Silylation improves the photodynamic activity of tetraphenylporphyrin derivatives in vitro and in vivo.

The effects of silyl and hydrophilic groups on the photodynamic properties of tetraphenylporphyrin (TPP) derivatives have been studied in vitro and in vivo. Silylation led to an improvement in the quantum yield of singlet oxygen sensitization for both sulfo and carboxy derivatives, although the silylation did not affect other photophysical properties. Silylation also improved the cellular uptake efficiency for both sulfo and carboxy derivatives, enhancing the in vitro photodynamic activity of the photosensitizer in U251 human glioma cells. The carboxy derivative (SiTPPC4 ) was found to show higher cellular uptake efficiency and in vitro photodynamic activity than the corresponding sulfo derivative (SiTPPS4 ), which indicates that the carboxy group is a more promising hydrophilic group than the sulfo group in the silylated porphyrin. SiTPPC4 was found to show high selective accumulation efficiency in tumors, although almost no tumor selectivity was observed for the nonsilylated porphyrin. The concentration of SiTPPC4 in tumors was 13 times higher than that in muscle 12 h after drug administration. We also studied tumor response after treatment and found that silylation enhanced in vivo photodynamic activity significantly. SiTPPC4 shows higher photodynamic activity than NPe6 with white light irradiation.

Evidence for the specific species of benzyltriethoxysilane derivatives with a high-coordination silicon atom.

Evidence for the specific species of benzyltriethoxysilane derivatives with a high-coordination silicon atom is presented. Nanosecond laser flash photolyses of benzyltriethoxysilane and triethoxysilyldiphenylmethane have been studied in polar and nonpolar solvents. For the transient absorption spectra of benzyltriethoxysilane and triethoxysilyldiphenylmethane in methanol, a characteristic band attributed to the benzyl radical or diphenylmethyl radical was observed at around 317 and 330 nm, with a second-order decay rate constant of 5.7 × 10(9) and 4.2 × 10(9) M(-1) s(-1), respectively. While in cyclohexane, an absorption band attributable to the specific species with a high-coordination silicon atom was observed at around 330 nm with a first-order decay rate constant of 5.7 × 10(4) and 1.2 × 10(4) s(-1) for benzyltriethoxysilane and triethoxysilyldiphenylmethane, respectively. A two-step laser-induced fluorescence study of triethoxysilyldiphenylmethane supports the assignment that the transient absorption bands observed at around 330 nm in methanol and in cyclohexane are ascribed to the diphenylmethyl radical and the specific species of triethoxysilyldiphenylmethane with a high-coordination silicon atom, respectively. The candidates for this specific species with a high-coordination silicon atom have been calculated by means of the TD-DFT method and SAC-CI method, and their molecular structures were discussed.

Synthesis and properties of 5,10,15,20-tetrakis[4-(alkoxysilyl)phenyl]porphyrins: an application of selective deprotection of benzaldehyde diethyl acetals in the presence of alkoxysilyl groups.

Selective deprotection of 4-(alkoxysilyl)benzaldehyde diethyl acetals 1a-1c in the two-solvent system of hydrochloric acid and chloroform gave 4-(alkoxysilyl)benzaldehydes 2a-2c in good yields. Under these conditions, undesired hydrolysis of the alkoxysilyl group was minimized. The reaction of benzaldehydes 2a and 2b with pyrrole in the presence of boron trifluoride diethyl etherate led to 5,10,15,20-tetrakis[4-(alkoxysilyl)phenyl]porphyrins 3a and 3b. The X-ray structural analysis showed that 3b has a planar porphyrin ring and shows typical structural features of porphyrin rings. Hydrolysis-condensation of 3a in the presence of a surfactant afforded a porphyrin-silica hybrid (PSH) as insoluble brown powder. The PSH was found to be amorphous and to consist of aggregated nonspherical micrometre-sized particles with rough surfaces. The PSH has mesopores, and the specific surface area is 330 m(2) g(-1) which increases to 810 m(2) g(-1) upon calcination.

Photophysical property and photostability of J-aggregate thin films of thiacyanine dyes prepared by the spin-coating method.

By use of electrostatic interactions of dye molecules and poly(diallyldimethylammonium chloride) (PDDA), the spin-coating technique has been successfully applied to the preparation of stable J-aggregate thin films of thiacarbocyanine dyes on a polycarbonate or quartz plate. The J-aggregate thin films were prepared by the spin-coating of PDDA aqueous solution on dye thin films prepared on a substrate by the spin-coating of 2,2,3,3-tetrafluoro-1-propanol solution of dyes. Photophysical properties of the dye thin films and J-aggregate thin films were studied by measuring the fluorescence spectra, quantum yields, and lifetimes. Coherent size of the J-aggregates was estimated to be 3-12 by means of the absorption bandwidth (full width at half maximum) or radiative lifetime. Photostability of the J-aggregate thin films was also studied in terms of photodegradation efficiency under argon and oxygen in comparison with the dye thin films, and J-aggregate thin films were found to be more stable than the corresponding dye thin films.

Thermal hysteresis and thickness dependence of the molecular orientation of poly(di-n-hexylsilane) in the film state.

Molecular orientation of poly(di-n-hexylsilane) adsorbed on poly(vinyl alcohol) film has been studied by making use of the stretching technique. Dichroic ratio, Rd, strongly depended on the thickness of poly(di-n-hexylsilane) thin film and the highest value ca. 19 was observed at the film thickness of 110 +/- 30 nm. The thermal hysteresis of the molecular orientation was observed in the heating-cooling cycles. By studying the fluorescence spectrum it was confirmed that a portion of the poly(di-n-hexylsilane) molecules were in transoid conformation even at 320 K, although most of poly(di-n-hexylsilane) molecules were in disordered conformation (conformation D). This poly(di-n-hexylsilane) in transoid conformation is formed in the stretching process and may play a role of crystallization nucleus to induce the whole orientation of the poly(di-n-hexylsilane) in the film state.

Photophysical and photochemical processes of 9,10-dihydro-9-silaphenanthrene derivatives: photochemical formation and electronic structure of 9-silaphenanthrenes.

Photophysical and photochemical processes of 9-methyl- and 9-phenyl-9,10-dihydro-9-silaphenanthrene derivatives have been studied at room temperature and 77 K in comparison with the carbon analogue, 9,10-dihydrophenanthrene. These 9,10-dihydro-9-silaphenanthrene derivatives show smaller fluorescence quantum yield and remarkably larger Stokes shifts than those of the carbon analogue. In contrast, their phosphorescence quantum yields are two times larger than those of the carbon analogue, although the absolute value is not so large (approximately 0.1). Reaction products and intermediates produced by the 266 nm light photolysis have been studied, and it has been confirmed that 9-methyl- and 9-phenyl-9-silaphenanthrenes have been photochemically formed in methylcyclohexane at 77 K, in addition to the formation of radical cations of 9,10-dihydro-9-silaphenanthrene derivatives and the carbon-centered radical: 9-hydro-9-silaphenanthrenyl radical.

Production and excited state dynamics of the photorearranged isomer of benzyl chloride and its methyl derivatives studied by stepwise two-color laser excitation transient absorption and time-resolved thermal lensing techniques.

Production and photoexcited dynamics of reaction intermediates with photolyses of benzyl chloride (BzCl) and methyl-substituted benzyl chlorides (MeBzCls) were studied by using stepwise two-color laser excitation transient absorption (TC-TA) and two-color laser excitation time-resolved thermal lensing (TC-TRTL) measurements. With photoexcitation of BzCl the formation of transient photorearranged isomer was suggested in the previous paper [Res. Chem. Intermed. 2001, 27, 137]. Such an isomer formation for MeBzCls was also observed in a 248 nm excitation. It was found that further photoexcitation of the isomers with the 308 nm light caused photodissociation to yield the corresponding benzyl radicals. The reaction quantum yield and the molar absorptivity of the photorearranged isomer of BzCl were estimated. The heat of reaction for the photodissociation of the isomer was successfully determined with the TC-TRTL measurement. These experimental results were consistent with MO calculations.

Laser-induced fluorescence of cyclohexadienyl (c-C6H7) radical in the gas phase.

A laser-induced fluorescence spectrum was observed in the 500-560 nm region when a mixture of 1,4-cyclohexadiene and oxalyl chloride was photolyzed at 193 nm. The observed excitation spectrum was assigned to the A (2)A(2)<--X (2)B(1) transition of the cyclohexadienyl radical c-C6H7, produced by abstraction of a hydrogen atom from 1,4-cyclohexadiene by Cl atoms. The origin of the A<--X transition of c-C(6)H(7) was at 18 207 cm(-1). From measurements of the dispersed fluorescence spectra and ab initio calculations, the frequencies of several vibrational modes in both the ground and excited states of c-C(6)H(7) were determined: nu(5)(C-H in-plane bend)=1571, nu(8)(C-H in-plane bend)=1174, nu(10)(C-C-C in-plane bend)=981, nu(12)(C-C-C in-plane bend)=559, nu(16)(C-C-C out-of-plane bend)=375, and nu(33)(C-C-C in-plane bend)=600 cm(-1) for the ground state and nu(8)=1118, nu(10)=967, nu(12)=502, nu(16)=172, and nu(33)=536 cm(-1) for the excited states.

Effect of the rate of temperature increase on water quality during heating in electromagnetic- and gas-heated pans.

More rapid increases in the pH value and hardness during electromagnetic heating of a pan of water were observed than when the pan was heated by LNG or LPG. The water quality changed universally in several tap water samples across Japan. This quality change was closely correlated with the rate of temperature increase, irrespective of heating by electromagnetic induction, LNG or LPG.

Polyvinyl alcohol as a useful indicator on iodometry. (II): Temperature dependence of iodine recovery and the correction method of iodine concentration in the lower detection limit region.

In an iodometric titration method for iodine (or chlorine) analysis, the percent recovery of iodine (or chlorine) decreases in the low concentration region and at the relatively higher temperature range. We have shown that the percent recovery vs. concentration curve can be expressed by a simple empirical formula. The empirical formula contains parameters that depend on temperature and those parameters were obtained as a function of temperature. The empirical formula can be used as a correction function for experimental iodine (or chlorine) concentrations. By applying the correction function with the parameters to the experimentally obtained concentrations, we can estimate the reliable concentration in the low concentration region. Estimated concentrations were within 10% (as RSD) of the exact values after the correction in the range of 0.4 mg I2 L(-1) ([triple bond] ca. 0.1 mg as Cl2 L9-1)) - 4.4 mg I2 L(-1) ([triple bond] ca. 1.2 mg as Cl2 L(-1)) in the temperature range of 0 to 30 degrees C.