Chemiluminescence of Cypridina Luciferin Analogs. Part 3. MCLA Chemiluminescence with Singlet Oxygen Generated by the Retro-Diels-Alder Reaction of a Naphthalene Endoperoxide

The chemiluminescence of the Cypridina luciferin analog, 2-methyl-6-(p-methoxyphenyl)-3,7-dihydroirnidazo[1,2-a]pyrazin-3-one (MCLA), with O₂ (¹Δ_g) generated by the retro-Diels-Alder reaction of 3-(4′-methyI-l'-naphthyl)-propionic acid endoperoxide was studied in an aqueous solution with pH 7.12 at 37°C. The retro-Diels-Alder reaction occurs with a first-order rate constant of (4.16 ± 0.13) × 10^?4/s to quantitatively yield O₂ (¹Δ_g) and 3-(4′-methyl-l'-naphthyl (-propionic acid. MCLA consumed equimolar amounts of O₂ (¹Δ_g) with a second-order rate constant (6.96 ± 0.27) × 10⁸/M/s to emit light in an aqueous solution with pH 7.12 at 37°C. The chemiluminescence spectrum was identified as the fluorescence spectrum of 2-acetylamino-5-(p-methoxyphenyl)pyrazine (OMCLA), a major chemiluminescence reaction. Chemiluminescence spectra and product yields for MCLA reactions with O₂¹Δ_g, with O₂ (³Σ^?_g) and with superoxide anion radicals are identical, suggesting that all of these reactions occur via a common MCLA-2-hydrope-roxide intermediate formed by a combination of MCLA radicals and superoxide anion radicals. We have established practical use of NEPO as an O₂ (¹Δ_g) source and MCLA as a biological probe for detecting O₂ (¹Δ_g).     

Participation of molecular hydrogen-originated protonic acid sites in acid-catalyzed reactions

The formation of protons from molecular hydrogen was observed by IR of adsorbed pyridine for Pt/SO₄ ²⁻−ZrO₂ when heated in the presence of hydrogen. The promotive effects of hydrogen on skeletal isomerization of alkanes and cumene cracking are rationalized by the formation of protons from hydrogen. The formation of protons and the promotive effects of hydrogen were also observed for other catalysts such as Co.Mo/SiO₂−Al₂O₃ and a physical mixture of Pt/SiO₂ and H-ZSM-5. The concept “molecular hydrogen-originated protonic acid site” is proposed as an important and widely applicable concept in acid-catalyzed reactions.     

Theoretical evidence for enhanced NO dimerization in aromatic hosts: implications for the role of the electrophile (NO)(2) in nitric oxide chemistry

Nitric oxide dimerization in gas phase and aromatic hosts (benzene) has been investigated with ab initio quantum mechanics. Using the (RO)MP2-aug-cc-pVDZ method, the computed bond dissociation energy (ON...NO) and geometry of (NO)2 in the gas phase are consistent with the reported spectroscopic data. A relatively strong interaction (-5.4 kcal/mol) between (NO)2 and benzene indicates that aromatic surrounding enhances the NO dimerization. Calculations on reactions of phosphine and methanethiol with NO and (NO)2 show that the dimer is much more reactive. This explains reactions of NO with phosphines and thiols.     

Investigation of methyl tert-butyl ether levels in river-, ground-, and sewage-waters analyzed using a purge-and-trap interfaced to a gas chromatograph-mass spectrometer

River water collected from 27 sites in 21 rivers, groundwater from 66 sites in 34 cities, and 2 sewage plants in the Niigata Prefecture, Japan (total 301 samples) were analyzed for methyl tert-butyl ether (MTBE) using an improved purge-and-trap-GC-MS method. The amount of MTBE found in water samples from the 27 river sites ranged from 0.003 to 5.3 microg l(-1). MTBE was found in all 27 sites during winter but it was found at only 9 sites and 14 sites, respectively, during the summer. MTBE was found most frequently (in 21 sites) at levels ranging from 0.003 to 0.009 microg l(-1) during February. The highest levels of MTBE were always found in the samples collected from the same site. The amount of MTBE found in sewage water samples ranged from <0.003 to 0.025 microgl(-1). No significant differences were observed between the amounts of MTBE recovered from inflow and outflow waters. Relatively high levels (0.02-0.034 microg l(-1) ) of MTBE were found in January at two sites, which were located on the upper course of the Shinano River. MTBE levels ranged from 0.004 to 0.035 microgl(-l) and from 0.005 to 0.041 microgl(-1) at the mouths of the Shinano River and Agano River, respectively. The levels of MTBE in groundwater collected from 66 sites in 34 cities in Niigata Prefecture ranged from <0.003 to 5.9 microg l(-1).     

Efficient synthesis of 2,6,9-triazabicyclo[3.3.1]nonanes through amine-mediated formal [4+4] reaction of unsaturated imines

Formal [4+4] reaction of the unsaturated benzyl- or allylimines, which is efficiently mediated by primary amine, provides the 2,6,9-triazabicyclo[3.3.1]nonane derivatives. Variously substituted homo- and hetero-coupling products are obtained in good to excellent yields by quite a simple procedure under mild conditions: by mixing the unsaturated aldehydes with the amines at room temperature.     

On-line concentration and fluorescence determination HPLC for polycyclic aromatic hydrocarbons in seawater samples and its application to Japan Sea

An on?line concentration and fluorescence determination HPLC for polycyclic aromatic hydrocarbons (PAHs) in seawater was proposed. An online concentration column packed with octadecyl polyvinyl alcohol polymer, a pump and a column switching valve were introduced in the conventional HPLC with a fluorescence detector. Only 1.0-100?mL seawater sample was introduced into the concentration column at 1.0?mL?min(-1) without any other pretreatment except filtration. Then the trapped PAHs totally flew into the separation column and eluted separately to be detected fluorogenically. The proposed method had good linearity with correlation coefficients (r) ranged from 0.951 to 0.998, and limits of detection ranged from 0.002 to 0.50?ng?L(-1) for 15 PAHs as 100?mL seawater was loaded. The sensitivity of the method was 10 to 100 times higher than those reported by other works. The proposed method was applied to the determination of PAHs in the seawater samples collected in the Japan Sea with satisfactory results and to check the present benzo[a]pyrene concentration at the beaches in Noto peninsula, Japan polluted with C-heavy oil spilled from the tanker in 1997.     

Micropatterning of Sol-Gel Derived Thin Films Using Hydrophobic-Hydrophilic Patterned Surface

Formation process of convexly shaped oxide micropatterns using hydrophobic-hydrophilic patterned surface has been examined, and this technique was applied to several oxide thin films such as SnO₂, ZrO₂, TiO₂ and Al₂O₃. Hydrophobic-hydrophilic patterned surfaces were prepared on glass substrates by selective UV irradiation through a photomask on double-layered films of a very thin TiO₂ gel film as the underlayer and a hydrolyzed fluoroalkyltrimethoxysilane layer as the top layer. Precursor solutions were then spin-coated on the hydrophobic-hydrophilic patterns, and the coated substrates were dried at room temperature. The micropatterns of oxides were very difficult to be formed on the hydrophobic-hydrophilic patterned surfaces from metal-alkoxides as a precursor solution, but convexly shaped micropatterns were formed on the hydrophilic regions of the pattern when metal chlorides or oxychlorides were used as starting materials. This patterning technique potentially has a wide variety of applications such as fabrication of micro-optical components and finely patterned transparent electrodes.     

Derivatization of a tris-oxazole using Pd-catalyzed coupling reactions of a 5-bromooxazole moiety

Modification at the C5 position of an oxazole ring contained in a 2,4-concatenated tris-oxazole by Pd-catalyzed coupling reactions was performed. Novel Pd-catalyzed amination and alkoxylation of a 5-bromooxazole derivative as well as Suzuki-Miyaura coupling and Migita-Stille coupling have been demonstrated. A wide variety of functional groups, including aryl, heteroaryl, primary and secondary amines, and phenol, were introduced in the 5-bromooxazole moiety in moderate to excellent yields using Pd(OAc)₂/S-PHOS or Pd(OAc)₂/X-PHOS as a catalyst.     

Two-color sum frequency generation study of poly(9,9-dioctylfluorene)/electrode interfaces

The air/PFO and the buried electrode/PFO interfaces have been investigated by two-color SFG spectroscopy. Due to the interface confinement effects, the planes of PFO rings are nearly parallel to the surface plane, and the optical band gaps become smaller at the interfaces than those of the bulk.     

Synthesis, structure, and bonding properties of 5-carbaphosphatranes: a new class of main group atrane

1-Hydro-5-carbaphosphatrane (1) and 1-methyl-5-carbaphosphatrane (2), the first 5-carbon analogues of phosphatranes, were synthesized by a demethylation reaction of cyclic phosphinate 3. X-ray analysis revealed that 1 has a typical trigonal bipyramidal structure with hydrogen and carbon atoms at the apical position and three oxygen atoms at the equatorial positions, indicating that 1 is a phosphorane in the perfectly "anti-apicophilic" arrangement. Apical P-C and P-H bond lengths were 1.921(2) and 1.38(2) A, respectively. The (1)J(PH) value of 1 and the (1)J(PC)(P-CH(3)) value of 2 were 852 and 215 Hz, respectively, which are extraordinarily large for the apical coupling constants of phosphoranes, but close to those of the reported phosphatranes with a 5-nitrogen atom. IR and Raman spectra are also reported. Force constant calculations indicate the transannular bond in carbaphosphatrane is 3 times stronger than in silatrane, due to its covalent character.