A novel discrete dinuclear copper(II)–gadolinium(III) complex derived from a Schiff base ligand [Cu(salbn)Gd(NO3)3·H2O] (salbn): N,N′-butylenebis(salicylideaminato)

The synthesis, X-ray and e.p.r. spectral studies of a 3d–4f couple are described here. The crystal structure of [Cu(salbn)Gd(NO₃)₃·H₂O], (2), salbn = N,N-butylenebis(salicylideaminato), has been determined by X-ray crystallography. Compound (2) crystallizes in the monoclinic system, space group p21/n, with a = 9.025(1), b = 22.912(1), c = 12.790(1) Å, = 99.36(1), Z = 4. The deviations of the four coordinating atoms (O(1)O(2)N(1) and N(2) of salbn and the copper atom is displaced from the plane in spite of the lack of any apical ligand. The gadolinium(III) ion is nine-coordinated by the two oxygen atoms of the salbn moiety, three bidentate nitrate ions and one water molecule. The geometry of Gd^III can be described as a square antiprism, in which compound Cu^II and Gd^III are bridged by the two phenolic oxygens of salbn. The Cu^II–Gd^III distance is 3.269(1) Å. The bridging core CuO2Gd is a butterfly shape. Significant distortion was observed for the complex having the larger diamino string. The title compound exhibits seven e.s.r. transitions with |D| = 0.0467 cm^–1, which demonstrates the existence of zero field splitting. This outcome indicates that compound (2) consists of a perfectly isolated dinuclear Cu–Gd core and steric bulk alters the dihedral angle in the Cu–O–Gd bridge.     

Single crystal EPR study of VO(II)-doped magnesium potassium Tutton’s salt — Part 4

Single crystal EPR studies of VO(II)-doped magnesium potassium Tutton’s salt have been carried out at room temperature. The results indicate that the paramagnetic impurity has entered the lattice, both substitutionally and interstitially and the maximum hyperfine for the substitutional site along the a axis corresponds to the minimum hyperfine for interstitial site and vice versa. The spin Hamiltonian parameters obtained from single crystal data for these sites are: Site 1, g_||=1.954(1); g=1.998(1), A_||=19.80(2) mT; A=7.61(2) mT; Site 2, g_||=1.997(1); g=1.952(1), A_||=7.66(2) mT; A=19.85(2) mT. Superhyperfine from ligand protons have been observed at certain orientations for Site 2 impurity. Powder spectrum shows a set of eight parallel and perpendicular features indicating the presence of only one site and these values matched with Site 1 values. From these observations, it has been concluded that the two vanadyl impurities are approximately at right angles to each other. Cooling the sample to 77 K does not change the spectra appreciably. The admixture coefficients have been calculated from Site 1 data, which agree well with the reported values.     

Characterization of partially transesterified poly(beta-hydroxyalkanoate)s using matrix-assisted laser desorption/ionization time-of-flight mass spectrometry

Matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOFMS) was used for the characterization of a partially transesterified poly(beta-hydroxyalkanoate), PHA, polymer produced by the bacterial strain Alcaligenes eutrophus using saponified vegetable oils as the sole carbon sources. The transesterification was carried out separately under acidic and basic conditions to obtain PHA oligomers weighing less than 10 kDa. The intact oligomers were detected in their cationized [M + Na](+) and [M + K](+) forms by MALDI-TOFMS. A composition analysis, using the MALDI-TOF spectra, indicate that the oligomers obtained via acid catalysis were terminated with a methyl 3-hydroxybutyrate end group, and those obtained by base catalysis had a methyl crotonate (olefinic) termination. In addition to HB (hydroxy butyrate), the oligomers were found to contain a small percentage of HV (hydroxy valerate). This was independently confirmed using gas chromatography/mass spectrometry (GC/MS). In comparison, the analysis of a commercial PHA polymer, transesterified under identical conditions, only showed the presence of HB, i.e. a pure PHB homopolymer. Copyright 1999 John Wiley & Sons, Ltd.     

Spectral Studies on VO2+ doped MPPH Crystals

Magnesium Potassium Phosphate Hexahydrate (MPPH), is analogous to the bio‐mineral struvite. Vanadyl doped MPPH crystals are grown by slow evaporation technique. EPR and optical absorption studies are carried out at room and liquid nitrogen temperatures. Spin‐Hamiltonian, crystal field and bonding parameters are evaluated.     

Infrared and ab initio studies on 1,2,4,5-tetrafluorobenzene clusters with methanol and 2,2,2-trifluoroethanol: presence and absence of an aromatic C-H...O hydrogen bond

The (1:1) clusters of 1,2,4,5-tetrafluorobenzene (TFB) with methanol and with 2,2,2-trifluoroethanol (TFE) were studied both experimentally and computationally. Through use of fluorescence-detected infrared spectroscopy, the (1:1) clusters were identified in supersonic jets. Intermolecular interactions in the clusters were characterized by the spectral shifts of the aromatic C-H stretching modes in the TFB moiety owing to the cluster formation. The molecular structures, stabilization energies, and vibrational frequencies of the clusters were computed at the MP2/6-31+G level. Both computational and experimental data indicate that an aromatic C-H...O hydrogen bond is present in the TFB-methanol cluster, while it is absent in the TFB-TFE cluster.     

Tensammetric studies on corrosion inhibitors

The study of adsorption by the alternating current polarographic method is known as ‘tensammetry’. This technique has been extended to the study of the adsorption characteristics of organic corrosion inhibitors with a view to elucidate the mechanism of inhibition by such compounds. The usefulness of such studies in elucidating the mechanism of inhibition by dicyclohexylamine nitrite, which is now widely used as a vapour phase corrosion inhibitor, is brought out. For this purpose, results obtained by tensammetric studies have been compared with potential measurements on the one hand and direct corrosion tests on the other and discussed.     

Co-occurrence of superparamagnetism and anomalous hall effect in highly reduced cobalt-doped rutile TiO2-delta films

We report a detailed magnetic and structural analysis of highly reduced Co doped rutile TiO(2-delta) films displaying an anomalous Hall effect (AHE). The temperature and field dependence of magnetization, and transmission electron microscopy, clearly establish the presence of nanosized superparamagnetic cobalt clusters of approximately 8-10 nm size in the films at the interface. The co-occurrence of superparamagnetism and AHE raises questions regarding the use of the AHE as a test of the intrinsic nature of ferromagnetism in diluted magnetic semiconductors.