Synthesis and studies of CuHg(NCX)4 (X = S,Se) and their complexes and application of the softness parameter in the elucidation of their structure

Complexes of CuHg(NCS)₄, CuHg(NCS)₂ (NCSe)₂ and CuHg(NCSe)₄ with tetrahydrofuran, dioxane, pyridine, 2-aminopyridine, nicotinamide, bipyridine and phenanthroline have been prepared and comparative studies made. Bipyridine and phenanthroline form cationic—anionic [CuL₃]²⁺ [Hg(SCN)₄]^2? (L = bipy, phen) complexes with CuHg(NCS)₄ and dinuclear bridged complexes with CuHg(NCSe)₄ and CuHg(NCS)₂ (NCSe)₂. For other ligands the nature of the complexes is binuclear or polynuclear. The comparative stability of the -XCN- bridge (X = S, Se) is CuHg(NCSe)₄ > CuHg(NCS)₂ (NCSe)₂ > CuHg(NCS)₄.     

Paper chromatography in the separation of ions

Summary A study has been made of the separation of alkali and alkaline earth metals. With mixtures of solvents, such as ethyl cellosolve, water and hydrochloric acid and acetone, water and hydrochloric acid in the ratio of 702010 and at different temperatures, a complete separation of alkaline earth metals was effected. Of the alkali metals only lithium, sodium and potassium could be separated from each other but rubidium and caesium always accompanied potassium.     

Effect of cholesterol on the properties of phospholipid membranes. 4. Interatomic voids

The properties of the interatomic voids present in fully hydrated dimyristoylphosphatidylcholine (DMPC)-cholesterol mixed membranes of different compositions are analyzed in detail using a generalized variant of the Voronoi-Delaunay method on the basis of computer simulation results. The systems investigated are chosen from both sides of the DMPC-cholesterol miscibility gap; the pure DMPC bilayer has also been included in the analysis as a reference system. The results obtained show that the empty space is organized in a more compact way, forming larger voids in the presence than in the absence of cholesterol. The voids located in the region of the rigid cholesterol rings become, on average, less spherical, oriented more parallel with the membrane normal axis with increasing cholesterol concentration, whereas an opposite effect of cholesterol is observed in the middle of the membrane among the chain terminal methyl groups. In general, the preferential orientation of the voids is found to strongly correlate with that of the molecules in the hydrocarbon phase of the membranes. The membranes are found to contain rather large voids, the volume of which can be an order of magnitude larger than the largest spherical cavities present in the systems. These voids are elongated or branching channels rather than big empty holes. The voids located among the DMPC and cholesterol molecules are lying preferably parallel with the membrane normal axis. The existence of such empty channels can be of great importance in the cross-membrane permeation of small, uncharged penetrants, in particular, of polar molecules.     

Reactions of unsaturated aldehydes with cyclopentadiene in solvents of various polarities

The rate constants of cycloaddition of cyclopentadiene to unsaturated aldehydes in different solvents cannot be correlated with a single parameter, in particular, the Brownstein parameter. The data set can be fitted only by multiparameter equations in which the decisive factor increasing the reaction rate is the capability of a solvent for electrophilic solvation. The same parameter also governs the ratio of the endo and exo isomers of the addition product.     

Synthesis,crystal structure,and magnetic properties of an alkoxo-hydroxo-bridged octanuclear copper(II) complex showing chemically significant hydrogen-bonding interactions involving a metallamacrocyclic core

A novel 16-member metallamacrocyclic octanuclear copper(II) complex of formulation [Cu8L4(OH)4] (1) has been prepared from a reaction of [Cu2L(O2CMe)] and NaOH in methanol, where L is a pentadentate trianionic Schiff base ligand N,N'-(2-hydroxypropane-1,3-diyl)bis(salicylaldimine). The complex has been characterized by analytical, structural, and spectral methods. It crystallizes in the monoclinic space group C2/c with the following unit cell dimensions: a = 30.365(3) A; b = 14.320(2) A; c = 19.019(2) A; beta = 125.33(2) degrees; V = 6746.7(13) A3; Z = 4. A total of 4589 unique data with l > 2 sigma (l) were used to refine the structure to R1(F0) = 0.0525 and wR2 = 0.1156. The structure consists of four binuclear [Cu2L]+ units linked covalently by four hydroxide ligands to form an octanuclear core which is stabilized by strong hydrogen-bonding interactions involving the hydroxide ligands. Each binuclear unit has a pentadentate ligand L showing N2O3 coordination with an endogenous alkoxide bridging atom. The magnetic susceptibility data of 1, obtained in the temperature range 14-306 K, show the presence of antiferromagnetic exchange interactions between adjacent spin-1/2 Cu(II) ions. The mu eff values are 1.54 and 0.26 microB (per copper) at 295 and 15 K, respectively. The magnetic data have been theoretically fitted using a Heisenberg spin-1/2 Hamiltonian with nearest-neighbor antiferromagnetic interactions. The spin coupling in the metallamacrocyclic ring has been modeled using four different coupling constants (J) on the basis of the structural parameters of the octanuclear core. The coupling constants obtained are J1 = -318.8, J2 = -293.3, J3 = -111.6, and J4 = -63.8 cm-1. The theoretical modeling of the susceptibility data gives a higher magnitude of the antiferromagnetic interaction within the binuclear [Cu2L]+ unit compared to those involving adjacent dimeric units.     

Use of Uracil Thin Layer for Measuring Biologically Effective UV Dose

Abstract— Dimerization of uracil monomers in a polycrystalline state by UV radiation changes the absorption characteristics of a thin layer of the material. The change in optical density, measured by spectrophotometry in the250–400 nm range, as a function of the exposure time is evaluated in terms of the biologically effective UV dose. A statistical evaluation of a great number of uracil dosimeters irradiated with a TL01 lamp from Philips establishes the possibility of evaluating the biologically effective UV dose using a uracil dosimeter. Nonlinear regression procedures were introduced to correct the absorption spectra for contributions due to light scattering and to determine the optical density values required to calculate the UV dose expressed in H^Uunits. Comparison of cumulative daily doses and long-term monitoring measured by the uracil thin-layer dosimeter and a phage T7 dosimeter are given, which allow the determination of conversion factors between various biological dosimeters under different irradiation conditions.     

Determination of thiocarbamyl sulphenamides, thiuram disulphides and dibenzothiazyl disulphide by amperometric titration

An amperometric method for the determination of thiocarbamyl sulphonamides has been developed, based on the cleavage of the S-N bond by hydriodic acid. The method can also be applied for the cleavage of the S-S bond in thiuram disulphides and dibenzothiazyl disulphide, and thus provides a useful means for the estimation of these compounds as well.     

Synthesis of some new fluorine containing 3-dialkylaminomethyl indoles, 3-indolylglyoxamides and tryptamines

Several new 2-(fluoroaryl)-3-dialkylaminomethylindoles, 3-acetyl-2-(fluoroaryl)-indoles, 2-(fluoroaryl)-3-indolylglyoxamides and corresponding tryptamines have been prepared as possible psychopharmacological agents. 2-(Fluoroaryl)-indoles have been synthesized by theFischer indole synthesis. 2-(Fluoroaryl)-indoles on treatment with oxalyl chloride and subsequent reaction with amines, gave 2-(fluoroaryl)-3-indolylglyoxamides. Some of these indolylglyoxamides were reducted with lithium aluminium hydride, to the corresponding tryptamines. 2-(Fluoroaryl)-indoles when subjected toMannich reaction afforded 3-dialkylaminomethyl-2-(fluoroaryl)-indoles. All these new compounds have been characterized by IR spectral studies.Possible Psychopharmacological Agents, Part XII, Part XI, J. Indian. Chem. Soc.57, 423 (1980).     

Molecular mechanism of physical gelation of hydrocarbons by fatty acid amides of natural amino acids

A variety of fatty acid amides of different naturally occurring l-amino acids have been synthesized and they are found to form gels with various hydrocarbons. The gelation properties of these compounds were studied by a number of physical methods including FTIR spectroscopy, X-ray diffraction, scanning electron microscopy, differential scanning calorimetry, rheology, and it was found that gelation depended critically on the fatty acid chain length and the nature of the amino acid. Among them l-alanine based gelators were found to be the most efficient and versatile gelators as they self-assemble into a layered structure to form the gel network. Mechanisms for the assembly and formation of gels from these molecules are discussed.