Synthesis, spectroscopic, and structural aspects of two trinuclear cyano-bridged heterometallic complexes

Two new cyano-bridged trinuclear heterometallic complexes [Sr₂(Phen)₄(CF₃CO₂)(H₂O)₃Fe(CN)₆]·2H₂O (1) [Ca₂(Phen)₄(CF₃CO₂)(H₂O)Co(CN)₆]·2H₂O (2) (where Phen=1,10-phenanthroline) have been synthesized and their crystal structures have been determined. The structure of complex (1) features a central [Fe(CN)₆]³⁻ unit that links a monocation, [Sr(Phen)₂(OH₂)(OOCCF₃)]⁺ and a dication, [Sr(Phen)₂(OH₂)₂]²⁺ via two trans cyanide bridges. The complex (2) features a central [Co(CN)₆]³⁻ unit that links two monocations of [Ca(Phen)₂(OH₂)(OOCCF₃)]⁺ (the positions of the trifluoro acetate and water molecules are disordered over two positions) via two trans cyanide bridges. Each metal atom is seven coordinated and achieves pentagonal bipyramidal geometry. Two cocrystallized water molecules are present in both the complexes. The presence of an extensive network of hydrogen bonding imparts the overall stability to both the systems.     

Direct flame atomic absorption spectrophotometric determination of alkalis in geochemical samples

Flame atomic absorption spectrometry has been used for the estimation of the alkali metal content (as Na₂O and K₂O) in 95 reference materials with diverse matrices (including recently introduced Polish and Chinese standard samples awaiting certification through collaborative studies) using 1000 μg ml⁻¹ of lanthanum and 2000 μg ml⁻¹ of rubidium as matrix buffers for sodium and potassium, respectively. The ±t (Student's values for the samples with known recommended values (degree of freedom n − 1 = 9), at the 95% and 99% confidence levels) indicate that within the confidence levels 95–99% there is no statistical difference between the data presented and the reference data for most of the samples. The agreement between the reported data and the results obtained are generally good.     

Crystal structure of aluminium containing superconducting oxides: single crystal study of GdBa2Cu3−x AL x O6.88 (x=0.28) and ErBa2Cu3−y Al y O6.6 (y=0.14)

Following the discovery of the high temperature super-conductivity in YBa₂Cu₃O_7– (T _c 93 K) [1] it has been found that Y atoms can be substituted entirely by almost all of the rare-earth elements, except for Ce, Pr, and Tb, without changing the superconducting properties appreciably [2, 3]. The magnetic moments carried by the rare-earth atoms have apparently no influence on the superconducting properties. In Nd-, Sm-, Gd-, Dy- and Er-based compounds the rare earth moments order at low temperatures (0.025–2.2 K) [4–8] and the ordered antiferromagnetic state coexists with the superconducting state. We have investigated the antiferromagnetic ordering of these compounds by neutron diffraction both on powder and single crystal samples obtained from several laboratories [8–10]. Magnetic structures of all these compounds consist of antiferromagnetic (001) planes stacked ferro- or antiferromagnetically. There have been some controversies as to the stacking of antiferromagnetic (001) planes in GdBa₂Cu₃O_7–.     

Synthesis of Au nanoparticle-conductive polyaniline composite using H2O2 as oxidising as well as reducing agent

We report a new method of synthesis of an Au nanoparticle-conductive polyaniline composite by using H2O2 both for reduction of HAuCl4 and polymerization of aniline in the same aqueous medium: the electrical conductivity of the composite has been measured to be two orders of magnitude higher than the polymer itself.     

Absorption spectroscopic study of EDA complexes of

[70]Fullerene has been shown to form 1:1 molecular complexes with toluene, p-xylene, m-xylene, 1,2,4,5-tetramethyl benzene (durene) and pentamethyl benzene (PMB) in CCl4 medium by absorption spectroscopic method. Isosbestic points have been detected in case of complexes with PMB and durene. Charge transfer absorption band could not be detected but the intensity of the broad absorption band of C70 in CCl4 decreases systematically with increase in the concentration of the added methylbenzenes. From this trend the formation constants (Kc) of the complexes have been determined at three different wavelengths. The constancy of Kc with respect to change in the wavelength of measurement supports the view that complex of a single stoichiometry (1:1) is formed in each case.     

Thermodynamic stability of the γ-Co1−x Se phase by CaF2 electrolyte galvanic cell method

The partial molar free enthalpy of cobalt, , and the molar free enthalpy of formation of Co _x Se alloy phase, G _f ⁰ (Co _x Se) at 873K, were determined by the solid CaF₂ electrolyte galvanic cell method forx=0.725 to 0.956. was observed to be a monotonic function of the mole fractionX _Co in the composition region of the investigation with an inflexion point atX _Co=0.455. The measurements were extended down to a temperature of 710 K and a partial Co–Se phase diagram was evaluated from the resultant data.

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Untersuchung der thermodynamischen Stabilität der -Co-_1–x Se Phase mittels galvanischer Zelle mit CaF₂ Elektrolyt

Zusammenfassung Die partiellen molaren freien Enthalpien von Kobalt ( ) und die molaren freien Bildungsenthalpien der Co _x Se Legierungsphase [G f/0 (Co _x Se) bei 873 K] wurden mittels galvanischer Zelle (CaF₂ Fest-Elektrolyt) fürx=0,725–0,956 bestimmt. wurde im untersuchten Bereich als monotone Funktion vom MolenbruchX _Co, mit einer Inflexion beiX=0,455, gefunden. Die Messungen wurden bis zu einer Temperatur von 710 K ausgedehnt und die Daten wurden zur Erstellung eines partiellen Co–Se-Phasendiagramms ausgewertet.

     

Spectroscopic investigation on the interaction of ICT probe 3-acetyl-4-oxo-6,7-dihydro-12H Indolo-[2,3-a] quinolizine with serum albumins

Interaction of 3-acetyl-4-oxo-6,7-dihydro-12H indolo-[2,3-a] quinolizine (AODIQ), a biologically active molecule, with model transport proteins, bovine serum albumin (BSA) and human serum albumin (HSA) have been studied using steady state and picosecond time-resolved fluorescence and fluorescence anisotropy. The polarity dependent intramolecular charge transfer (ICT) process is responsible for the remarkable sensitivity of this biological fluorophore to the protein environments. The CT fluorescence exhibits appreciable hypsochromic shift along with an enhancement in the fluorescence yield, fluorescence anisotropy (r) and fluorescence lifetime upon binding with the proteins. The reduction in the rate of ICT within the hydrophobic interior of albumins leads to an increase in the fluorescence yield and lifetime. Marked increase in the fluorescence anisotropy indicates that the probe molecule is located in a motionally constrained environment within the proteins. Micropolarities in the two proteinous environments have been determined following the polarity sensitivity of the CT emission. Addition of urea to the protein-bound systems leads to a reduction in the fluorescence anisotropy indicating the denaturation of the proteins. Polarity measurements and fluorescence resonance energy transfer (FRET) studies throw light in assessing the location of the fluorophore within the two proteinous media.     

Crystal engineering with aroyl hydrazones of diacetyl monooxime – Molecular and supramolecular structures of two Ni(II) and two Zn(II) complexes

Four new Schiff bases of aroyl hydrazides with diacetyl monooxime have been prepared, and Ni(II) and Zn(II) complexes of these ligands have been synthesized. Two Ni(II) and two Zn(II) complexes have been characterized by X-ray crystallography. The aroyl hydrazone ligands were designed in such a way that there is a systematic variation in the H-bond forming abilities of their aroyl moiety, e.g. both H-bond acceptor and donor (salicyloyl), only H-bond donor (anthraniloyl), only H-bond acceptor (isonicotinoyl). It is shown in this work that such a variation in the H-bond donor acceptor properties of the ligands leads to considerable diversity in their supramolecular architecture.     

NMR spectrometric studies of complexation of [60]fullerene with series of anisoles

Detailed (1)H and (13)C NMR spectrometric studies have been carried out to gain insight into the nature of molecular interactions of the electron donor-acceptor (EDA) complexes of [60]fullerene with a series of anisoles, namely, anisole, m-bromoanisole, and p-bromoanisole. [60]Fullerene has been shown to form 1:1 adducts with the above series of anisoles. Formation constants (K) for all the complexes have been determined from the systematic variation of the NMR chemical shifts of specific protons of the anisoles in the presence of [60]fullerene. The K values of [60]fullerene/anisole, [60]fullerene/m-bromoanisole, and [60]fullerene/ p-bromoanisole complexes yield good estimates of the Hammett rho constant for the complexation reaction. To the best of our knowledge, this paper reports for the first time a very fruitful technique by which the concentrations of EDA complexes can be estimated from systematic variations of the (13)C NMR signal.     

Optimal use of instrumental neutron and photon activation analyses for multielement determinations in sewage sludges

A combination of instrumental neutron activation analysis (INAA) and instrumental photon activation analysis (IPAA) methods has been developed for multielement determinations in a variety of sludges and fertilizers. The precision and accuracy of both the methods have been evaluated by analyzing replicate samples, NBS standard reference materials, and an interlaboratory intercomparison sewage sludge sample. The concentration rages of up to 50 elements in raw and chemical sludges, sludge-based fertilizers, and other organic and inorganic fertilizers are reported here. The advantages and limitations of the INAA and IPAA methods are also discussed here.