Cis di-oxomolybdenum(VI) complexes with a tridentate ONO donor ligand; synthesis,X-ray crystal structure,spectroscopic properties and oxotransfer chemistry

The molybdenum complexes of Schiff base ligands viz. [MoO₂LH₂O] where L¹ = tris(hydroxymethyl)(salicylide-neamino)methane, L² = tris(hydroxymethyl)(2,3-dihydroxybenzylideneamino)methane and L³ = tris(hydroxymethyl)(2,3,4-trihydroxybenzylideneamino)methane have been synthesized and characterized by spectroscopic and electrochemical techniques. The X-ray crystal structure of the complex [MoO₂L¹H₂O] reveals a distorted octahedral geometry with one ligand and a water molecule coordinated to the MoO₂ center. No previous complex of this type contains a coordinated water molecule. The complex undergoes an oxotransfer in the presence of Bu₃P to form a -oxobridged molybdenum(V,V) dimer. This rules out Mo—S coordination as a prerequisite for oxotransfer in such molybdenum(VI) complexes.     

Time-resolved spectroscopy of long-path fluorescence and scattering for measuring total absorption of fluids

Optical methods are appropriate tools to detect organic micro-pollutants in fluids. A new technique is introduced which uses the decay of interaction processes like fluorescence and elastically scattered radiation by a fluid. Principally two different parameters are determined:

1. (i) the decay-time of the conventional interaction τ_C, which occurs at relatively short path-lengths of the incidence beam in the fluid, and

2. (ii) the decay-time τ_MP of the multi-path-saturation interaction originating at long path-lengths, e.g. in multi-path-reflection cuvettes, where the incidence beam is fully absorbed by the fluid.

A relation between the decay-time and the absorption coefficient of a fluid is theoretically derived. A simple preliminary experiment is performed considering distilled water polluted with non-fluorescent azobenzene and fluorescent quinine-sulphate. A nitrogen laser has been used to generate the fluorescence and scattering signals. The reciprocal value of the difference between the decay-time of the multi-path and conventional signals, 1/(τ_MP − τ_C), yields the total absorption coefficient directly. In comparison to the conventional absorption technique the decay-time method is characterized by a higher sensitivity.     

SYNTHESIS OF POSITIVELY CHARGED PHTHALOCYANINES and THEIR ACTIVITY IN THE PHOTODYNAMIC THERAPY OF CANCER CELLS

Positively charged zinc containing or metal free phthalocyanines 6a-c and 7a-c were prepared via a three step procedure starting from 4-nitrophthalonitrile. The phthalocyanines contain alkyl chains of different length in order to influence the hydrophilic vs lipophilic character of the compounds. The partition between a hydrophilic (water) and lipophilic (octanol-1) phase was determined, and the photoredox activities were investigated. Initial results on the photodynamic activity of these compounds were compared with those of Dougherty's Photofrin II on different malignant and non-malignant cell lines (XP 29MAmal, CX1, HeLa, S180 and NO17). Positively charged phthalocyanines in vitro showed a higher photodynamic activity than Photofrin II.     

Metal-based anticancer agents: targeting androgen-dependent and androgen-independent prostate and COX-positive pancreatic cancer cells by phenanthrenequinone semicarbazone and its metal complexes

A planar, polycyclic and aromatic hydrocarbon ligand, namely 9,10-phenanthrenequinone semicarbazone, and its transition metal complexes have been synthesized and structurally characterized. The in vitro antiproliferative activity of these compounds against five human cancer cell lines revealed that they were effective against androgen receptor-positive/negative prostate cancer cells as well as COX-positive pancreatic BxPC-3 cancer cell line. The driving force behind such antiproliferative activity seems to be the up-regulated COX expression in these cells, which was amenable for targeting through metal complexation. These structural motifs can, therefore, serve as a starting point for developing novel cytotoxic agents against the growing number of prostate and pancreatic cancers.     

On the Preparation of ZnO Single Crystals

ZnO single crystals were prepared by means of two methods:i slow cooling of ZnO/PbF₂ (PbO) high temperature solution, (ii) flux reaction technique, hydrolysis of ZnF₂ in PbF₂ as a solvent. At cooling rate ≥ 0.9 K/h the known plates, hexagonal prisms, and hollow crystals were obtained. At the cooling rate 0.6 K/h compact crystals have grown. This habit was also formed with the flux reaction technique. An estimation of the deposition rates of both methods has shown approximative agreement between the cooling runs with 0.6 K/h and the flux reaction technique under the chosen conditions. The deposition rate appears to be a relevant parameter for forming compact ZnO crystals in these systems.     

FT-NIR Spectroscopy of some long-chain fatty acids and alcohols

Fourier-transform (FT) near-infrared (NIR) spectroscopy has proved to be a powerful technique in investigating structure and thermodynamic properties of long-chain fatty acids and alcohols. In order to extract useful information from the NIR spectra, bands due to the second as well as first overtones of OH-stretching modes of the monomeric forms were employed. It has been also found that two-dimensional (2D) NIR correlation spectroscopy can accentuate useful information often obscured in the complicated NIR spectral data set.     

Proposals for structure and effect of methylalumoxane based on mass balances and phase separation experiments

Methylaluminoxane prepared from trimethylaluminium on a surface of ice mainly can be described as [Al₄O₃(CH₃)₆]₄. This is shown through analysis, phase separation experiments with diethyl ether and molecular weight determinations in benzene, 1, 4-dioxane, tetrahydrofuran and trimethylaluminium. It is discussed that the reason for forming this ball-like structure is the saturation of four coordinated Al₄O₃(CH₃)₆. This molecule has a cavern which contains a solvent molecule or a molecule of trimethylaluminium. The consequences for the formation of the catalytically active structure together with metallocene are discussed.     

Transport Coefficients and Structural Principles of PbO?Ga2O3 Melt

More Precise knowledge of the growth mechanism of garnets in form of epitaxial layers or single crystals in high temperature solutions on the base of trivalent oxides Me₂O₃ in PbO B₂O₃ solvent is desirable. Data of physicochemical properties of the melts especially density, shear viscosity, and electrical conductivity and their dependence on the temperature are useful in endeavour to recognize the structural principles of oxidie melts. Therefore as a first step the binary system PbO Ga₂O₃ was investigated to understand the influence of the Ga component on a complete mixed garnet solution, for instance (Y, Sm)₃ (Fe, Ga)₅O₁₂ in PbO B₂O₃ solvent.