Stabilisation of copper(II) tertiary-phosphine or -arsine complexes—II. Role of inductive effect and reaction conditions in stabilising copper(II)-arsine complexes of hybrid oxygen-arsenic ligands from o-R2AsC6H4CO2H

The characterization of the products of reactions between anhydrous/hydrated copper(II) acetate and the title acids having R = Me, C₆H₁₁, Ph and p-tolyl in different solvents and at different temperatures with the help of elemental analysis, TGA, DTA, room temperature magnetic susceptibility, IR, and UV-VIS and EPR spectral data reveal that a competition exists between the chelation of arsine to copper(II) on one side and the reduction of copper(II) to copper(I) and the subsequent chelation of the arsine to copper(I) and/or that of the arsine oxide to copper(II) on the other. This competition which is expected to be normally governed by the inductive effect of group R is disturbed by the change in reaction conditions leading to the conclusion that the reaction conditions rather than the inductive effect of the group R control the mode of reaction.     

Metal complexes of hybrid oxygen-arsenic ligands. Part V. A study of the products fromo-R2AsC6H4CO2M and CrO3 (M = H)/trans-[CrCl2(OH2)4]Cl · 2H2O (M = Na) in acetone

Summary A change of the reported medium of reaction oftrans- [CrCl₂(OH₂)₄]Cl · 2H₂O witho-R₂AsC₆H₄CO₂M (M = Na), from 95% ethanol to acetone, results in the change of an hydroxo — to an oxo — group (R = Ph), in the number of water molecules (R = Et or C₆H₁₁) and/or of ligand molecules (R =p-tolyl) in chromium(III)-arsine complexes. However, for R = Me, the same complex is obtained in each case. I.r. spectral data of these complexes favour the chelation of the carboxylate ion and non-coordination of arsenic(III) except for CrO(o-Ph₂AsC₆H₄CO₂) · 2.5 H₂O in which arsenic(III) of the monotertiary arsine group appears to coordinate to chromium(III). This would seem to be the first example of this type. On the other hand, the reaction of CrO₃ witho-R₂As- C₆H₄CO₂M (M = H) in 14.5 molar ratio in acetone yields only one type of complex,viz., [Cr₃O₃(o-R₂As(O)C₆H₄-CO₂)₂(o-R₂AsC₆H₄CO₂)(H₂O)₆] · n H₂O (n = 2, R = Me, C₆H₁₁ or Ph; n = O, R = Et). The arsine oxide molecules appear to chelate through As = 0 and the carboxylate oxygens while the arsine ligand binds only through the carboxylate oxygens leaving arsenic(III) uncoordinated as reported for the complexes obtained from the same reactants in 95% ethanol.     

The role of sequestering agents in the formation and structure of germanium anion cluster polymers

Large blue-green, transparent crystalline needles of [K-(2,2)diaza-[18]-crown-6]KGe(9).3en are prepared, in high yield, from the reaction of (2,2)diaza[18]-crown-6 in toluene with a solution of "KGe(4)" in ethylenediamine (en). The compound crystallizes in the orthorhombic space group Pnma (a = 10.9763(12) A, b = 27.265(3) A, c = 13.880(1) A; Z = 4). The crystal structure of [K-(2,2)diaza-[18]-crown-6]KGe(9).2en features one-dimensional [KGe(9)](-) bare intermetallic chains formed from the linking, via exo-bonds, of nido-Ge(9)(2-) clusters. Uncomplexed K atoms effectively cap the square bases of the monocapped square antiprismatic [Ge(9)](2-) clusters. The optical band gap of the title compound is 1.25 eV. The use of weaker sequestering agents in the isolation of Ge cluster anions from en solutions provides an additional handle in a controlled molecular route to preparing new low-dimensional Zintl phases.     

Synthesis of some 3-aryl-4-oxothiazolin-2-yl-[3-(2-aryl)indolyl]hydrazories

Several 4-aryl-l-[3-(2-aryl)indolyl]-3-thiosemiearbazones and 3-aryl-4-oxothiazolin-2-yl-[3-(2-aryl)indolyl] hydrazones were synthesized as possible antilertility agents. J. Heterocyclic Chem., 15 , 677 (1978)     

Electrorheological suspensions of laponite in oil: rheometry studies

We have studied the effect of an external direct current (DC) electric field ( approximately 1 kV/mm) on the rheological properties of colloidal suspensions consisting of aggregates of laponite particles in a silicone oil. Microscopy observations show that, under application of an electric field greater than a triggering electric field Ec approximately 0.6 kV/mm, laponite aggregates assemble into chain- and/or columnlike structures in the oil. Without an applied electric field, the steady-state shear behavior of such suspensions is Newtonian-like. Under application of an electric field larger than Ec, it changes dramatically as a result of the changes in the microstructure: a significant yield stress is measured, and under continuous shear the fluid is shear-thinning. The rheological properties, in particular the dynamic and static shear stress, were studied as a function of particle volume fraction for various strengths (including null) of the applied electric field. The flow curves at constant shear rate can be scaled with respect to both the particle fraction and electric field strength onto a master curve. This scaling is consistent with simple scaling arguments. The shape of the master curve accounts for the system's complexity; it approaches a standard power-law model at high Mason numbers. Both dynamic and static yield stresses are observed to depend on the particle fraction Phi and electric field E as PhibetaEalpha, with alpha approximately 1.85 and beta approximately 1 and 1.70 for the dynamic and static yield stresses, respectively. The yield stress was also determined as the critical stress at which there occurs a bifurcation in the rheological behavior of suspensions that are submitted to a constant shear stress; a scaling law with alpha approximately 1.84 and beta approximately 1.70 was obtained. The effectiveness of the latter technique confirms that such electrorheological (ER) fluids can be studied in the framework of thixotropic fluids. The method is very reproducible; we suggest that it could be used routinely for studying ER fluids. The measured overall yield stress behavior of the suspensions may be explained in terms of standard conduction models for electrorheological systems. Interesting prospects include using such systems for guided self-assembly of clay nanoparticles.     

Calreticulin Transacetylase Mediates the Acetylation of Nitric Oxide Synthase by Polyphenolic Acetate

Our earlier investigations identified acetoxy drug: protein transacetylase (TAase), a unique enzyme in the endoplasmic reticulum (ER) catalyzing the transfer of acetyl groups from polyphenolic acetates (PA) to certain functional proteins. Recently we have established the identity of TAase with ER protein calreticulin (CR) and subsequently transacetylase function of CR was termed calreticulin transacetylase (CRTAase). CRTAase was purified and characterized from human placenta. CRTAase catalyzed the acetylation of a receptor protein nNOS, by a model PA 7, 8-diacetoxy-4-methylcoumarin (DAMC), which was visually confirmed by using antiacetyl lysine. The aim of this report was to provide tacit proof by providing mass spectrometry evidence for CRTAase catalyzed acetylation of purified nNOS by DAMC. For this purpose, purified nNOS was incubated with DAMC and CRTAase, the modified nNOS was analyzed by nanoscale LC-MS/MS, which recorded 11 distinct peptides with a significant score as acetylated on lysine residues. The distribution was in order: lysines-24, -33, -38, -131, and -229 of the PDZ domain, Lys-245 of the oxygenase domain, Lys-754 and -856 of FMN binding domain, Lys-989 of connecting domain and Lys-1300, -1321, and -1371 of the NADPH-binding domain were acetylated. The results documented in this paper highlighted for the first time modification of nNOS by way of acetylation. Our earlier work recorded the profound activation of platelet NADPH cytochrome P-450 reductase and the acetylation of the reductase protein by DAMC, which also remarkably enhanced intracellular levels of nitric oxide. The results reported here coupled with the aforementioned previous observations strongly implicate the possible role of the acetylation of the reductase domain of nitric oxide synthase (NOS) in the NOS activation. In addition, the acetylation of nNOS can be expected to potentiate the interaction with CR, eventually leading to the augmented catalytic activity of NOS and expression of the related biological effects.     

Determination of the limit of absolute thermodynamic stability of liquid using external electric fields as perturbation

A relationship between the pressure and temperature of superheated liquid n-hexane and the critical electrostatic field required for inducing nucleation in it is obtained experimentally. This relation is used for the determination of the limit of stability of the liquid.     

Facile one pot multicomponent synthesis of novel 4-(benzofuran-2-yl)-2-(3-(aryl/heteryl)-5-(aryl/heteryl)-4,5-dihydro-1H-pyrazol-1yl)thiazole derivatives

An efficient base catalyzed one pot multicomponent reaction of aryl/hetryl chalcones, thiosemicarbazide and 1-(benzofuran-2-yl)-2-bromoethan-1-one was developed to synthesize the novel 4-(benzofuran-2-yl)-2-(3-(aryl/heteryl)-5-(aryl/heteryl)-4,5-dihydro-1H-pyrazol-1yl)thiazole derivatives.