Hydrogen-bond Networks Involving Protonated Bicapped-Keggin Tetradecavanadophosphate Anions

Tetraphenylphosphonium salts of protonated tetradecavanadophosphate (PV₁₄) anions, [(C₆H₅)₄P]₄H₅PV₁₄O₄₂·5H₂O (1) and [(C₆H₅)₄P]₂H₇PV₁₄O₄₂·6H₂O (2), have been synthesized and their crystal structures have been determined. Compound 1 crystallizes in triclinic, P1 with a=12.7866(1), b=15.5261(2), c=16.0730(3) ?, α=109.358(1), β=98.411(1), γ=110.040(1)°. Synchrotron radiation X-ray diffraction revealed that compound 2 crystallizes in monoclinic, P2₁/c with a=16.821(1), b=25.163(2), c=18.817(1) ?, β=109.992(2)°. In compound 1, the PV₁₄ anions are linked into a one-dimensional chain structure by water molecules of crystallization. In compound 2, hydrogen bonds directly link PV₁₄ anions into a zigzag chain, which are then woven into a three-dimensional network by hydrogen bonds bridged by water molecules.Dedicated to Professor Michael T. Pope on the occasion of his retirement, in recognition of his outstanding contributions to the polyoxometalate chemistry.     

Determination of docosahexaenoic acid and n-3 fatty acids in refined fish oils by 1H-NMR spectroscopy: IUPAC interlaboratory study

A high-resolution proton nuclear magnetic resonance (NMR) method for determining the concentration (mg/g) of docosahexaenoic acid (DHA), the molar proportion (mol%) of DHA, and the molar proportion of total n-3 fatty acids in fish oils was validated by an IUPAC interlaboratory study (the Commission VI-6 on Oils, Fats, and Derivatives WG 3/98). Thirteen laboratories from 5 countries tested 6 pairs of blind duplicate fish oils: a refined tuna oil, 2 extracted tuna oils, an extracted bonito oil, an extracted salmon oil, and an extracted sardine oil ranging from 9 to 30 mol% DHA and from 20 to 35 mol% n-3 fatty acids. Before 1 D-proton NMR measurements with 300-500 MHz instruments, oil samples were weighed and diluted with deuterochloroform solution containing ethylene glycol dimethyl ether as internal standard. To achieve precise performance, a detailed procedure for signal area measurement was described in the protocol, and all participants were instructed about the critical importance of following the protocol. Statistical performances with invalid and outlier data removed were as follows: repeatability relative standard deviations (RSDr) ranged from 0.91 to 2.62% and reproducibility relative standard deviation (RSDR) ranged from 1.73 to 4.27% for DHA concentration (mg/g); RSDr ranged from 0.39 to 2.06%, and RSDR ranged from 0.59 to 3.46% for mol% DHA; RSDr ranged from 0.23 to 0.90% and RSDR ranged from 0.85 to 2.01 % for mol% total n-3 fatty acids. The method is expected to be recommended by IUPAC.     

Preparation and Properties of Sol–Gel Thin Film Containing Rhodamine B Derivative with Ethoxy Silano Group on Organic Substrate and its Application to Surface-Treatment Thin Film for Display

A thin film containing rhodamine B derivative with ethoxy silano group was formed on organic film substrate using the sol–gel method. Rhodamine B derivative with a triethoxysilano group, SiO₂ sol and acrylic polymer having a triethoxy group were reacted in alcohol to give a coating solution for film formation, followed to be roll-coated on polyethylene terephthalate (PET) film and heat-treated at 130°C. This thin film consists of inorganic polymer (SiO₂), organic polymer (acrylic resin) and organic dye. These component parts become interconnected through mutual chemical bonding. This thin film has an absorption peak at 578 nm and superb water resistant characteristics (almost no dye elution in 50°C water for 150 min) as a result of chemical bonding between the organic dye and the matrix skeleton. It also has good flexibility. The film can be used as a wavelength-selective absorption film for displays to improve contrast.     

Directly meso-meso linked porphyrin rings: synthesis, characterization, and efficient excitation energy hopping

Directly meso-meso linked porphyrin rings CZ4, CZ6, and CZ8 that respectively comprise four, six, and eight porphyrins have been synthesized in a stepwise manner from a 5,10-diaryl zinc(II) porphyrin building block. Symmetric cyclic structures have been indicated by their very simple (1)H NMR spectra that exhibit only a single set of porphyrin and their absorption spectra that display a characteristic broad nonsplit Soret band around 460 nm. Energy minimized structures calculated at the B3LYP/6-31G* level indicate that a dihedral angle between neighboring porphyrins decreases in order of CZ6 > CZ8 > CZ4, which is consistent with the (1)H NMR data. Photophysical properties of these molecules have been examined by the steady-state absorption, fluorescence, fluorescence lifetime, fluorescence anisotropy decay, and transient absorption measurements. Both the pump-power dependence on the femtosecond transient absorption and the transient absorption anisotropy decay profiles are directly related with the excitation energy migration processes within the porphyrin rings, where the exciton-exciton annihilation time and the polarization anisotropy rise time are well described in terms of the Forster-type incoherent energy hopping model. Consequently, the excitation energy hopping rates have been estimated for CZ4 (119 +/- 2 fs)(-)(1), CZ6 (342 +/- 59 fs)(-)(1), and CZ8 (236 +/- 31 fs)(-)(1), which reflect the magnitude of the electronic coupling between the neighboring porphyrins. Overall, these porphyrin rings serve as a well-defined wheel-shaped light harvesting antenna model in light of very efficient excitation energy hopping along the ring.     

Self-assembly of a lacunary alpha-Keggin undecatungstophosphate into a three-dimensional network linked by s-block cations

The crystal structure of [(CH3)4N]4Na2H[alpha-PW11O39].8H2O has been determined by using the Weissenberg camera at the BL04B2 beamline of SPring-8, revealing that it contains a disorder-free lacunary [alpha-PW11O39]7- anion with one sodium cation embedded into its lacuna that links the oxometalate building blocks into a one-dimensional chain, which is then woven into a three dimensional latticework by another Na+.     

Dynamics of photoinduced surface reactions on semi-conductors studied by a pulsed-laser—dynamic-mass-spectrometer technique

Photoinduced reaction products on semiconductor surfaces were detected time dependently by a pulsed-laser—dynamic-mass-spectrometer technique in an ultrahigh vacuum system. Analysis of the time-resolved curve of the products revealed that the Boltzmann distribution of velocity was realized for the photodesorption of CO₂ and H₂O on ZnO and TiO₂. The local temperature and energy partitioning on the surface are discussed.     

The effect of carbon chain length of the diphosphine ligand on the aurophilic interaction. Synthesis and X-ray structural study for a series of Au(I) compounds with Ph2P-R-PPh2 and S-(CH2)n-py ligands

The effect of the carbon chain-length for Ph₂P-R-PPh₂ (R = -CHCH-, -CH₂-CH₂-, -CH₂-CH₂-CH₂-, and -CH₂-CH₂-CH₂- CH₂-) and S-(CH₂)_n-pyridine ligand (n = 0 to 2) on the aurophilic interaction has been explored systematically. The effect of the N position in x-mercaptopyridine (x = 2 or 4) toward Au(I) center and/or the SR group was also investigated. X-ray structural study was made for 12 new derivatives. The Au-Au distances are below 3.0 Å for 2-S-pyridine derivatives with Ph₂P-CHCH-PPh₂ (t-dpen) and Ph₂P-CH₂-CH₂-PPh₂ (dppe) ligand and the pyridine N atoms come in close contact with the H atoms of these diphosphine carbon chains. A local coplanar conformation is formed between 2-S-pyridine and Au-P-CH groups for these derivatives. The carbon chain lengths are not too consequential on the induction of aurophilicity. Various infinite and/or dimer structures have been revealed from single crystal X-ray analysis for the present series of compounds.     

Systematic synthesis, isolation, and photophysical properties of linear-shaped Re(I) oligomers and polymers with 2-20 units

Systematic synthesis routes have been developed for the linear-shaped rhenium(I) oligomers and polymers bridged with bidentate phosphorus ligands, [Re(N--N)(CO)3-PP-{Re(N--N)(CO)2-PP-}(n)Re(N--N)(CO)3](PF6)(n+2) (N--N = diimine, PP = bidentate phosphine, n = 0-18). These were isolated by size exclusion chromatography (SEC) and identified by (1)H NMR, IR, electrospray ionization Fourier transform mass spectrometry, analytical SEC, and elemental analysis. Crystal structures of [Re(bpy)(CO)3-Ph2PC[triple bond]CPPh2-Re(bpy)(CO)3](PF6)2, [Re(bpy)(CO)3-Ph2PC[triple bond]CPPh2-Re(bpy)(CO)2-Ph2PC[triple bond]CPPh2-Re(bpy)(CO)3](PF6)3 and [Re(bpy)(CO)3-Ph2PC2H4PPh2-{Re(bpy)(CO)2Ph2PC2H4PPh2-}(n)Re(bpy)(CO)3](PF6)(n+2) (bpy = 2,2'-bipyridine, n = 1, 2) were obtained, showing that they have interligand pi-pi interaction between the bpy ligand and the phenyl groups on the phosphorus ligand. All of the oligomers and polymers synthesized were emissive at room temperature in solution. For the dimers, broad emission was observed with a maximum at 523-545 nm, from the (3)MLCT excited-state of the tricarbonyl complex unit, [Re(N--N)(CO)3-PP-]. Emission from the longer oligomers and polymers with > or = 3 Re(I) units was observed at wavelengths 50-60 nm longer than those of the corresponding dimers. This fact and the emission decay results clearly show that energy transfer from the edge unit to the interior unit occurs with a rate constant of (0.9 x 10(8))-(2.5 x 10(8)) s(-1). The efficient energy transfer and the smaller exclusive volume of the longer Re(I) polymers indicated intermolecular aggregation for these polymers in an MeCN solution.     

Highly oxidized ergosterols and isariotin analogs from an entomopathogenic fungus,Gibellula formosana,cultivated in the presence of epigenetic modifying agents

The concomitant addition of a histone deacetylase inhibitor, suberoyl bis-hydroxamic acid, and a DNA methyltransferase inhibitor, RG-108, to the culture medium of Gibellula formosana, an entomopathogenic fungus, induced a significant increase in diversity of secondary metabolites. From the culture media were isolated two new highly oxidized ergosterols, formosterols A (1) and B (2), and five new isariotin analogs, 12′-O-acetylisariotin A (4), 1-epi-isariotin A (5), and isariotins K–M (6–8), together with 22,23-epoxy-3,12,14,16-tetrahydroxyergosta-5,7-dien-11-one (named formosterol C) (3), isariotins A (9), C (10), and E (11), TK-57-164A (12), and beauvericin (13). The NMR spectra, X-ray single crystallographic diffraction, and chemical transformations revealed the structures of the two new formosterols and five new isariotins. The stereochemistry of formosterol C (3) was deduced from its spectroscopic data. The side chains of formosterols A–C (1–3) contained cis-22,23-epoxide, which is rarely present in naturally occurring sterols and triterpenes.     

Crystallization of a Keplerate-type polyoxometalate into a superposed kagome-lattice with huge channels

Crystal structures of two Sr(2+) salts of the Keplerate-type polyoxometalate, [Mo(VI)(72)Mo(V)(60)O(372)(CH(3)COO)(30)(H(2)O)(72)](42-), have been determined by single crystal X-ray diffraction. One compound exhibits a superposed kagome-lattice with huge channels whose diameters measure approximately 3.0 nm, while the arrangement of the Keplerate anions in the other compound approximates to a distorted cubic close packing.