditions of exclusive photoexcitation of perylene (λex at 435 nm), the kinetic study revealed that the turn over number of perylene as a sensitizer was immeasurably large in the ternary system in vacuo. This is an indication that perylene is indeed recycled via two successive electron transfer processes. The turn over number decreased to 58 in air, probably due to instability of intermediate ion radicals. The quantum yield was larger for the ternary system than for the binary system(Pe–LCV) irradiated at 435 nm. Although the absolute quantum yield of photooxidation was in the order of 10−3 or less in both systems, the ternary electron transfer system was apparently advantageous since the efficiency of back electron transfer would be reduced when multiple electron transfer p...

The photoreduction of 2-piperidinoanthraquinone (1) by an electron transfer from hydroxide ion in aqueous 2-propanol was reinvestigated. The reaction proceeded actively on irradiation at 365 nm, but very weakly on irradiation at 420 nm. The fluorescence of 1 was not affected by hydroxide ion. 1,3-Cyclohexadiene as a triplet quencher retarded the photoreduction. All results revealed that the reactive state of 1 in the photoreduction is not the intramolecular excited CT state, but the upper excited nπ* triplet state. Kinetic studies indicated that the rate of deactivation from the T2(3nπ*) level of 1 is unusually slow (kd=1.7×108 s−1). The photoreduction via the upper excited T2(3nπ*) level was also observed in 1-amino- and 1-piperidinoanthraquinone, while 2-aminoanthraquinone did not exhibit any reactivity. Wavelength-dependencies (313 nm, 365 nm, and >420 nm irradiations) of the photoreductions were also observed.