The reactivity of the cis-RuCl2 fragment in Ru(P)2(TaiMe)Cl2 with N,O; O,O and S,S-chelators (P = PPh3; TaiMe = 1-methyl-2-(p-tolylazo)imidazole)

Ru(P)₂(TaiMe)Cl₂ [P = PPh₃; TaiMe = 1-methyl-2-(p-tolylazo)imidazole] possesses a cis-RuCl₂ configuration. Dechlorination was carried out in acetone solution by Ag⁺ and the solvated species reacted with N,O-[oxinate (ox), -picolinate (pic)], O,O-[salicylate (sa), 3-formylsalicylate (3-fsa), 5-formylsalicylate (5-fsa)] and S,S-[xanthate (xan), dithiocarbamate (dtc)] chelators to yield [Ru(P)₂(TaiMe)(N,O/O,O/S,S)] (ClO₄) _n (n = 1 for N,O- and S,S-chelators; n = 0 for O,O-chelators). The complexes were characterised by microanalysis, molar conductance, i.r., u.v.–vis. and ¹H-n.m.r. data. Isomeric structures in some complexes were identified by ¹H-n.m.r. spectra. The electronic spectra show a high intensity ( 10⁴) m.l.c.t. transition in the visible region together with a weak shoulder ( 10³) at longer wavelength. Redox studies exhibit a Ru^III/Ru^II couple and quasireversible azo reduction.     

Isoelectric focusing in long immobilized pH gradient gels to improve protein separation in proteomic analysis.

The number of protein spots detected on two-dimensional polyacrylamide gel electrophoresis (2-D PAGE) gels increases as the gel size increases. The largest commercially available systems resolve a few thousand spots, being only a fraction of the total proteome. We have developed an extremely long isoelectric focusing (IEF) system aimed at more complete protein profiling. The system is especially well suited to sensitive detection methods, such as radioactive detection. The major constraint preventing progress in this area has been the inability to create an even density gradient during the immobilized pH gradient (IPG) casting process. We demonstrate for the first time that this constraint can be effectively overcome, to enable greatly increased IEF separating power with all the advantages of IPG technology,     

Synthesis,spectral characterization and redox studies of [1-alkyl-2-(naphthyl-β-azo)imidazole] palladium(II) catecholates

1-Alkyl-2-(naphthyl--azo)imidazoles [-NaiR; R = Me (a), Et (b), CH₂Ph (c)] react with Pd(MeCN)₂Cl₂ to yield Pd(-NaiR)Cl₂ (2), the i.r. spectra of which support the presence of a cis-PdCl₂ configuration. The complexes react with catechols in the presence of Et₃N to yield ternary complexes [Pd(-NaiR)(O,O)] [O,O = pyrocatecholato (cat) (3), 4-t-butylcatecholato (tbcat) (4), 3,5-di-t-butylcatecholato (dtbcat) (5), and tetrachlorocatecholato (tccat) (6)], which were characterized by elemental analysis, i.r. and ¹H-n.m.r. spectral data. Redox studies by cyclic voltammetry suggest the existence of four successive redox couples wherein two responses, positive to s.c.e. are due to catechol to semiquinone and semiquinone to quinone oxidation, respectively; the couples at negative to s.c.e. are referred to azo reductions. The complexes exhibit ligand-ligand charge-transfer transitions in the near-i.r. region. The band position is largely dependent upon the substitutent on the catechol frame and exhibits negative solvatochromic effects. The transition is qualitatively assigned as the HOMO (cat) LUMO (-NaiR) transition. This fact is also supported by theoretical calculations using the PM3 method.     

Naphthyl-(2-pyridylmethylene)amine complexes of silver(I) and ruthenium(II): synthesis,spectral studies and electrochemical behaviour

Pyridine-2-carboxaldehyde reacts with /-naphthylamine to give /-naphthyl-(2-pyridylmethylene)amine [-L (1), -L (2)]. L belongs to the unsymmetric diimine (—N=C—C=N—) family which can form five–membered chelate rings with metal ions. {donor centers are abbreviated as N[N(Py)] and N [N(nap)]} [Ag(L)₂]⁺ complexes were prepared and characterized by spectroscopic data. The reaction between L and RuCl₃ in boiling EtOH yielded green and blue–green compounds of composition RuCl₂(L)₂. I.r., u.v.–vis. and ¹H-n.m.r. data determined the stereochemistry of the complexes as trans-cis-cis (green) and cis-trans-cis (blue–green) according to the sequence of the coordination pair of Cl, N [N(Py)] and N [N(nap)]. Upon treatment of Ag(L)₂ ⁺ with Ru(bpy)₂Cl₂ in alcoholic suspension the ternary complexes, [Ru(bpy)₂(L)](ClO₄)₂, were isolated and characterized by spectroscopic data. [Ru(bpy)(L)₂](ClO₄)₂ complexes were synthesized similarly from ctc-Ru(L)₂Cl₂ and 2,2-bipyridine (bpy) in the presence of AgNO₃ and NaClO₄. These complexes show well-defined m.l.c.t transitions in the visible region. The sterochemistry of the complexes was established by ¹H-n.m.r. data. Cyclic voltammetry shows a high potential Ru^III/Ru^II couple and follows the order: [Ru(bpy)(L)₂]²⁺ > [Ru(bpy)₂(L)]²⁺ > Ru(-L)₂Cl₂ > Ru(-L)₂Cl₂.     

Chemometric data analysis of pollutants in wastewater—a case study

In this study, chemometric techniques such as cluster analysis (CA), discriminant analysis (DA), principal component analysis (PCA) and partial least squares (PLS) were used to analyse the wastewater dataset to identify the factors which affect the composition of sewage of domestic origin, spatial and temporal variations, similarity/dissimilarity among the wastewater characteristics of cis- and trans-drains and discriminating variables. Samples collected from 24 wastewater drains in Lucknow city and from three sites on Gomti river in the month of January/February, May, August and November during the period of 5 years (1994-1999) were characterized for 32 parameters. The multivariate techniques successfully described the similarities/dissimilarities among the sewage drains on the basis of their wastewater characteristics and sources signifying the effect of routine domestic/commercial activities in respective drainage areas. Spatial and seasonal variations in wastewater composition were also determined successfully. CA generated six groups of drains on the basis of similar wastewater characteristic. PCA provided information on seasonal influence and compositional differences in sewage generated by domestic and industrial waste dominated drains and showed that drains influenced by mixed industrial effluents have high organic pollution load. DA rendered six variables (TDS, alkalinity, F, TKN, Cd and Cr) discriminating between cis- and trans-drains. PLS-DA showed dominance of Cd, Cr, NO₃, PO₄ and F in cis-drains wastewater. The results suggest that biological-process based STPs could treat wastewater both from the cis- as well as trans-drains, however, prior removal of toxic metals will be required from the cis-drains sewage. Further, seasonal variations in wastewater composition and pollution load could be the guiding factor for determining the STPs design parameters. The information generated would be useful in selection of process type and in designing of the proposed sewage treatment plants (STPs) for safe disposal of wastewater.     

Three-dimensional mesoporous titanosilicates prepared by modified sol-gel method: Ideal gold catalyst supports for enhanced propene epoxidation

Mesoporous titanosilicates with 1-12 mol % Ti content and with three-dimensional wormhole-like mesoporosity are prepared by a modified sol-gel technique. Sorption analysis shows that there is little change in the surface properties with increasing Ti concentration in the samples, implying that Ti atoms either are well-dispersed on the walls of the silica matrix or are present inside the framework with no pore blocking effect. Spectroscopic analysis shows that the Ti atoms are atomically dispersed in the silica matrix even at very high Ti concentration and there is no observable Ti aggregate (anatase) present in the samples. These titanosilicate samples after Au deposition followed by trimethylsilylation (for enhanced hydrophobicity) are highly efficient catalysts for vapor-phase propene epoxidation using O2 and H2. It was possible to achieve commercially desirable performance with about 7% propene conversion, >90% propene oxide selectivity, and about 40% hydrogen efficiency.     

Synthesis and characterization of cobalt(II), nickel(II), copper(II), palladium(II) and dioxouranium(VI) complexes of the antipyrine Schiff base of 3-formylsalicylic acid

A new Schiff base has been synthesized from 4-aminoantipyrine and 3-formylsalicylic acid. The ligand has a dianionic tetradentate compartmental OONO donor system. The cobalt(II), nickel(II), copper(II) and dioxouranium(VI) complexes exist in phenolato-bridged dinuclear species, while palladium(II) gives a mononuclear complex with free –COOH groups. The complexes have been characterized by elemental analyses, i.r., u.v.-vis, thermal and magnetic measurements.