Wahid U. Malik

Preparation and characterisation of copper, cobalt and nickel complexes of tetradentate N6 macrocyclic ligand

Abstract Macrocyclic complexes of copper, nickel and cobalt were synthesised via template reactions. These 14-membered N6 tetradentate macrocyclic complexes were characterised by magnetic, conductance, electronic and IR spectral studies. The macrocyclic ligand coordinates through the four azomethine nitrogen atoms which are bridged by 2,3-butanedione, moieties, but far IR spectra suggest that the pyridine nitrogens are not coordinated. These macrocyclic complexes are considered to have distorted octahedral configurations.

Studies in the membrane permeability of chromic ferro and ferricyanides

Abstract The permeability of various electrolytes (with a common cation) through parchment-supported chromic ferro- and ferricyanide membranes was investigated, employing the constant flow method. The permeability order was found to be Cl− > Br > NO3− > CNS− > CH3COO− > SO4= > FeCy6=− > FeCy6== in both cases. A considerable decrease in these values was observed when potassium ferro- and ferricyanide treated membranes were used. Adsorption and membrane potential studies revealed an order that was just the reverse of that for permeability. The energy of activation for the diffusion process for various electrolytes was found to lie between 5000 and 6500 calories per mole, values which are higher than those determined for the free diffusion of electrolytes. The role of Hofmeister series has been considered in relation to the peptizing of the membrane material during the diffusion process and such peptizing appears to be one of the factors controlling the permeability phenomenon.

Hydrogen ion equilibria of transfusion gelatin

Hydrogen ion equilibria studies of transfusion gelatin carried out at different temperatures revealed the presence of 84 carboxyl, 23 amino, 3–8 imidazole and 43 guanidinium groups per 75·103 g of the protein. The results confirmed the values of amino acid analysis and also those obtained from observations of apparent heats of ionsation. Tanfords equation was found in this case to be applicable only in the carboxyl region, (W = 0.027). Further work regarding the interaction of cations, other than hydrogen ions, with transfusion gelatin is in progress.

Preparation and characterisation of some new 12- and 14-membered dibenzotetraaza macrocyclic complexes of iron(III)

The iron(III) macrocyclic complexes of some 12- and 14-membered dibenzo tetraaza macrocycles have been synthesised by the template process using o-phenylenediamine and the appropriate diketone. This affords a method to prepare these complexes with different ring substituents and varying degrees of unsaturation. All complexes were characterised by elemental analysis, molar conductance, magnetic susceptibility, visible and infrared spectra. They are all high spin and six coordinate. These macrocycles tend to attain a ‘saddle shape’ which favours a cis-geometry. This is supported by the infrared and Mossbauer spectra.

Polarographic reduction of some potential antineoplastic compounds

Summary Polarographic reduction of 1-thiocarbamoyl-3,5-dimethyl-4-substituted arylazopyrazoles and 1-thiocarbamoyl-3,5-diphenyl-4-substituted arylazopyrazoles gives well-defined, irreversible, diffusion-controlled cathodic waves corresponding to two electron transfer. The studies for the former were made in Britton-Robinson buffers of pH range 3.0 to 10.0, while for the latter the studies were carried out in dimethylformamide. The value of E1/2 shifts with increasing concentration of pyrazoles reveals irreversible reduction. Effect of electron donating substituents on E1/2 for both the series of compounds is reported. It was observed that the same group viz.−OCH3 and −OC2H5 shifts E1/2 towards more, positive value at the ortho position, while E1/2 is shifted towards more negative value at the para position.

Polarographic reduction of solochrome mordant dyes

Summary In order to understand their redox behaviour, polarographic reduction of solochrome yellow 2GS, solochrome red ERS, solochrome black PVS and solochrome black WDFA at the DME was studied. All these dyes were found to give diffusion controlled irreversible waves. The kinetic parameters of these waves have been determined and a new empirical relationship between E1/2 and pH, viz. E1/2=0.063−0.031 pH±0.003 has been reported. A detailed mechanism indicating the effect of substituents on the E1/2 of these dyes has also been suggested.

Effect of nonionic surfactants on the polarographic maximum and electrocapillary curves: A comparative study

The polarographic and electrocapillary curve methods have been used to determine the maximum suppression point (MSP), polarographic micelle point (PMP) and critical micelle concentration (cmc) of some polyoxyethylated nonionic surfactants, viz., Tween 20, Tween 40 and Tween 80. The cmc values thus obtained have been compared with the values obtained by surface tension, iodine solubilization, spectral dye and radiometric methods.

Determination of critical micelle concentration of non-ionic surfactants by electrocapillary curves

A method is described for the determination of the critical micelle concentration of non-ionic surfactants by measurement of their effect on the electrocapillary curves for a dropping mercury electrode. The method was compared with the iodine-solubilization, surface tension, and polarographic maximum suppression methods.

Polarographic studies on the interaction of copper with transfusion gelatin

Abstract The influence of the protein concentration, metal ion concentration and pH on the i d /( i d ) 0 values was studied by carrying out polarographic measurements in mixtures of cupric sulphate and transfusion gelatin. It was found that a decrease in the value took place with increase in protein concentration and pH, while the same behaviour was observed with decreasing concentration of Cu 2+ . The latter effect has been attributed to the binding of Cu 2+ with transfusion gelatin. Evaluation of log K showed that the copper is more strongly bound to the amino than to the carboxyl group.

Electrometric determination of critical micelle concentration of soap solutions

Abstract The variation of detergent anion activity with, concentration in solutions of potassium laurate, myristate, palmitate and stearate has been studied using the cobalt, cobalt soap electrode. The detergent anion activity increases at first, reaches a maximum at the c.m.c. and thereafter remains almost constant. The constant value of the activity above the c.m.c. shows that the excess of soap added goes into solution in the form of micelles. The c.m.c. values of potassium laurate, myristate, palmitate and stearate are 2.512 × 10−2 M, 6.918 × 10−3M ,3.162 × 10−3 M and 8.71 × 10−4M, respectively. In the presence of urea, the rnicellization of potassium laurate and myristate takes place at higher concentrations.