Complexometric titration of gallium, indium and thallium(III) using sodium azide as a metal indicator

Summary Thallium(III) has been determined between pH 4.0 and 6.0 by titration against EDTA using sodium azide as indicator. The metal ion gives a bright yellow colour which is discharged at the equivalence point. Micro-quantities upto about 1 mg of the metal have been determined with accuracy. The end-point has also been determined photometrically. Gallium(III) and indium(III) can also be determined by back-titration of the excess of EDTA added to each of these ions against a standard ferric chloride solution using sodium azide as indicator.

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Zusammenfassung Thallium(III) wird durch Titration mit ÄDTA-Lösung bei pH 4,0–6,0 gegen Natriumazid als Indicator bestimmt. Der Umschlag am Endpunkt erfolgt von Gelb nach Farblos. Mikromengen bis zu 1 mg können mit guter Genauigkeit erfa\t werden. Die Bestimmung kann auch photometrisch durchgeführt werden. Gallium(III) und Indium(III) können durch Rücktitration von überschüssigem ÄDTA mit Eisen(III)-chloridlösung bestimmt werden, wobei ebenfalls Natriumazid als Indicator dient.

     

Complex Formation of Ytterbium (III) with Bromopyrogallol Red—A Spectrophotometric Study

The complex formation of Ytterbium (III) with Bromopyrogallol red has been studied. spectrophotometrically in an attempt to establish composition, stability, thermodynamic parameters and optimum conditions for determining small amounts of ytterbium. The violet complex of ytterbium has λ_max at 620nm against a reagent blank. The composition determined by different methods is 1:1 at pH 6.2±0.1. The mean value of log K, free energy (ΔG), the heat content (ΔH) and entropy (ΔS) changes, of the complex are found to be 6.0, —8.1.kcal/mole, —3.5 Kcal/mole and 15.53 e.U. respectively at 30°C. The net molar absorptivity and Sandell's sensitivity is 19850 and 0.0087 μg of ytterbium /cm². The effect of diverse ions was examined with thirteen cations and ten anions in the determination of ytterbium.     

Studies ono-hydroxyacetophenone-2-furoylhydrazone complexes of some 3d-bivalent metal ions

Summary Complexes ofo-hydroxyacetophenone-2-furoylhydrazone, H₂L, of the types M(H₂L)C1₂ · nH₂O [Mn = Co^II, n=0; Ni^II, n=2]; Cu(HL)Cl, M(HL)₂ [M = V^IVO, Co^II, Ni^II or Cu^II] and M(L)(H₂O)_n [M = Co^II or Ni^II, n=2; M = Cu^II, n=0] have been prepared and characterized by elemental analyses, molar conductance, magnetic susceptibility, visible, e.s.r. and i.r. spectral studies. The different modes of ligand chelation and the stereochemistry around the metal ions are discussed.     

TLC separation of some inorganic ions on diethylenetriamine impregnated layers

Summary A suitable TLC method for the separation of Co, Zn, Ni, As, Pb, Cd, Hg, Ag, Th, Se, Sn(IV), Fe(II), U, V, Cu, Ti, Zr and Sb on silica gel impregnated with diethylenetriamine and using ethanol-acetone-acetic acid (70∶50∶20) or (40∶50∶20) as solvent systems and employing 1% K₄Fe(CN)₆ or 0.5% dithizone as visualisation reagents has been developed.     

Protein surface-assisted enhancement in the binding affinity of an inhibitor for recombinant human carbonic anhydrase-II

We elaborate on a novel strategy for enhancing the binding affinity of an active-site directed inhibitor by attaching a tether group, designed to interact with the surface-exposed histidine residue(s) of enzymes. In this approach, we have utilized the recombinant form of human carbonic anhydrase-II (hCA-II) as the enzyme source and benzenesulfonamide and its derivatives as inhibitors. The steady-state kinetic and the ligand binding data revealed that the attachment of iminodiacetate (IDA)-Cu(2+) to benzenesulfonamide (via a triethylene glycol spacer) enhanced its binding affinity for hCA-II by about 40-fold. No energetic contribution of either IDA or triethylene glycol spacer was found (at least in the ground state of the enzyme-inhibitor complex) when Cu(2+) was stripped off from the tether group-conjugated sulfonamide derivative. Arguments are presented that the overall strategy of enhancing the binding affinities of known inhibitors by attaching the IDA-Cu(2+) groups to interact with the surface-exposed histidine residues will find a general application in designing the isozyme-specific inhibitors as potential drugs.     

Thermal behaviour of copper oxalate and its mixed ligand complexes with amines

The thermal decomposition behaviour of copper oxalate hemihydrate and its complexes with different amines has been studied by TG and DTA methods in nitrogen and air atmospheres. The complexes CuC₂O4 · 0.5 H₂O, CuC₂O₄(NH₃)₂ and CuC₂O₄(py) produced Cu₂O as final residue after decomposition, whereas, another group of complexes, CuC₂O₄(EtNH₂)₂, CuC₂O₄(MeNH₂)₂, CuC₂O₄(en)₂ and CuC₂O₄(An)₂, gave a final residue of CuO. All the complexes decomposed without forming any isolable stable intermediate; an exception was CuC₂O₄(en)₂, which formed a binuclear intermediate complex, [CuC₂O₄en]₂.     

Physico-chemical behaviour of the carbonate rocks of Western Son Valley Region,India

The techniques of DTA and TG were employed to study the thermal characteristics of unfossiliferous carbonate litho-units, viz. Fawn dolomitic limestone (microdolsparite) and Rohtas limestone (micrite) belonging to the Vindhyan Supergroup (PreCambrian) of India. The DTA of Fawn dolomitic limestone displayed two successive endothermic peaks at 725° and 860° whereas only one endothermic change at 910° was recorded in the DTA curve of Rohtas limestone. It was confirmed by chemical analyses, TG, IR and X-ray diffraction studies that the two peaks in the first case are due to dissociation of CO₂ from magnesium and calcium lattice positions, while the sole peak in the second case is due to complete decarbonation. A tentative correlation between the thermal characteristics and structural changes of these carbonate rocks at various transition temperatures is presented.     

Tetrakisisopropoxy tantalum(V)O,O′-alkylene dithiophosphate complexes

Summary Tetrakisisopropoxytantalum(V) alkylene dithiophosphato complexes, (G=–CMe₂CMe₂–, –CHMeCHMe–, –CH₂CMe₂CH₂– and –CH₂CEt₂CH₂–) have been prepared from equimolar ratios of tantalum(V) isopropoxide and alkylene dithiophosphoric acids in benzene. These moisture-sensitive compounds, which are soluble in common organic solvents and are monomeric, have been characterized by elemental analysis, molecular weight determinations and by their i.r. and n.m.r. spectra. An octahedral geometry is suggested in which the ligand is bidentate.     

Telluranes: potential synthons for charge-transfer complexes (involving hypervalent Te-I bonds) and serendipitous synthesis of the first triphenyl methyl phosphonium salts containing [C4H8TeI4] and [TeI6]anions

Hypervalent Te-I bonds of telluranes (C₄H₈TeI₂, C₅H₁₀TeI₂ and α-Me₂TeI₂) have been utilised to form the charge transfer (CT) complexes (1-3). The reaction of cyclic tellurane (1,1-diiodotetrahydro tellurophene, C₄H₈TeI₂) with I₂/ICl yields C₈H₁₆Te₂I₆ [IC₄H₈TeI-I-I-ITeC₄H₈I] (1); an unusual dinuclear species while the reaction of another cyclic tellurane (1,1-diiodo telluracyclohexane, C₅H₁₀TeI₂) with I₂ yields C₅H₁₀TeI₄ (2) possessing different structural motif than 1. In 2 the iodine molecules are on both sides bonded to iodine atom of hypervalent Te-I bond of C₅H₁₀TeI₂ which is analogous to the structural type present in Me₂TeI₄ (3) obtained by the reaction of α-Me₂TeI₂ with ICl. The reaction of C₄H₈TeI₂ with PPh₃, serendipitously, yields the first triphenyl methyl phosphonium salts [PPh₃Me]₂ ²⁺[C₄H₈TeI₄]²⁻ (4) and [PPh₃Me]₂ ²⁺[TeI₆]²⁻ (5), indicating the oxidation of PPh₃ whereas C₄H₈TeI₂ itself, is converted into [C₄H₈TeI₄]²⁻ and [TeI₆]²⁻ anions. All the complexes 1-5 have been characterised through single crystal X-ray diffraction studies.