Wetting phenomena in the (3 × 1) phase of a model for H on Fe(110)

Interfaces between the three physically distinct, but equivalent domains in the (3 × 1) phase of a lattice gas model for the adsorbate system H/Fe(110) and its Ising analog are studied. In the ground state two types of wetting transitions are found where a light or a heavy domain wall decomposes into two heavy or two light walls separated by the third domain. These transitions give rise to wetting lines in the phase diagram which are located using Monte Carlo techniques.     

Bis-cyclometalated Ir(III) complexes as efficient singlet oxygen sensitizers

We report the singlet oxygen sensitization properties of a series of bis-cyclometalated Ir(III) complexes (i.e., (bt)2Ir(acac), (bsn)2Ir(acac), and (pq)2Ir(acac); bt = 2-phenylbenzothiazole, bsn = 2-(1-naphthyl)benzothiazole, pq = 2-phenylquinoline, and acac = acetylacetonate). Complexes with acetylacetonate ancillary ligands give singlet oxygen quantum yields near unity (PhiDelta = (0.7-1.0) +/- 0.1), whether exciting the ligand-based state or the lowest energy excited state (MLCT + 3LC). The singlet oxygen quenching rates for these beta-diketonate complexes were found to be small [(5 +/- 2) x 105 to (6 +/- 0.2) x 106 M-1 s-1], roughly 3 orders of magnitude slower than the corresponding phosphorescence quenching rate. Similar complexes were prepared with glycine or pyridine tethered to the Ir(III) center (i.e., (bsn)2Ir(gly) and (bt)2Ir(py)Cl; gly = glycine and py = pyridine). The glycine and pyridine derivatives give high singlet oxygen yields (PhiDelta = (0.7-1.0) +/- 0.1).     

Reaction of singlet oxygen with Ir(I) and Rh(I) thiolato complexes: oxidative addition vs. S-oxidation

Singlet oxygen reacts with Ir(I) and Rh(I) thiolato complexes to form the corresponding Ir(III) and Rh(III) peroxo thiolato complexes which do not undergo intramolecular oxidation of the thiolate moiety.     

2-Hydroxy-1, 1-Biphenyl- and -Binaphthyl-2′-Phosphines - Synthesis,Structure and Use in Rh-Catalyzed Carbonylation

Abstract

Dibenzofuran and dinaphthofuran are cleaved by lithium in presence of electron transfer catalysts to yield C,O-dilithium reagents. These are reacted with chloro- or alkoxyphosphines providing 2-hydroxy-1,l ‘-biphenyl-2’-phosphines and 2-hydroxy-1,‘-binaphthyl-2’-phosphines which form solvent complexes with O…H?O or P…H?O bridging bonds. The planes of the benzene rings of the biphenyl units are nearly perpen-dicular in the unit cell. Line form analysis of the temperature dependent solution NMR spectra of diastereoisomeric 2-HO-C₆H₄-C₆H₄-P (tBu)Ph revealed a barriere of rotation of Δ H= 12.87 kcal/mol. The respective 0-trimethylsilyl ethers have a higher barrier, and 2-hydroxybinaphthyl-2-phosphines dont racemize after separation by HPLC.     

Reactive functionalization of poly(lactic acid), PLA: Effects of the reactive modifier,initiator and processing conditions on the final grafted maleic anhydride content and molecular weight of PLA

A response surface methodology (RSM) design was used to analyze the effects of maleic anhydride (MA) and 2,5-bis(tert-butylperoxy)-2,5-dimethyl hexane (Luperox or L101) content, and TSE screw speed on the degree of grafted MA (MA_g) and number average molecular weight (M_n) of maleated PLA (PLA-g-MA), which can be used as a reactive compatibilizer in production of PLA blends with various components. PLA-g-MA's FTIR peaks indicated that MA was grafted onto the PLA backbone and oligomeric MA was also present. A maximum of 0.52 wt% MA_g determined by titration was achieved at the expense of a 50% reduction of M_n and an increase in the polydispersity index to around 2.0. Generally, increasing L101 increased the degree of grafting and decreased M_n. L101 and MA_g had a large effect on the stability of PLA-g-MA's M_n during storage. Nominally, amounts of MA equal to 4.5 wt%, L101 between 0.45 and 0.65 wt%, and screw speed of 20 rpm provided the optimal conditions for grafting MA onto PLA.     

Singlet oxygen generation from water-soluble quantum dot-organic dye nanocomposites

Water-soluble quantum dot-organic dye nanocomposites have been prepared via electrostatic interaction. We used CdTe quantum dots with diameters up to 3.4 nm, 2-aminoethanethiol as a stabilizer, and meso-tetra(4-sulfonatophenyl)porphine dihydrochloride (TSPP) as an organic dye. The photophysical properties of the nanocomposite have been investigated. The fluorescence of the parent CdTe quantum dot is largely suppressed. Instead, indirect excitation of the TSPP moiety leads to production of singlet oxygen with a quantum yield of 0.43. The nanocomposite is sufficiently photostable for biological applications.     

Interfacial Adsorption in Two-Dimensional Potts Models

The interfacial adsorption W at the first-order transition in two-dimensional q-state Potts models is studied. In particular, findings of Monte Carlo simulations and of density-matrix renormalization group calculations at q=16 are consistent with the analytic result, obtained in the Hamiltonian limit at large values of q, that Wt ^–1/3 on approach to the bulk critical temperature T _c, t=|T _c–T|/T _c. In addition, the numerical findings allow to estimate corrections to scaling. Our study supports and quantifies a previous conclusion by Bricmont and Lebowitz based on low temperature expansions.