Intense fluorescence of metal-to-ligand charge transfer in [Pt(0)(binap)(2)] [binap = 2,2'-bis(diphenylphosphino)-1,1'-binaphthyl

[Pt(0)(binap)(2)] (binap = 2,2'-bis(diphenylphosphino)-1,1'-binaphthyl) is found to exhibit a luminescence from metal-to-ligand charge transfer state (MLCT) with a quantum yield of 0.12 and a lifetime of 1.2 micros in toluene at an ambient temperature. Prompt fluorescence with a quantum yield of 1.6 x 10(-)(4) is observed by means of a picosecond time-correlated single photon counting technique. The spectrum of the steady-state luminescence is almost identical to that of the prompt fluorescence, indicating that the intense luminescence is mainly delayed fluorescence from thermally activated (1)MLCT. The analysis of the temperature-dependent emission indicates that the energy difference between the (1)MLCT and (3)MLCT is 1.15 x 10(3) cm(-)(1). The lifetime of the prompt fluorescence is determined to be 3.2 ps from the decay of stimulated emission overlapped on subpicosecond transient absorption spectra. The lifetime of the (1)MLCT is much longer than expected from the large spin-orbit coupling constant of 5d (Pt) electrons (4000 cm(-)(1)). Theoretical analysis based on density functional theory reveals that structural distortion in the MLCT states causes large energy splitting between HOMO and HOMO - 1, which prevents a very fast ISC induced by strong spin-orbit interactions between these orbitals. The relatively slow ISC is therefore induced by weak spin-orbit interactions (ca. 50 cm(-)(1)) between ligand-centered molecular orbitals. Theoretical calculations indicate that the phosphorescence observed at lower temperatures is due to intensity borrowing from 4(1)B(2) --> GS transition. However, the large energy difference between HOMO and HOMO - 2 reduces the extent of mixing between the lowest (3)MLCT and 4(1)B(2) due to spin-orbit interaction, thereby decreasing the radiative rate of the phosphorescence.     

Synthesis and structure of a seven electron triangular cluster complex [Mo3S4Cl3(dppe)2(PEt3]

The triangular six-electron cluster complex [Mo₃S₄Cl₄(PEt₃) _x (thf)₅] produced by the excision reaction of Mo₃S₇Cl₄ with triethypholsphine is reduced by magnesium at – 20°C. Subsequent addition of dppe (=1,2-his(diphenylphosphino)ethane) to the reduced species affords a seven-electron triangular cluster complex [Mo₃S₄Cl₃(dppe)₂(PEt₃)]. The complex crystallizes in the space groupCm witha=17.170(6),b-19.878(6),c = 13.289(5) = 121.73(2)°,V = 3858(2) A³, andZ = 2. The structure shows an almost equilateral triangle of three molybdenum atoms capped by a Sulfur atom and bridged by three sulfur atoms. The Mo Mo distances, ranging from 2.804(1) to 2.809(1) A are elongated ca. 0.04 A as compared with lose of a six-electron cluster complex with drape ligands. Two molybdenum atoms have a chlorine and a dppe ligands, and the other molybdenum atom bas a chlorine and a triethylphosphine ligands. The UV-Vis spectrum has a characteristic broad hand centered at 1410 n m, which is not observed for six-electron clusters. The ESR spectrum indicates the presence of an unpaired electron consistent with the formulation of the compound as a seven-electron cluster.Dedicated to Professor fiaxi Lu on the occasion of his 80th birthday.     

Rainbow scattering of CO and N2 from LiF(001)

The angular intensity distributions of CO and N(2) molecules scattered from a LiF(001) surface have been measured as functions of surface temperature, incident translational energy, and incident azimuthal direction affecting surface corrugation at a high resolution. Although both molecules have the same molecular mass and linear structure, only the CO molecule shows a rainbow feature in its scattering pattern, while the N(2) molecule shows a single peak distribution. From the comparisons of the obtained results with the calculated predictions based on the newly developed classical theory of the ellipsoid-washboard model, the differences in scattering distribution are attributed to the effects of molecular anisotropy and center-of-mass position. With an increase in the extent of the molecular anisotropy such as that of N(2) and CO as compared with rare-gas atoms, the summation of several scattering distributions depending on molecular orientation results in smearing the rainbow scattering on the corrugated surface. This smearing effect, however, attenuates when center-of-mass position deviates from the molecular center, as that for CO.     

Oxygen atom transfer reactions from dioxygen to phosphines via a bridging sulfur dioxide in a trinuclear cluster complex of rhenium, [(Ph(3)P)(2)N][Re(3)(mu(3)-S)(mu-S)(2)(mu-SO(2))Cl(6)(PMe(2)Ph)(3)

A trinuclear rhenium sulfide cluster complex, [(Ph(3)P)(2)N][Re(3)(mu(3)-S)(mu-S)(3)Cl(6)(PMe(2)Ph)(3)], synthesized from Re(3)S(7)Cl(7), dimethylphenylphosphine, and [(Ph(3)P)(2)N]Cl is readily converted to a bridging SO(2) complex, [(Ph(3)P)(2)N][Re(3)(mu(3)-S)(mu-S)(2)(mu-SO(2))Cl(6)(PMe(2)Ph)(3)], by reaction with O(2). The oxygen atoms on the SO(2) ligand react with phosphines or phosphites to form phosphine oxides or phosphates, and the original cluster complex is recovered. The reaction course has been monitored by (31)P NMR as well as by UV-vis spectroscopy. The catalytic oxygenation of PMePh(2) in the presence of the SO(2) complex shows that turnovers are 8 per hour at 23 degrees C in CDCl(3). The X-ray structures of the cluster complexes are described.     

Spectroscopic Mimicry for the Protonated Retinal Schiff Base in vivo with Modified Amphiphilic Clay Interlayers as a Possible Model of Opsin Environment

Abstract— We have found that clay acts as a novel model matrix for the amphiphilic protein-opsin to mimic the visible absorption spectrum of a protonated retinal Schiff base (RSB) in vivo. Without strong acids at ambient temperature, a visible broad absorption spectrum with a LDmax at 530 nm covering the range from 400 to 680 nm was achieved for the protonated RSB with cationic surfactant-modified montmorillonite clay. The interlayers of the dimethyloctadecylamine (DOA) modified clay were found to provide amphiphilic space allowing the amphiphilic RSB to be intercalated easily and sequentially and protonated by the DOA. It is proposed that the visible absorption spectrum at LD, 530 nm was attributable to electrostatic effects, permitting the appropriate distance between the nitrogen of the protonated RSB and the negatively charged clay interlayers and also to the anisotropic orientation of the RSB molecules in the interlayers.     

A methode for preparing an aqueous colloidal dispersion of organic materials by using water-soluble polymers: Dispersion ofΒ-carotene by polyvinylpyrrolidone

Summary A new method was developed for preparing an aqueous colloidal dispersion ofΒ-carotene. This method consists of preparing a solid mixture ofΒ-carotene and polyvinylpyrrolidone (PVP) from their chloroform solution by evaporating the solvent and dissolving the mixture into water. From filtration experiment and electron microscopic observation it was found thatΒ-carotene in its aqueous dispersion exists as colloidal particles with a diameter of about 100 ?. Spectroscopic data evidenced thatΒ-carotene is molecularly dispersed in solid of PVP. It was considered that PVP acts as a solid solvent forΒ-carotene and, at the same time, a stabilizing agent for its aqueous dispersion. Instead of PVP, such a hydrophilic-oleophilic substance as methylcellulose, polyvinylmethylether or Aerosol OT could be also used as the dispersing agent. Other materials thanΒ-carotene could be dispersed by similar technique.

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Zusammenfassung Es wird eine neue Methode zur Pr?paration einer w?\rigen Kolloid-Dispersion vonΒ-Carotin beschrieben. Diese Methode besteht aus Herstellen einer festen Mischung ausΒ-Carotin und Polyvinylpyrrolidon (PVP) aus der Chloroforml?sung durch Verdampfen des L?sungsmittels und anschlie\ende L?sung der Mischung in Wasser. Aus Filtration und elektronenmikroskopischen Aufnahmen l?\t sich zeigen, da\ dasΒ-Carotin molekulardispers im festen PVP verteilt ist. Das PVP wirkt offensichtlich als festes L?sungsmittel fürΒ-Carotin und gleichzeitig als stabilisiertes Agens für die w?\rige Dispersion. Anstelle von PVP k?nnen auch derartige hydrophile-oleophile Substanzen wie Methylcellulose, Polyvinylmethyl?ther oder Aerosol OT verwendet werden. Es k?nnen auch andere Materialien alsΒ-Carotin auf gleiche Weise dispergiert werden.

     

Unusual C25 steroids produced by a sponge-derived Penicillium citrinum

[structure: see text] Structurally unique steroids, isocyclocitrinol A (1) and 22-acetylisocyclocitrinol A (2), were isolated from the extract of a saltwater culture of sponge-derived Penicilliun citrinum. The structures were established by analysis of 1D and 2D NMR data. The absolute structures were determined on the basis of X-ray structure analysis and application of modified Mosher's method. Furthermore, the structure of cyclocitrinol (3a) previously isolated from a terrestrial P. citrinum was revised as 3b. Compounds 1 and 2 showed weak antibacterial activity against Staphylococcus epidermidis and Enterococcus durans.     

Polyelectrolyte complex films derived from polyethyleneoxide-maleic acid copolymer and chitosan: preparation and characterization

Polyelectrolyte complex films were prepared with polyethyleneoxide-maleic acid copolymer and chitosan using a casting/solvent evaporation method. The films were examined in terms of their IR spectra, surface and cross-section morphologies, cytotoxicity, and swelling behavior at different pH levels. To assess the potential of these films as a biomedical device, the profiles of the release of model drug from the CS/PEOMA films were examined at pH 4.8. The surface morphology of the films was quite smooth and uniform, and the cross-sectional morphology was dense and homogeneous. The swelling behaviors of CS/PEOMA films were found to depend on the pH of the solution as well as on the CS/PEOMA composition. Drug release from different CS/PEOMA films at pH 4.8 was found to be dependent on film composition. The results showed the potential applicability of CS/PEOMA film as a drug delivery vehicle.     

Temperature control technology by heat capacity change upon lock and key binding

We propose an innovative temperature control technology wherein a heat capacity change upon lock and key binding is applied. A proof-of-principle calculation is performed using a three-dimensional integral equation theory of a statistical mechanics of fluid (Ornstein-Zernike theory coupled by HNC closure). Logical correctness of the temperature control technology is verified by this calculation. The performance of the heat pump is discussed. In addition, a more effective condition of the heat pump is also discussed to improve the performance.     

Interlayer Reaction of Polyamine/α-Zirconium Phosphate Intercalation Compounds with Some Aldehydes

Abstract

The intercalation compound between α-zirconium phosphate and N,N′-bis-(3-aminopropyl)-1, 3-propanediamine has two different modifications with respect to the conformation of the guest amine molecules: one is “bent form” and the other “straight form”. Reactivity of each phase with a series of aldehydes was examined. ¹³C CP/MAS NMR indicated that the tetraamine reacts stereoselectively with aldehydes to form cis-imine in the interlayer spacing. Depending on the molecular size of aldehyde, it is found that a significant difference can be recognized in the yields of the imine products for the two phases of intercalation compounds. It is also noted that residual water molecules in the interlayer spacing play an important role in the imine formation reaction.