Muhammad Javed Iqbal

Partial molar volume of mefenamic acid in alcohol at temperatures between T=293.15 and T=313.15 K

Apparent molar volume (VF), partial molar volume (V), solute-solute interaction parameter (Sv), partial molar expansivity (E02) and isobaric thermal expansion coefficient (a2) of mefenamic acid in six different organic solvents namely, methanol, ethanol, 1-propanol, 2-propanol, 1-butanol, and 2-butanol, have been calculated from the measured solution densities over a temperature range of T=293.15 and T=313.15±0.1K. The solution densities were measured by an automated vibrating tube densitymeter (Anton Paar DMA-48). The molality range investigated was between 6×10-3 and 3.25 ×10-2 mol kg -1. The effect of temperature on apparent molar volume and partial molar volume was also determined. Decrease in solute-solvent interactions with an increase in temperature has been noted. Partial molar volume of mefenamic acid changes with the change in solvent polarity.

Physical, electrical and magnetic properties of nano-sized Co-Cr substituted magnesium ferrites

Co-Cr substituted magnesium ferrite nanomaterials (Mg1−xCoxCrxFe2−xO4 with x = 0.0−0.5) have been prepared by the polyethylene glycol assisted micro emulsion method. X-ray diffraction analysis confirms the single-phase cubic close-packed lattice formation of synthesized materials. Hysteresis loops are measured up to field of 4 MA/m and high field region of these loops are modeled using the Law of Approach to saturation to calculate the magnetocrystalline anisotropy constant. The saturation magnetization of the samples increases initially from 148 kA/m for x = 0.0 to 299 kA/m (x = 0.3) and then decreases to 187 kA/m (x = 0.5). Curie temperature for this series is found to be in the range of 618-766 K. Room temperature resistivity increases gradually from 7.5 × 108 Ω cm (x = 0.0) to 3.47 × 109 Ω cm (x = 0.5). Additionally, dielectric measurements are carried out at room temperature in a frequency range of 100 Hz to 3 MHz. With improvement in the values of the above-mentioned properties, the synthesized materials could be suitable for potential application in some magnetic and microwave devices.

Synthesis, crystal structure description, electrochemical and DNA binding studies of ‘paddlewheel’ copper(II) carboxylate

Dimeric paddlewheel copper(II) complex, pyCu(phenylacetate)4Cupy, where py = pyridine, has been prepared and the crystal structure determined. Single crystal X-ray diffraction (XRD) revealed three crystallographically independent molecules in the unit cell. The geometry around each Cu(II) is square pyramidal with monodentate pyridine at the apical and bidentate carboxylates in the equatorial positions. The supramolecular structure of the complex arises primarily as a result of C–H⋯O along with some contribution of C–H⋯C interactions, resulting in the preferential alignment of the molecules along the c-axis. The purity of the crystalline complex has been confirmed through powder XRD study. Electrochemical solution study of the complex in aqueous DMSO (1 : 4) showed two redox couples corresponding to Cu(III)/Cu(II) and Cu(II)/Cu(I) irreversible electron transfer. The values of various voltammetric variables, such as diffusion coefficient (Do), heterogeneous rate constant (k°), formal potential (E°), and charge transfer coefficient (α), have been calculated before and after DNA addition. DNA binding of the complex has been explored through cyclic voltammetry, UV–visible spectrophotometry, and viscosity measurement which have exhibited a mixed electrostatic and intercalative mode of interaction. Cyclic voltammetry indicated self-induced redox activation and potential anticancer ability of the complex, supported by UV–visible spectrophotometry as well as viscometry. Graphical Abstract

Thermal analysis of renal stones

The chemical composition of 200 renal stones, collected from Taxila, Rawalpindi and Islamabad regions in Pakistan, was determined by thermogravimetric (TG) and differential thermal analysis (DTA) techniques. The thermal curves show weight losses at various temperatures indicating dehydration and decomposition phenomena of renal stones. Results were compared with qualitative data obtained by IR analysis which confirmed the chemical composition of various stones in the solid state. The thermal curves helped in the differentiation of various kinds of water held by stones and their chemical composition was obtained by weight loss during pyrolysis. It was found that 26.5% of the stones were pure whewellite, 3% weddellite, 13% uric acid anhydrous, 7.5% struvite, 2.5% ammonium acid urate, 0.5% cystine and 47% stones had mixed composition. In the mixed state the most frequent combinations were those of calcium oxalate with uric acid (14.5%) and with phosphates (27.5%).ZusammenfassungMittels TG und DTA wurde die chemische Zusammensetzung von 200 Nierensteinen untersucht, die in den Gebieten Taxila, Rawalpindi und Islamabad in Indien gesammelt wurden. Die Thermogramme zeigen Masseverluste bei verschiedenen Temperaturen, die auf Dehydratation und Zersetzung der Nierensteine hinweisen. Die Ergebnisse wurden mit den qualitativen Resultaten aus der IR-Analyse verglichen, welche die chemische Zusammensetzung der verschiedenen Steine im festen Zustand bekräftigte. Die Thermogramme halfen bei der Unterscheidung von verschieden gebundenem Wasser, ihre chemische Zusammensetzung wurde durch Gewichtsverlust bei der Pyrolyse bestimmt. Man fand, daß 26.5 % der Steine aus reinem Whewellit bestanden, 3 % aus Weddellit, 13 % aus anhydrierter Harnsäure, 7.5 % aus Struvit, 2.5 % aus Ammmoniumhydrogenurat, 0.5 % aus Cystin und 47 % der Steine hatten eine gemischte Zusammensetzung. Die häufigsten Kombinationen der Mischzusammensetzungen waren Calciumoxalat mit Harnsäure (14.5 %) und mit Phosphaten (27.5 %).

Adsorption Studies of Ni(II) from Aqueous Solution onto Bentonite

Abstract A flame atomic absorption method was employed to study the removal of Ni(II) from aqueous solution onto bentonite surface, using the batch equilibrium method. Maximum removal (80%) was achieved from a solution of pH 3.2. Effect of various parameters like concentration, shaking time and temperature were examined to achieve the optimized conditions of maximum recovery of Ni(II) from solution by adsorption method. The effect of various anions and cations on the recovery of Ni(II) was also investigated. The data were investigated in terms of calculating thermodynamic quantities and were found to fit well to Freundlich equation.

Effect of annealing temperature and substitution of Zr-Cu on magnetic properties of strontium hexaferrite nanoparticles

ZnTe and ZnTe:Cr films were prepared onto glass substrates using the thermal evaporation method. Structural properties of the prepared samples were analyzed using X-ray diffractometry, and the presence of a ZnCrTe phase was identified along with poor crystallinity. Composition analysis was done using XPS and the Cr content in the film was found to be 0.05 atomic percent. Transmittance spectra were recorded using UV-Vis spectrophotometry. The valence state of Cr in ZnTe:Cr film is determined to be +2 using electron spin resonance (ESR) spectroscopy. Magnetic moment data as a function of magnetic field were recorded using a Superconducting Quantum Interference Device (SQUID) magnetometer at temperatures of 5, 77 and 300 K. The results showed minority ferromagnetic behavior even at room temperature. Magnetic domains were observed using Magnetic Force Microscopy and the average domain size is 3.7 nm.

One-pot synthesis, structural elucidation, DNA binding and alkaline phosphatase inhibition studies of zinc(II) complexes with 4-nitrocinnamic acid and ethylenediamine

We report one-pot synthesis of zinc(II) complexes with 4-nitrocinnamic acid (HL), [ZnL2(H2O)2] (1), [ZnL2(DMSO)2] (2) and [Zn(en)2(H2O)2]L2(H2O)2 (3), where DMSO = dimethylsulfoxide and en = ethylenediamine. The complexes were prepared by reacting sodium 4-nitrocinnamate with zinc acetate in aqueous medium and characterized by FT-IR, NMR and single crystal X-ray diffraction. The results have shown distorted octahedral geometry for 1 and 3 while tetrahedral for 2 where the carboxylate coordinated bidentate and monodentate in 1 and 2 is uncoordinated in 3, replaced completely by ethylenediamine. The complexes were also screened for their DNA interaction and alkaline phosphatase (ALP) inhibition using cyclic voltammetry, viscometry and UV–visible spectroscopy. All these techniques indicated strong electrostatic binding of the complexes with DNA. The diffusion coefficients of the complexes decreased on DNA addition indicating binding of the complexes with DNA. The binding constants were also calculated through CV and UV spectra. The complexes were screened for ALP inhibition activity as well, where 80% activity was found for 1. Graphical Abstract The synthesized compounds interact with DNA via intercalative mode of interaction.

Synthesis, characterization, crystal structures, enzyme inhibition, DNA binding, and electrochemical studies of zinc(II) complexes

Five zinc(II) complexes, [Zn(L1)2] (1), [Zn(L1)2(phen)H2O]·H2O (2), [Zn(L1)2(bipy)] (3), [Zn(L2)2] (4), and [Zn(L2)2(phen)] (5) (where L1 = 4-nitrophenylacetate, L2 = phenylacetate, phen = 1,10-phenanthroline and bipy = 2,2′-bipyridine), have been synthesized and characterized by elemental analysis, FT-IR, and multinuclear NMR. Complexes 2, 3, and 4 have been confirmed by single-crystal X-ray diffraction. In 2 and 3, zinc is bonded monodentate to two carboxylates exhibiting distorted trigonal bipyramidal and tetrahedral geometries, respectively, whereas in 4, the carboxylates are bridging bidentate in distorted tetrahedral geometry. The complexes have been screened for electro- and biological activities, including DNA interaction and enzyme inhibition studies. The effect of concentration of 1–5 on the activity of enzyme, alkaline phosphatase, showed that an increase in concentration of complex decreased the activity of the enzyme. Electrochemical behavior of HL1, 2, and 3 was investigated by cyclic voltammetry and it was observed that ligand-centered electro-activity exhibits a proportionate change on complexation. The UV–visible spectroscopic and viscometric data indicate electrostatic and groove binding of the complexes with DNA. The binding constant and Gibb’s free energy values indicate the feasibility of the complex–DNA interaction and show potent biological activity of the complexes. Graphical Abstract

Biosorption of lead(II) by free and immobilised fungal biomass of Phanerochaete chrysosporium: a comparative study

An efficient metal biosorbent was developed by immobilising fungal biomass within matrix of loofa sponge (FBILS). At biosorption equilibrium FBILS removed 137 mg Pb(II) g-1, which was 24.3% greater than 110 mg Pb(II) g−1 free fungal biomass. The equilibrium biosorption data fitted well the Langmuir model. The experimental data, when applied to the pseudo-first and second-order kinetic models, followed the second-order with r² 0.996. Metal desorption from the Pb(II)-laden FBILS with 50 mM HCl was 99%, and the regenerated FBILS was repeatedly used in seven biosorption-desorption cycles without significant loss in biosorption capacity. The study indicated high potential of FBILS for effective removal of Pb(II) from industrial wastewater.

Oxovanadium complexes with multidentate ligands

Vanadium has ability to coordinate with multidentate ligands in different geometries to produce variety of complexes. Usually the reactions are carried out by refluxing the methanolic solution of oxovanadium salt (VOSO4) with the ligands. Vanadyl sulphate can easily exchange its sulphate group with organic ligands. Sometimes solvent molecules are also attached with the complexes. Vanadyl oxygen usually occupies the axial position. The syntheses and geometries, and selective crystal structures of these complexes are discussed.