Mononuclear complexes of manganese(II), iron(II), cobalt(II), nickel(II), copper(II), and zinc(II), with 4-amino-3,5-bis(pyridin-2-yl)-1,2,4 triazole and tris(2-aminoethyl) amine: crystal structure of [Ni(tren)(abpt)](NO3)2(H2O)2.25

Complexes of the type [M(tren)(abpt)](NO₃)₂(H₂O)_n (1–6) [M = Mn^II, Fe^II, Co^II, Cu^II, Zn^II (n = 2), Ni^II (n = 2.25), tren = tris(2-aminoethyl)amine, and abpt = 4-amino-3,5-bis(pyridin-2yl)-1,2,4 triazole] have been prepared. The bonding mode and overall geometry of the complexes have been deduced by elemental analyses, molar conductance values, spectral studies (obtained from FT-IR), ¹H-n.m.r., electronic spectral analyses and magnetic susceptibility measurements. A detailed molecular structure of complex (4) has been determined by single X-ray crystallography.     

Synthesis of new dinuclear dicopper(II) and dinickel(II) complexes. The kinetics of catechol oxidase and electrochemistry of a dicopper(II) complex

A new dinuclear ligand L, ethylene[OO-bis-salicylidene--diketone] bearing two symmetrical coordination sites was synthesized by the condensation of salicylaldehyde and acetylacetone, L, with 1,2-dibromoethane under reflux. The ligand L in a 1:1 ratio was treated with CuCl₂ and NiCl₂ to yield the complexes, tetrachloro bis[OO-bis- salicylidene--diketone copper(II)] and bis[OO-bis-salicylidene--diketone nickel(II)] chloride. The complexes were subsequently characterized by spectroscopic techniques, elemental analysis, i.r., ¹H-n.m.r., ¹³C-n.m.r., u.v.–vis., e.p.r. spectroscopy, and conductance measurements. The conductance measurements in DMF reveal that the Cu^II complex is covalent while the Ni^II complex is ionic and the spectral data support the Cu^II complex to be distorted octahedral whereas the Ni^II complex has square-planar geometry. The dioxygen binding was studied spectrophotometrically by the oxidation of tetrachloro bis[OO-bis-salicylidene--diketone copper(II)] with pyrocatechol in the presence of oxygen. The kinetic experiments were performed with the copper complex in DMF by monitoring the increase in absorbance over time at pH 8.0 in the presence of pyrocatechol at 25 °C. The kinetic parameters V_max and K_M were determined on the Michaelis–Menten Approach. Redox behavior of the dinuclear copper(II) complex was investigated by cyclic voltammetry in the presence of O₂ with the pyrocatechol (substrate) and also without the substrate. The large difference in potentials E⁰ is indicative of reversible oxygen binding of the complex and distinct catalytic activity.     

Interaction of manganese(II), iron(II), cobalt(II), nickel(II), copper(II) and zinc(II) with acetylhydrazine, formed in situ; first crystal structure of tris(acetylhydrazine) nickel(II) perchlorate

A series of transition metal complexes of the type [M(ah)₃](ClO₄)₂ (1–6) [M = Mn^II, Fe^II, Co^II, Ni^II, Cu^II and Zn^II, ah = acetylhydrazine] have been prepared by the reaction of M(ClO₄)₂ · 6H₂O with acetylhydrazine formed in situ by the reaction of hydrazine hydrate and acetylsalicylic acid methyl ester. The chelating behaviour of acetylhydrazine and overall geometry of these complexes have been spectroscopically investigated by means of FT-IR, ¹H-n.m.r. and electronic spectral techniques, as well as by elemental analysis data, molar conductance values and magnetic susceptibility measurements. Single X-ray structure determination of complex (4) revealed three acetylhydrazine ligands coordinated to nickel ion in a bidentate manner maintaining an octahedral environment. In all other complexes too, an octahedral geometry has been proposed on the basis of results obtained by various physico-chemical studies.     

On the geometry of null congruences in general relativity

Some theorems for the null conguences within the framework of general theory of relativity are given. These theorems are important in themselves as they illustrate the geometric meaning of the spin coefficients. The newly developed Geroch-Held-Penrose (GHP) formalism has been used throughout the investigations. The salient features of GHP formalism that are necessary for the present work are given, and these techniques are applied to a pair of null congruences C (l) and C(n).     

Synthesis,characterization, AC conductivity,and diode properties of polyaniline–CaTiO3 composites

Polyaniline–CaTiO₃ composites of different weight percentages were prepared by in situ polymerization. The prepared composites were characterized by Fourier transform infrared spectroscopy for structural studies, and a morphology analysis was carried out by scanning electron microscopy studies. Real and imaginary parts of the complex impedance were determined for given samples as a function of frequency. Current–voltage and capacitance–voltage measurements were also carried out. The carrier mobility μ values of neat polyaniline and polyaniline–CaTiO₃ composites were found to be 5.37 × 10^?3 and 2.73 × 10^?2, respectively, and a significant enhancement, as compared with the reported data, was observed. Therefore, this study may provide a better route for technological applications in all fields in the near future and can also be represented by a pure electronic model. Copyright © 2013 John Wiley & Sons, Ltd.     

An Efficient and Convenient Synthesis of Imidazolines and Benzimidazoles via Oxidation of Carbon‐Nitrogen Bond in Water Media

The metal coordination complex K₄[Fe(CN)₆] is an efficient and environmentally benign catalyst for the synthesis of imidazolines and benzimidazoles from various aldehydes and 1,2‐diamines in aqueous medium at room temperature. This protocol gives excellent yield of product with desired purity.     

Novel Pyrimidine‐based Ferrocenyl substituted Organometallic Compounds: Synthesis,Characterization and Biological Evaluation

Some novel pyrimidine‐based ferrocenyl substituted organometallic compounds were synthesized via multistep reactions, well characterized by different spectroscopic techniques and elemental analyses and evaluated for in vitro antiprotozoal susceptibility against HM1: IMSS strain of Entamoeba histolytica. The results of antiprotozoal susceptibility unveiled these compounds, as new leads in protozoal chemotherapy as most of the organometallics displayed an exceptionally higher antiamoebic activity (IC₅₀ = 0.055 μM ‐ 0.815 μM) than the reference drug metronidazole which gave IC₅₀ (50% inhibitory concentration) value 1.781 μM in our experiments, concluding that newly synthesized organometallic compounds have potential to be employed as effective antiamoebic agents and these organometallics can be very useful for further optimization work on amoebic chemotherapy.     

Hydrotropic Behavior of Sodium Salicylate in Presence of Additives

It is well known that, like surfactants aggregating at a certain concentration (called critical micelle concentration, CMC), hydrotropes also have minimum hydrotrope concentration (MHC). However, unlike surfactant CMC, this MHC value is usually very high, thereby reducing their application. In this paper we report the results of conductivity and viscosity measurements with a well known hydrotrope sodium salicylate (NaSal) solutions in presence and absence of additives (propanol, PrOH; butanol, BuOH; pentanol, PeOH and tetrabutylammonium bromide, Bu₄NBr). We have found that MHC value of NaSal decreases in presence of additives. Alcohols increase the hydrophobic interactions and decrease the MHC while Bu₄NBr, in addition to ameliorating the hydrophobic interactions, reduces the charge on head groups and MHC decreases more steeply in its presence. Increased solubility of riboflavin in NaSal containing the above additives corroborates the results.     

Blue shifts of the C-H stretching vibrations in hydrogen-bonded and protonated trimethylamine. Effect of hyperconjugation on bond properties

The optimized geometry of isolated trimethylamine (TMA), its hydrogen bond complexes with phenol derivatives and protonated TMA is calculated at the B3LYP/6-31++G(d,p) level. A natural bond orbital (NBO) analysis on these systems is carried out at the same level of theory. In isolated TMA, one of the C-H bond in each of the three CH(3) groups is more elongated than the two other ones. As revealed by the NBO data, this results from a hyperconjugative interaction from the N lone pair to the sigma*(C-H) orbitals of the C-H bonds being in a transoid position with respect to the N lone pair. The formation of an intermolecular OH...N hydrogen bond with phenols results in a decrease of the lone pair effect. A linear correlation is found between the decrease in occupation of the sigma*(C-H) orbitals and the decrease in the hyperconjugative interaction energy in the complexes and isolated TMA. Complex formation with phenols results in a blue shift of 55-74 cm(-1) of the C-H stretching vibrations involved in the lone pair effect. Smaller blue shifts between 14 and 23 cm(-1) are predicted for the other C-H bonds. In these complexes, a linear correlation is found between the frequency shifts and the elongation of the C-H bonds. Protonation of TMA results in a nearly equalization of all the C-H distances and a blue shift of 180 cm(-1) of the C-H bonds involved in hyperconjugation with the N lone pair.