An unusual reaction of α-alkoxyphosphonium salts with Grignard reagents under an O2 atmosphere

An unusual and novel reaction of α-alkoxyphosphonium salts, generated from O,O-acetals and Ph(3)P, with Grignard reagents under an O(2) atmosphere afforded alcohols in moderate to high yields. It was clarified by isotopic labelling experiments that the reaction proceeded via a novel radical pathway.     

Structural Analysis of Triacylglycerols by Using a MALDI-TOF/TOF System with Monoisotopic Precursor Selection

A new MALDI-TOF/TOF system with monoisotopic precursor selection was applied to the analysis of triacylglycerols in an olive oil sample. Monoisotopic precursor selection made it possible to obtain product-ion mass spectra without interference from species that differed by a single double bond. Complete structure determination of all triacylglycerols, including structural isomers, was made possible by interpreting the charge-remote fragmentation resulting from high-energy collision-induced dissociation (CID) of the sodiated triacylglycerols.      

Facile Synthesis of Hydroxy‐Modified MOF‐5 for Improving the Adsorption Capacity of Hydrogen by Lithium Doping

A facile synthesis of partially hydroxy‐modified MOF‐5 and its improved H₂‐adsorption capacity by lithium doping are reported. The reaction of Zn(NO₃)₂ ? 6 H₂O with a mixture of terephthalic acid (H₂BDC) and 2‐hydroxyterephthalic acid (H₂BDC‐OH) in DMF gave hydroxy‐modified MOF‐5 (MOF‐5‐OH‐x), in which the molar fraction (x) of BDC‐OH^2? was up to 0.54 of the whole ligand. The MOF‐5‐OH‐x frameworks had high BET surface areas (about 3300 m² g^?1), which were comparable to that of MOF‐5. We suggest that the MOF‐5‐OH‐x frameworks are formed by the secondary growth of BDC^2?‐rich MOF‐5 seed crystals, which are nucleated during the early stage of the reaction. Subsequent Li doping into MOF‐5‐OH‐x results in increased H₂ uptake at 77 K and 0.1 MPa from 1.23 to 1.39 wt. % and an increased isosteric heat of H₂ adsorption from 5.1–4.2 kJ mol^?1 to 5.5–4.4 kJ mol^?1.     

Electrical properties and electronic states of molecular conductors based on unsymmetrical organometallic-dithiolene gold(III) complexes

The electronic properties of cation radical salts derived from organometallic mixed-ligand complexes [(ppy)Au(S-S)](ppy- = C-dehydro-2-phenylpyridine(-); S-S(2-) = dithiolene ligand) with Au(III)-C sigma-bond were investigated. A 2:1 salt complex [(ppy)Au(C8H4S8)]2[PF6] (C8H4S8(2-) = 2-((4,5-ethylenedithio)-1,3-dithiole-2-ylidene)-1,3-dithiole-4,5-dithiolate(2-)) exhibited semiconductive behavior under ambient pressure (rho rt = 2.6 Omega cm, Ea = 0.03 eV). Magnetic measurements show that it is a Mott insulator close to the metal-insulator boundary. Raman and infrared spectra have revealed that the complex has a quasi-one-dimensional dimeric structure consisting of uniformly charged donor molecules. The complex exhibits metallic behavior at pressures above 0.8 GPa. In contrast, a similar compound [(ppy)Au(C8H4S6O2)]2[BF4] (C8H4S6O2(2-) = 2-((4,5-ethylenedioxy)-1,3-dithiole-2-ylidene)-1,3-dithiole-4,5-dithiolate(2-)) is a band insulator.     

H2O2-reactivity of copper(II) complexes supported by tris[(pyridin-2-yl)methyl]amine ligands with 6-phenyl substituents

The structure and H(2)O(2)-reactivity of a series of copper(II) complexes supported by tris[(pyridin-2-yl)methyl]amine (TPA) derivatives having a phenyl group at the 6-position of pyridine donor group(s) [(6-phenylpyridin-2-yl)methyl]bis[(pyridin-2-yl)methyl]amine (Ph(1)TPA), bis[(6-phenylpyridin-2-yl)methyl][(pyridin-2-yl)methyl]amine (Ph(2)TPA), and tris[(6-phenylpyridin-2-yl)methyl]amine (Ph(3)TPA) have systematically been examined to get insights into the aromatic substituent (6-Ph) effects on the coordination chemistry of TPA ligand system. The X-ray crystallographic analyses have revealed that [Cu(II)(TPA)(CH(3)CN)](ClO(4))(2) (CuTPA) and [Cu(II)(Ph(3)TPA)(CH(3)CN)](ClO(4))(2) (3) exhibit a trigonal bipyramidal structure, whereas [Cu(II)(Ph(1)TPA)(CH(3)CN)](ClO(4))(2) (1) shows a slightly distorted square pyramidal structure and [Cu(II)(Ph(2)TPA)(CH(3)CN)](ClO(4))(2) (2) has an intermediate structure between trigonal bipyramidal and square pyramidal. On the other hand, the UV-vis and ESR data have suggested that all the copper(II) complexes have a similar trigonal bipyramidal structure in solution. The redox potentials of CuTPA, 1, 2, and 3 have been determined as E(1/2) = -0.34, -0.28, -0.16, and -0.04 mV vs Ag/AgNO(3), respectively, demonstrating that introduction of each 6-Ph group causes positive shift of E(1/2) about 0.1 V. Notable difference in H(2)O(2)-reactivity has been found among the copper(II) complexes. Namely, CuTPA and 1 afforded mononuclear copper(II)-hydroperoxo complexes CuTPA-OOH and 1-OOH, respectively, whereas complex 2 provided bis(mu-oxo)dicopper(III) complex 2-oxo. On the other hand, copper(II) complex 3 was reduced to the corresponding copper(I) complex 3(red). On the basis of the H(2)O(2)-reactivity together with the X-ray structures and the redox potentials of the copper(II) complexes, the substituent effects of 6-Ph are discussed in detail.     

High-sensitivity simultaneous analysis of ubiquinol-10 and ubiquinone-10 in human plasma

A method to determine ubiquinol-10 and ubiquinone-10 in human serum was developed by using high-performance liquid chromatography consisting of a semi-microcolumn switching system and an electrochemical detector (ECD), which requires minimized sample pre-treatments. A linear dynamic range was obtained from 1.0 to 5000 ng/mL, and recovery values of 89-105% were observed in a low-concentration region of 10-50 ng/mL. In a long operation test, a good precision was maintained during 5100 runs without any maintenance on ECD or columns. In addition, retention behaviors of other ubiquinone homologues were examined.     

Control of photophysical properties and photoreactions of aromatic imides by use of intermolecular hydrogen bonding

The effect of addition of alcohols on the photophysical properties and the photoreactions of N-methylphthalimide (1), N-methyl-1,8-, -2,3-, and -1,2-naphthalimide (2-4), and N-methyl-9,10-phenanthrenedicarboximide (5) has been investigated. The UV and IR spectra of aromatic imides 1-5 showed the presence of the intermolecular hydrogen bonding between the carbonyl group of the aromatic imides and the alcohols in less polar solvents. The equilibrium constants K for the hydrogen bonding were determined by the UV spectra. The fluorescence intensities of 2 and 1 were found to be remarkably and moderately enhanced by the addition of alcohols, respectively, though those of 3-5 were little enhanced by the addition of alcohols. On the other hand, photochemical cyclobutane formation of 2 with styrene (6) was found to be enhanced by the addition of 2,2,2-trifluoroethanol in benzene. Enhancement of the fluorescence quantum yields Phi(f) and the photoreaction of 2 by the hydrogen bond formation was explained by the decrease of the efficiency of the intersystem crossing from (1)(pi pi*) to (3)(n pi*), whose energy was increased by the hydrogen bonding.     

Highly sensitive spectrophotometric determination of cationic surfactants in ground waters as their Cu(II)-TPPS aggregates preceded by solid-phase fractionation

A highly sensitive spectrophotometric determination of cationic surfactants in ground waters was established by forming their Cu(II)-TPPS aggregates, preceded by solid-phase extraction with an SCX cartridge. Cationic surfactants (CSs) were quantitatively trapped and isolated by the SCX solid phase. The use of Cu(II)-TPPS anionic chromophore could reduce the interference by unintentional metal ions coexisting in surrounding waters. The method was very sensitive in the determination of CSs less than 10⁻⁵ M levels with acceptable recovery and calibration data. The colorimetric sensitivity was very dependent on the alkyl-chain length of the surfactants, and a CS having 23 carbon atoms gave the highest sensitivity. Overall recoveries were 95-97% with R.S.Ds. less than 3% in the cases over 10⁻⁶ M levels. In the cases in 10⁻⁷ M levels, however, a portion of the analyte would be adsorbed by reservoir walls, which could seriously affect the trace determination. The preliminary addition of 4,4′-bipyridyl into the sample solution was effective in decreasing such unintentional analyte losses, leading up to 73% recovery. The developed method was applied to the analysis of river water at ppb levels of CSs with a fractional concentration through a SCX solid phase subjected by 500-mL aliquots of sample.     

Reaction of beta-diketiminate copper(II) complexes and Na2S2

Reaction of beta-diketiminate copper(II) complexes and Na2S2 resulted in formation of (mu-eta2:eta2-disulfido)dicopper(II) complexes (adduct formation) or beta-diketiminate copper(I) complexes (reduction of copper(II)) depending on the substituents of the supporting ligands. In the case of sterically less demanding ligands, adduct formation occurred to provide the (mu-eta2:eta2-disulfido)dicopper(II) complexes, whereas reduction of copper(II) took place to give the corresponding copper(I) complexes with sterically more demanding beta-diketiminate ligands. Spectroscopic examinations of the reactions at low temperature using UV-vis and ESR as well as kinetic analysis have suggested that a 1 : 1 adduct LCuII-S-SNa with an end-on binding mode is initially formed as a common intermediate, from which different reaction pathways exist depending on the steric environment of the metal-coordination sphere provided by the ligands. Thus, with the sterically less demanding ligands, rearrangement of the disulfide adduct from end-on to side-on followed by self-dimerisation occurs to give the (mu-eta2:eta2-disulfido)dicopper(II) complexes, whereas such an intramolecular rearrangement of the disulfide co-ligand does not take place with the sterically more demanding ligands. In this case, homolytic cleavage of the CuII-S bond occurs to give the reduced copper(I) product. The steric effects of the supporting ligands have been discussed on the basis of detailed analysis of the crystal structures of the copper(II) starting materials.