PHOTOVOLTAGE AND PHOTOCURRENT AT TETRAPHENYLPORPHYRIN AND ZINC TETRAPHENYLPORPHYRIN ELECTRODES IN ACIDIC SOLUTIONS

Abstract— Photoelectrochemical properties of tetraphenylporphyrin and zinc tetraphenylporphyrin spread on a platinum plate were investigated in acidic solutions containing a variety of electroactive species. It was found that the photovoltage measured in 0.5 M sulfuric acid solutions depended strongly on the redox potential of the electroactive species; species having a redox potential of around 1.0 V vs NHE (such as oxygen and dichromate ions) generated the largest photovoltage. A similar dependency was also observed in the photocurrent, although a little ambiguous. These phenomena are discussed from a point of semiconductor electrochemistry. The magnitude of the photocurrent was found to be influenced by solution pH, suggesting that protonation of the porphyrin film surface plays an important role in the charge transfer process.     

Chlorotrimethylsilane promoted asymmetric Michael reaction of chiral enamines of α-alkyl β-keto esters

By the promotion of chlorotrimethylsilane, asymmetric Michael reaction of the chiral enamines (2) of α-alkyl β-keto esters (1) with methyl vinyl ketone and ethyl acrylate proceeded to afford, after hydrolysis, either enantiomer of the corresponding adducts (4) in a good enantioselectivity.     

Intramolecular Substitution Reaction of Alkylidene‐Lithium Carbenoids: Regioselective Synthesis of Indenes

Intramolecular substitution reaction of geminal dibromo alkenes proceeds to afford indenes, dihydronaphthalenes, dihydrofurans, and dihydropyran via in situ generated lithium alkylidene carbenoids, which have a carbon or oxygen nucleophilic moiety. This reaction provides a regioselective method for the preparation of polysubstituted indenes.     

A Systematic Investigation on Leaky Characteristics for NRD Guide with Arbitrary Profile of Cross-Section

The leaky characteristics of the NRD guide with arbitarary profile of cross section are systematically studied by a method which combines staircase approximation with multimode network theory and mode-matching procedure. Emphasis is laid on the investigation of the effect of the different profile dimensions on the leakage characteristics of the NRD guide. Extensive numerical results are given to establish useful guidelines for the design of some new types of NRD guide leaky wave antennas.     

Synthesis and properties of new halogen‐substituted polyamides from 5‐halo‐m‐phenylenediamines and both aliphatic and aromatic dicarboxylic acids

New halogen‐substituted aromatic–aliphatic and wholly aromatic polyamides with high inherent viscosities were synthesized by the direct polycondensation of 5‐halo‐m‐phenylenediamines, where the halogens were Cl, Br, and I, with both aliphatic and aromatic dicarboxylic acids in N‐methyl‐2‐pyrrolidone with a mixture of triphenyl phosphite and pyridine as a condensing agent. The solubility of the halogen‐substituted polyamides was much higher than that of the parent polyamides derived from m‐phenylenediamine. The glass‐transition temperatures of the substituted aromatic–aliphatic polyamides increased in the order Cl < Br < I, whereas the temperatures of 10% weight loss in air decreased in the reverse order. The limiting oxygen index values, as an indication of flammability, increased for the substituted aromatic–aliphatic polyamides in the order Cl < Br < I. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 3911–3918, 2000     

Lipophilic aminimides possessing an additional ligating group as extractants for heavy metal cations

The title compounds were prepared in good yields by Slagel's method. All compounds obtained were used as agents for liquid-liquid extraction. They showed high affinity for certain heavy metal cations and their extractability depended to a great extent on the ligand structure. This dependence is believed to be due to the chelation of the metal cations between the imino nitrogens and the additional ligating site.     

Enantiomer separation by reversed-phase liquid chromatography with novel hydrophobic phases composed of chiral cationic surfactants

This paper describes enantiomer separation using four kinds of chiral stationary phases (CSPs) where quaternary ammonium surfactants containing L-valine diamide moieties into long alkyl chains were bound to silicagel supports by reversed phase liquid chromatography. Our aim was to examine hydrogen bonding association of the chiral moiety in hydrophobic phase brought about by aggregation of the micelle-forming surfactants on the surface. The following CSPs were thus derived from the vinyl-terminated chiral surfactants via hydrosilylation: CSP 1 from N-[3-(10-undecenoyl-L-valylamino)propyl]-N,N,N-trimethylammonium bromide, CSP 2 from N-[6-(10-undecenoyl-L-valylamino)hexyl]-N,N,N-trimethyl-ammonium bromide, CSP 3 from N-[3-(10-undecenoyl-L-valylamino)propyl]-N-octadecanyl-N,N-dimethyl-ammonium bromide and CSP 4 from N-[6-(10-undecenoyl-L-valylamino)hexyl]-N-octadecanyl-N,N-dimethylammonium bromide. The degree of hydrophobicity in the interfacial phase was observed by measuring pyrene fluorescence in aqueous media including an organic modifier. Retention of racemic N-acylleucine isopropyl esters was highest in CSP 4, followed by 3, 2, and 1. Largest alpha values toward enantiomer separation were observed for CSP 4 where the chiral moieties were kept through a hexamethylene unit apart from the polar head groups and to which another long alkyl chain was attached, as compared with those for CSP 4. In CSP 4, the chiral moiety to interact with enantiomeric solutes should be buried into the interfacial phase deeply in more extent than CSP 3. In a similar manner, CSP 2 has more effective for enantiomer separation than CSP 1. The interfacial phase of these CSPs was easily exposed to the bulk phase because of the affinity between the bulk phase and the polar head groups as well as their electrostatic repulsion. However, degree of the enantiomer separation can be controlled by the depth of the chiral moiety in the hydrophobic interfacial phase.     

Rhodium-catalyzed reaction of thiols with polychloroalkanes in the presence of triethylamine

[reaction: see text] RhCl(PPh(3))(3) catalyzes a reaction of thiols with polychloroalkanes in the presence of triethylamine. This reaction serves as a convenient new method to produce formaldehyde dithioacetals, ethylenedithioethers, thioformates, and dithiocarbonic esters under mild conditions.