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.     

Total synthesis of (+)-blastmycinone and formal synthesis of (+)-antimycin A3b

The formal synthesis of (+)-antimycin A_3b and the total synthesis of (+)-blastmycinone were achieved using, as a key step, a method developed by us for the synthesis of 2-methyl-1,3-diols via Ti(III)-mediated diastereo- and regioselective opening of trisubstituted 2,3-epoxy alcohols, to carry out the stereoselective construction of the hydroxy-acid segment. An interesting intramolecular radical translocation took place during the epoxide opening process transforming its vicinal PMB-ether in situ, into an ‘1,2-O-(p-methoxy)benzylidene’ ring.     

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.     

Influence of ester and ether linkage in phospholipids on the environment and dynamics of the membrane interface: a wavelength-selective fluorescence approach

We have monitored the environment and dynamics of the membrane interface formed by the ester-linked phospholipid 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) and the ether-linked phospholipid 1,2-dihexadecyl-sn-glycero-3-phosphocholine (DHPC) utilizing the wavelength-selective fluorescence approach and using the fluorescent membrane probe 2-(9-anthroyloxy)stearic acid (2-AS). This interfacially localized probe offers a number of advantages over those which lack a fixed location in the membrane. When incorporated in membranes formed by DPPC and DHPC, 2-AS exhibits red edge excitation shift (REES) of 14 and 8 nm, respectively. This implies that the rate of solvent reorientation, as sensed by the interfacial anthroyloxy probe, in ester-linked DPPC membranes is slow compared to the rate of solvent reorientation in ether-linked DHPC membranes. In addition, the fluorescence polarization values of 2-AS are found to be higher in DHPC membranes than in DPPC membranes. This is further supported by wavelength-dependent changes in fluorescence polarization and lifetime. Taken together, these results are useful in understanding the role of interfacial chemistry on membrane physical properties.     

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.

     

Solid state Mössbauer,e.p.r., magnetic properties and thermally induced stereochemical studies on double complex salts of cyclic diamine containing cationic copper(II) complexes and a hexacyanoferrate(III) anion

Summary Double complex salts containing cationic Cu^II having cyclic ligand piperazine (pipz), N-methylpiperazine (mpipz) and N,N-dimethylpiperazine (dmpipz) and hexacyanoferrate(III) ion have been synthesized and characterized by elemental analyses, i.r. and electronic spectra, and magnetic moment measurements. Mössbauer spectra at room temperature and at 80 K, were recorded in order to evaluate the metal-metal charge transfer and the impact of the cyclic ligand present in cationic moiety of the double complex salt upon the Mössbauer spectra of the hexacyanoferrate(III) ion. Evidence for metal-metal charge transfer is supported by electronic spectra and magnetic susceptibilities. Variable temperature e.p.r. spectra were recorded in order to determine the distortion of crystal system. Thermally induced stereochemical studies have been carried out with the help of i.r. spectral data. Kinetics of thermochemical reactions have also been studied. Activation energies (E _infa ^sup* ) and inception temperatures for the thermochemical reactions show the order of stability of the double complex salts follows the trend: dmpipz > mpipz > pipz, which indicates that the + I effect is more pronounced than steric effect.     

Effect of Al doping on the conductivity type inversion and electro-optical properties of SnO2 thin films synthesized by sol-gel technique

Al doped SnO₂ thin films have been synthesized by a sol-gel dip coating technique with different percentages of Al on glass and silicon substrates. X-ray diffraction studies confirmed the proper phase formation in the films and atomic percentage of aluminium doping in the films was obtained by energy dispersive X-ray studies. SEM studies showed the particle sizes lying in the range 100–150 nm for the undoped films and it decreased with increase of Al doping. Optical transmittance spectra of the films showed high transparency (∼80%) in the visible region and the transparency increases with the increase of Al doping in the films. The direct allowed bandgap of the films have been measured for different Al concentration and they lie within the range of 3.87–4.21 eV. FTIR studies depicted the presence of Sn–O, Al–O, bonding within the films. The room temperature electrical conductivities of the films are obtained in the range of 0.21 S cm⁻¹ to 1.36 S cm⁻¹ for variation of Al doping in the films 2.31–18.56%. Room temperature Seebeck coefficients, S_RT of the films were found in the range +56.0 μVK⁻¹ to −23.3 μVK⁻¹ for variation of Al doping in the films 18.56–8.16%. It is observed that the Seebeck coefficient changes its sign at 12.05% of Al in the films indicating that below 12.05% of Al doping, SnO₂:Al behaves as an n-type material and above this percentage it is a p-type material.