Spectroscopic and optical characterization of porphyrin chromophores incorporated into ultrathin polyimide films

Polyamic acid (PAA) containing free-base porphyrin and zinc(II) porphyrin chromophores was synthesized by copolymerization of diphenylether-type tetracarboxylic dianhydride and diamines. The monolayer of the alkylamine salts of PAA (PAASs) at the air/water interface was deposited on solid substrates by the Langmuir-Blodgett (LB) technique. The PAAS LB films thus obtained were converted to polyimide (PI) LB films by chemical treatment. The fluorescence of porphyrin moieties in the PI LB film was observed, because of the weak electron-accepting properties of the diphenylether unit. Therefore, the photophysically important processes, such as photoinduced electron transfer, excitation energy transfer, and excitation energy migration could be investigated in relation to the layered nanostructures of the ultrathin PI films. The fluorescence spectrum suggested that the aggregation of porphyrin moieties in the PI LB films was effectively prevented by the use of polymeric films. The surface plasmon (SP) measurement showed that the thickness of the monolayers was 0.9-1.0 nm for PAAS films and 0.32-0.40 nm on average for PI LB films. The absorption dichroism of the Soret band of porphyrin indicated that porphyrin moieties in the PAAS and PI LB films are oriented in parallel with the substrate. These results showed that the orientation and the spatial distribution of porphyrin units can be efficiently regulated in the PI LB films in a nanometer dimension.     

Reaction of azulenes with 1-trifluoromethanesulfonylpyridinium trifluoromethanesulfonate (TPT) and synthesis of the parent azulene

2-Azulenyl trifluoromethanesulfonate was prepared by the reaction of 2-hydroxyazulene with trifluoromethanesulfonic anhydride in the presence of triethylamine as a base. Under the use of pyridine, 1-trifluoromethanesulfonylpyridinium trifluoromethanesulfonate further reacted with 2-azulenyl trifluoromethanesulfonate to give 1-(1-trifluoromethanesulfonyl-1,4-dihydropyridin-4-yl)azulenyl trifluoromethanesulfonate. Moreover, we found that azulenes also reacted with 1-trifluoromethanesulfonylpyridinium trifluoromethanesulfonate to give 4-(1-azulenyl)-1,4-dihydropyridine derivatives and 6-(1-azulenyl)-1-trifluoromethanesulfonyl-1-aza-hexa-1,3,5-triene depending on the reaction conditions. 2-Azulenyl trifluoromethanesulfonate was converted finally into the parent azulene in excellent yield by palladium-catalyzed reduction using formic acid as a reducing reagent.     

Preparation and examination of calcium ion-selective electrodes for flow analysis

The preparation of calcium ion-selective electrodes based on known alkylphenylphosphate exchangers or on the ETH 1001 ionophore, and their use in a flow-through cell in a flow-injection system for the determination of calcium are described. The response and lifetime of the electrodes and the effects of magnesium and sodium ions on the determination of 10^?3?10^?5 M calcium are examined in detail. The ionophore electrode is shown to be most satisfactory.     

Simultaneous determination of ingredients in an ointment by hydrophobic interaction electrokinetic chromatography

Hydrophobic interaction electrokinetic chromatography was used to simultaneously determine seven active ingredients (diphenhydramine hydrochloride, dibucaine hydrochloride, chlorhexidine hydrochloride, phenylephrine hydrochloride, hydrocortisone acetate, allantoin and tocopherol acetate) in an ointment. Not only hydrophobic but also ionic compounds were successfully separated by use of a separation solution composed of acetonitrile-water (80:20, v/v), tetradecylammonium salt and ammonium chloride. The migration behavior of the hydrophobic compound depended on tetradecylammonium concentration, while that of the ionic compounds depended on ammonium chloride concentration. An addition of triethylamine to the separation solution markedly improved the reproducibility of the peak areas of cations with a relative standard deviation (RSD) of less than 1.7% (n=6). The established method was validated and confirmed to be applicable to the determination of the active ingredients in a commercial ointment. Sample preparation was performed by liquid-liquid extraction and no interference from the formulation excipients was observed. Good linearities were obtained, with correlation coefficients above 0.999. Recoveries and precisions ranged from 98.0 to 100.8%, and from 0.4 to 2.9% RSD, respectively. These results suggest that hydrophobic interaction electrokinetic chromatography can be used for the determination of ionic compounds as well as hydrophobic compounds in ointment.     

ENHANCEMENT OF PORPHYRIN-PHOTOSENSITIZATION OF YEAST CELLS BY ETHANOL

Abstract In porphyrin photosensitization, the localization of porphyrin in the cell and the sensitizing activity have been of recent concern. Hydrophobic porphyrins are usually in a highly aggregated state in aqueous systems. This study was designed to see whether the change in the polarity of the environment by adding ethanol could modify the sensitizing effects of porphyrins using a fermentable (alcohol tolerant) yeast ( Saccharomyces cerevisiae ) cells. The results showed that (1) the addition of ethanol (˜15%) to the aqueous suspension remarkably increased inactivation and cell membrane damage both in the hematoporphyrin (HP) and protoporphyrin (PP) photosensitizations, and (2) a sharp induction of genetic changes occurred concomitantly both in HP and PP sensitized cells in the presence of ethanol. In view of the fact that the addition of ethanol modified the absorption spectra and fluorescence intensity of porphyrins in favor of deaggregation, these results may be interpreted to mean that deaggregation of porphyrins promoted by ethanol enhanced their solubility in the lipophilic environment of the cell membrane and even further inside, thereby increasing the sensitizing activities.     

The fluorescence excitation spectrum of aniline in a supersonic free jet: Double minimum potential for the inversion vibration in the excited state

The fluorescence excitation spectrum of the first singlet transition of aniline in a supersonic free jet has been measured. Vibronic transitions involving the inversion vibration of the NH₂ group in the excited state have been observed. The double minimum potential function in the excited state has been determined from the observed vibrational levels.     

Experimental and theoretical studies on the conjugation of the phosphorus-carbon double bond with a cyclopropyl group

X-ray structural analysis for (Z)-2-cyclopropyl-1-(2,4,6-tri-tert-butylphenyl)-1-phosphaethene (2) was performed to confirm that the cyclopropyl group largely interacts with the P[double bond]C group compared with its carbon analogue, vinylcyclopropane (1). Absorption spectrum and redox properties of 2 were also studied to prove the conjugation. Theoretical investigation for nonsubstituted derivatives (4) indicated conjugative interaction between the P[double bond]C and cyclopropyl groups and revealed the physicochemical similarities between the P=C and C[double bond]C.     

Variation of free volume size and content of shape memory polymer — Polyurethane — Upon temperature studied by positron annihilation lifetime techniques and infrared spectroscopy

Positron annihilation lifetime measurement and Fourier transform infrared spectrometry were applied to the study of temperature dependencies of free volume parameters and hydrogen bonds in segmented polyurethane, specially fabricated as a shape memory polymer. The variation of free volumes in amorphous region were correlated to that of hydrogen bonding and the shape memory mechanism of polyurethane is elucidated from a microscopic point of view. The relationship between free volume contents and the formation of hydrogen bonds significantly suggests that the shape memory occurs due to the configurational recovery of the microscopic regulation around urethane bundles of hard segment and consequent restoration of soft-segment in polyurethane.     

Thermal cis–trans isomerization and decomposition of polyacetylene

Thermal cis-trans isomerization and decomposition of polyacetylene film prepared with a Ti(OC₄H₉)₄–Al(C₂H₅)₃ (Al/Ti = 4) system were investigated under inert gas or in vacuum by means of thermal analysis and infrared spectroscopy. Thermograms of differential thermal analysis of cis-polyacetylene revealed the existence of two exothermic peaks at 145 and 325°C and one endothermic peak at 420°C which were assigned to cis-trans isomerization, hydrogen migration accompanied with crosslinking reaction, and thermal decomposition, respectively. The isomerization was followed by infrared spectroscopy over the temperature range 75–115°C. The reaction did not obey simple kinetics. The apparent activation energy for the cis-trans isomerization was 17.0 kcal/mole for the polymer containing 88% cis configuration and increased with increasing trans content up to 38.8 kcal/mole for 80% trans content.