Haruo Inoue

The role of intersystem crossing in the deactivation of the singlet excited aminofluorenones

Solvent n and substituent effects on the competition between internal conversion and triplet formation were studied systematically for aminofluorenones and their N-methylated derivatives. Intersystem crossing (ISC) n was found to be the dominant process for the singlet excited 1-amino- and 1-methylaminofluorenone in all n solvents. The short fluorescence decay time of these compounds does not originate from intramolecular n hydrogen bonding induced internal conversion but it is due to the fast triplet formation. Rather slow (kISC⩽4.8 × 107 s−1) and solvent insensitive intersystem crossing characterizes the photophysical behavior of 2-, n 3- and 4-aminofluorenones but their internal conversion rate strongly increases with solvent polarity. The change n of the internal conversion rate constants with molecular structure and solvent can be rationalized in terms n of the energy gap law.

Novel synthesis of hexaaryl[3]radialenes via dibromo[3]dendralenes

Abstract We report here an efficient route to the synthesis of highly fluorescent hexaaryl[3]radialenes using the oligomerization of ate-type copper carbenoids, followed by cyclization with hexamethylditin and Pd(PPh3)4; the structures of the [3]dendralene and hexaaryl[3]radialenes were determined by X-ray crystallographic analysis.

Enhanced aggregation of Tin(IV)porphyrins in a polyfluorinated surfactant-clay hybrid environment

Abstract Tetra-(4-sulfonatophenyl)porphyrinatotin(IV) aggregated efficiently in a clay (saponite) layer intercalated with a polyfluorinated surfactant, but no aggregation was observed in a hydrocarbon type surfactant-clay hybrid environment. Germanium(IV) porphyrins remained as monomers even in the polyfluorinated environment.

Factors controlling the deactivation induced by hydrogen-bonding interaction: Steric and electronic effects on dual anisotropic relaxation processes

The factors controlling deactivation from the intramolecular charge transfer excited states of aminoanthraquinones and aminofluorenones induced through intermolecular hydrogen-bonding interactions with alcohols such as p-substituted benzyl alcohols and bulky alcohols were investigated by steady-state and time-resolved fluorescence spectroscopy. The ratios of the Stern–Volmer constants for the fluorescence quenching by the alcohols to the contact molecular surface area of the hydroxy hydrogen were correlated well with the charge density of the hydroxy hydrogen of the alcohols. The rate constant of the forward process which forms a relaxed hydrogen-bonded complex in the excited state was revealed to depend on the contact molecular surface area of the hydroxy hydrogen, whereas the reverse process was mainly controlled by electronic effects which stabilize the relaxed hydrogen-bonded complex.

Surface polyfluorinated cationic vesicles

Three novel polyfluorinated cationic surfactants having a short perfluoroacyl group and double long alkyl chains, and three corresponding hydrocarbon analogues were synthesized. All of the surfactants formed small unilamellar vesicles in water upon sonication. The temperature conditions for the sonication were carefully determined by confirming that the DSC curve had a reproducible single phase transition peak. The TEM images indicated that the size of the polyfluorinated vesicles was in the range of 56–89 nm. The NMR relaxation study upon the addition of paramagnetic Mn2+ ions to the bulk water phase showed that the terminal trifluoromethyl group of the short acylamide chain in the surfactants faced directly to the bulk water phase; the vesicle had a unique micro-structure with the perfluoroalkyl group extending its arm straightforwardly to the water phase. The vesicles were named ‘surface polyfluorinated vesicles’. The local oxygen concentrations surrounding each fluorine nucleus and proton of the surfactants within the vesicles were estimated by observing the longitudinal relaxation time under nitrogen and oxygen atmospheres. Oxygen was enriched in the microenvironment surrounding the long alkyl chain and perfluoralkyl group, while the N-methyl group had a low oxygen concentration around it. The micro-distribution of water within the vesicle was discussed by the estimated local concentration of oxygen. The vesicles were thought to be stabilized by the channel-like water connecting the bulk water phase with the hydrated water of the N-methyl groups inside the vesicles. The surface polyfluorinated layer exhibited a substantial protective effect against the oxidative attack of hydroxyl radical generated in the bulk phase water.

Silylated poly(4-hydroxystyrene)s as negative electron beam resists

Silylated poly(4-hydroxystyrene)s and radical polymerized 4-tert-butyldimethylsilyloxystyrene (TBDMSOSt) were examined as electron beam resists. Commercial poly(4-hydroxystyrene) (PHS) with Mw = 1.69 × 104 and Mw/Mn = 5.41 was silylated with 1-(trimethylsilyl)imidazole and tert-butylchlorodimethylsilane. Both silylation reactions proceeded quantitatively to afford trimethylsilylated PHS with Mw = 3.93 × 104 and Mw/Mn = 4.91, and tert-butyldimethylsilylated PHS with Mw = 4.08 × 104 and Mw/Mn = 3.81. These 2 silyl ether polymers acted as a negative working resist to electron beam (EB) exposure. Sensitivity and contrast of tert- butyldimethylsilylated PHS were not affected by prebake temperature around its Tg of 97°C, while those of PHS were dependent on prebake temperature around its Tg of 160°C. At a prebake temperature of 125°C, the sensitivity parameter and the contrast γ value were obtained as follows: 3.93 × 10−4 C cm−2 and 0.91 for PHS; 1.49 × 10−4 C cm−2 and 1.06 for trimethylsilylated PHS; 1.84 × 10−4 C cm−2 and 1.44 for tert-butyldimethylsilylated PHS. The silylation procedures obviously improved the sensitivity of PHS. TBDMSOSt was polymerized in bulk at 60°C with 2,2′-azobisisobutyronitrile (AIBN) as an initiator. The resultant poly(TBDMSOSt) possessed Mw = 3.01 × 105 and Mw/Mn = 1.92 and exhibited a sensitivity of 1.60 × 10−5 C cm−2 and a γ value of 1.47. More than 10 times enhancement of sensitivity was observed compared with tert-butyldimethylsilylated PHS. Such a high sensitivity is probably due to the high molecular weight of the bulk polymerized material. Poly(TBDMSOSt) resolved an isolated line of 0.20 μm width and 0.5 μm line and space patterns.

Desulfonylation of poly(4-hydroxystyrene sulfone) by Vapor phase silylation

Vapor phase silylation of poly(4-hydroxystyrene sulfone) (PHOSS) film was carried out with (trimethylsilyl)dimethylamine (TMSDMA) as a silylation reagent. Infrared spectroscopy was used to follow the silylation. Phenolic hydroxyl groups were trimethylsilylated, but desulfonylation of PHOSS was greatly enhanced simultaneously. The reaction rates were investigated at reaction temperatures of 50, 60, and 70°C. The rate of silylation increased with increasing reaction temperature. However, the rate of desulfonylation was very fast in the presence of TMSDMA and was virtually invariant with reaction temperature. It was confirmed that trimethylsilylation in the polymer side chain of PHOSS enhanced desulfonylation in the main chain. Trimethylsilylation might be expected to lower the ceiling temperature of the polymer.