Carbohydrate phosphinites as chiral ligands for asymmetric synthesis catalyzed by complexes : V. New rhodium(I)-chelates prepared by precipitation from the equilibrium between neutral and cationic complexes and hydrolysis of their bonded ligands

Some byproducts of the preparation of cationic rhodium(I)bis(phosphinite)-chelates 3 from rhodium(I)-[(Z,Z)-cycloocta-1,5-diene]-acetylacetonate, 4,6-O-alkylidene-glucopyranoside-2,3-O-bisphosphinite 1, such as ligand and acid HA can be isolated. Neutral bis(phosphinite)complexes 2 having acetylacetonate as chelating anion and being inactive to hydrogenation, are separated from the equilibrium with cationic complexes 3 by precipitation using polar solvents. The acids, HA, as catalysts for solvolysis give the new cationic chelates 4 in a prolonged reaction. The chelates 4 exhibit excellent catalytic properties in asymmetric hydrogenation and possess free hydroxy groups in the 4,6 positions of the carbohydrate ligand.     

Stability and diffusion of surface clusters

Using kinetic Monte Carlo simulations and a bond-counting ansatz, thermal stability and diffusion of an adatom island on a crystal surface are studied. At low temperatures, the diffusion constant D is found to decrease for a wide range of island sizes like , where is close to one, N being the number of adatoms in the cluster. By heating up the surface, the system undergoes a phase transition above which the island disappears. Characteristics of that transition are discussed. Received 20 January 1999     

Ising cubes with enhanced surface couplings

Using Monte Carlo techniques, Ising cubes with ferromagnetic nearest-neighbor interactions and enhanced couplings between surface spins are studied. In particular, at the surface transition, the corner magnetization shows nonuniversal, coupling-dependent critical behavior in the thermodynamic limit. Results on the critical exponent of the corner magnetization are compared to previous findings on two-dimensional Ising models with three intersecting defect lines.     

Lattice gas models with competing interactions

The phase diagrams of lattice gas models on square and centred rectangular lattices with short range competing pair interactions and three-body forces are studied using Monte Carlo techniques and the transfer matrix method. A variety of commensurate (C) phases can be described as observed experimentally for adsorbed monolayers like H on Pd(100), O on W (110) and especially H on Fe(110). In addition, due to the competition between different C phases incommensurate (IC) structures may occur. Their properties and related aspects (C-IC transitions, disorder lines) are discussed in connection with the widely studied ANNNI model, and general concepts on two-dimensional C and IC phases and experiments. Also dynamic properties — such as the self-diffusion of the adsorbate at the surface — are briefly mentioned.     

On the dynamics of Heisenberg magnets with lattice anisotropy near the phase transition

The kinetic theory (mode-mode coupling theory) is applied to lattice anisotropic Heisenberg ferromagnets and anti-ferromagnets in the paramagnetic region near the phase transition. The distinction of a hydrodynamic and a critical region is refined by introducing regimes of essentially lower-dimensional (1-d or 2-d) behavior and three-dimensional behavior of the magnet. In the regime of 3-d behavior the scaling function of the line-width of the dynamic spin correlation function is discussed extensively.     

Interfacial adsorption in planar potts models

Zeitschrift für Physik B Condensed Matter - The net adsorption,W, of non-boundary states at interfaces in two-dimensional Potts models is studied using Monte Carlo techniques. For the...     

Titanium dioxide-tetra sulphonatophenyl porphyrin nanocomposites for target cellular bio-imaging and treatment of rheumatoid arthritis

Photodynamic therapy (PDT) is one of the latest biomedical technologies used for treatment of various neoplastic and non-neoplastic diseases. However, there still exist some well-known problems regarding its efficacy, e.g. effective concentration of the drug at the desired sites, the irradiation light dosimetry and biocompatibility of the photosensitizer. The introduction of nanotechnology and nanomaterial like biocompatible nano-titania (i.e., nano-TiO₂) may facilitate to solve some of these problems. In this study we have explored the possibility of combining tetra sulphonatophenyl porphyrin (TSPP) with nano-titania (PT) for efficient PDT with least adverse effects. The spectroscopic properties of these nano-composites were characterized by using fluorescence and UV-Vis absorption spectroscopic study. The singlet oxygen quantum yield was determined by using 2,5-diphenyl-3,4-benzofuran (DPBF), while the effect of nano TiO₂ with TSPP on the synovial fibroblast cells from human (HSC) and rat models (RSC) were investigated by confocal laser microscopy and 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay. Our results suggest that nano TiO₂ with TSPP can be readily utilized for effective PDT treatment of Rheumatoid Arthritis (RA).