Versatility of 2,6-diacetylpyridine (dap) hydrazones in stabilizing uncommon coordination geometries of Mn(II): synthesis, spectroscopic, magnetic and structural characterization

Five seven- or eight-coordinate manganese complexes of hydrazone ligands have been prepared. Three seven-coordinate neutral Mn(II) complexes: [Mn(dapA2)]n (1), [Mn(dapB2)(H2O)2] (2), [Mn(dapS2)(H2O)2] (3) have been synthesized from the bis-Schiff bases of 2,6-diacetylpyridine: dap(AH)2, dap(BH)2 and dap(SH)2 (AH = anthraniloyl hydrazide, BH = benzoyl hydrazide, SH = salicyloyl hydrazide), respectively. Two eight-coordinate Mn(II) complexes: [Mn(dapS)2] (4) and [Mn(dapB)2].3H2O (5) have been synthesized from the mono-Schiff bases dapBH and dapSH, respectively. The complexes have been characterized by elemental analyses and by IR, UV-Vis., FAB mass, EI mass and EPR spectroscopy. The molecular structures of 1, 3.DMF and 4.DMF have been determined by single-crystal X-ray diffraction. The mono-Schiff bases are monoanionic and the bis-Schiff bases are dianionic. The octa-coordinated mono-Schiff base complex 4 adopts a dodecahedral geometry, while the hepta-coordinated bis-Schiff base complex 1 forms a one-dimensional linear polymeric chain. A weak antiferromagnetic exchange interaction (J=-0.15 cm(-1)) between the Mn(II) ions in is attributed to weak Mn...Mn interaction through the PhNH(2) moiety of the ligand, as indicated by extended-Hückel molecular orbital calculations. A good simulation of the EPR spectrum of a frozen solution (DMSO at 4 K) of compound 1 was obtained with g=2.0, D=0.1 cm(-1), E=0.01 cm(-1). The EPR spectrum of a powdered sample of compound 1 shows a large broadening of the signal, due in part, to the important zero-field splitting of the hepta-coordinated Mn(II) ion.     

Quantum Superarrivals: Bohr's Wave-Particle Duality Revisted

The phenomenon of quantum superarrivals is manifested in the probabilities for Schrödinger wave packets scattered from perturbed potential barriers. We argue that both classical wave-like and classical particle-like properties can be exhibited in the same gedanken experimental set-up for obtaining superarrivals through Schrödinger dynamics. An interesting question regarding the tenet of mutual exclusiveness, a la Bohr, of these two properties is raised in the context of this phenomenon.     

57Fe Mössbauer investigation of naturally oxidised chlorite

The green chlorite, occurring as monomineralic mass in the Sukinda (India) area has been investigated by⁵⁷Fe Mössbauer spectroscopy together with IR, XRD and XRF analyses. The Mössbauer spectra (at RT and 100 K), split into four symmetric doublets, show hyperfine parameters suggesting Fe²⁺ atcis and brucite sites and Fe³⁺ attrans andcis sites. The results show that susceptibility to oxidation (Fe²⁺→Fe³⁺) is highest in thetrans site, moderate in thecis site, and least in the brucite site.     

Analysis of conducting-system frequency response data for an interfacial amorphous phase of copper-core oxide-shell nanocomposites

Complex electrical-conductivity experimental data sets for the interfacial amorphous phase in copper-core-copper-oxide-shell nanostructured composites have been analyzed using two Kohlrausch-related frequency response models recently developed for analysis of the dispersive electrical response of conductive materials. Such analysis has been carried out for both the precursor (herein referred to as the reference) glass as well as the glass in which the core-shell nanostructure was developed after suitable heat treatment. Complex nonlinear-least-squares data fitting at each temperature employed composite Kohlrausch models that included electrode effects. Because of the lack of sufficient high-frequency data, it was necessary to use fixed, rather than free, values of the shape parameter beta1 of the model. On the basis of topological considerations, its values were set at 13 and 23 for the reference glass and the core-shell structured glass, respectively. The activation energies of resistivity for the reference and the treated glasses were found to have values of about 2 and 0.4 eV, respectively, indicating two different mechanisms of electrical conduction. A blocking-electrode measurement on the reference glass indicated the presence of an electronic as well as an ionic component of the electrical conductivity, with the ionic part dominating at the temperatures for which the present analyses were carried out.     

Search for DeltaS = 2 nonleptonic hyperon decays

A sensitive search for the rare decays Omega(-)--> Lambdapi(-) and Xi(0)--> ppi(-) has been performed using data from the 1997 run of the HyperCP (Fermilab E871) experiment. Limits on other such processes do not exclude the possibility of observable rates for |DeltaS| = 2 nonleptonic hyperon decays, provided the decays occur through parity-odd operators. We obtain the branching-fraction limits B(Omega(-)-->Lambdapi(-)) < 2.9 x 10(-6) and B(Xi(0)--> ppi(-)) < 8.2 x 10(-6), both at 90% confidence level.     

Direct measurement on transparent plates by using Fizeau interferometry

It is shown that Fizeau interferometry provides an accurate optical method to measure the refractive index and wedge angle of transparent plates used as optical components in different experiments. A near IR external cavity diode laser having spectral resolution up to 10⁻⁷ has been employed to measure the refractive index of the test plates by introducing amplitude modulation technique in the detection system of our phase shifting Fizeau interferometry. Detection of spatial fringes has been performed to find out the wedge angles of the plates by using a He–Ne laser along with the CCD-image sensor.     

Collapse-induced quantum nonlocal effect

In this article we attempt to bring out some significant general aspects of what we call collapse-induced quantum nonlocal effects resulting from the use of the hypothesis of wave function collapse.     

Occurrence of monoalkyllead species during the speciation of organolead

When tri-levels are determined in environmental samples by a method based on Grignard derivatization and subsequent gas chromatography/atomic absorption spectrometry, monoalkyllead species are sometimes detected. A rearrangement process during or following Grignard derivatization explains this occurrence at least partly. The accuracy of the determination does not suffer significantly from this limited-scale reaction but the detection of a monoalkyltributyllead species does not necessarily mean that the sample contains monoalkyllead compounds.     

Solid State Annular Tautomerism in a Molecule Containing Two Imidazole Moieties

Abstract  The X-ray crystal structure of the 1:2 condensate (1) of hydrazine hydrate and 4-methyl-imidazole-5-carboxaldehyde has been determined. The molecule is centrosymmetric crystallising in the space group Fddd with cell dimensions: a = 10.557(14), b = 17.062(22), c = 24.759(27) ?. Fourier map shows that the NH hydrogen atom of each imidazole moiety has equal possibility of occupying any of its two ring N atoms. This poses the possibility of finding three tautomers in 1 in the solid state. Consideration of the H-bonding pattern observed in 1 and related B3LYP/6-311+G(2d,p) calculations show that only two tautomers are present in the solid state. The situation is compared with that in the structure of 4(5)-nitro-5(4)-methoxy-imidazole reported previously by Kubicki. Graphical Abstract   The inherent disorder of the ring N–H hydrogen atoms in the shown centrosymmetric molecule (blue, C; deep blue, N; grey, H) which contains two imidazole moieties, poses the possibility of the coexistence of three tautomers in the solid state. The observed and theoretical [from B3LYP/6-311+G(2d,p) calculations] H-bonding pattern indicate that only two tautomers are present in the solid state.