Safeer Ahmed

Synthesis, biological and electrochemical evaluation of novel nitroaromatics as potential anticancerous drugs

Nitroaromatics i.e. 1-nitro-4-phenoxybenzene (1), 4-(4-nitrophenyloxy) biphenyl (2), 1-(4-nitrophenoxy) naphthalene (3) and 2-(4-nitrophenoxy) naphthalene (4) were synthesized by Williamson etherification and characterized by elemental analysis, FTIR, NMR ((1)H, (13)C), UV-visible spectroscopy, mass spectrometry and single crystal X-ray diffraction analysis. Their brine shrimp cytotoxicity resulted in LD50 values <1 μg/mL indicating significant antitumor activity with IC50 values ranging from 29.0 to 8.4 μg/mL. They are highly active in protecting DNA against hydroxyl free radicals in a concentration dependent manner. Voltammetric studies showed one electron reversible reduction at a platinum electrode with diffusion coefficient (Do) values of the order ~10(-6)-10(-7) cm(2)s(-1). Strong interaction with the human blood DNA through intercalative mode was contemplated through electrochemical and UV-visible spectroscopic studies which are in agreement with the conclusions drawn from biological analysis, unravelling the potential anticancerous nature of the synthesized compounds.

Hydrogen Bonding Association in the Electroreduced Intermediates of Benzoquinones and Naphthoquinones

Keeping in view the importance of chemical and biological functions of quinone based couples; two different series of quinones, namely benzoquinones and naphthoquinones, are investigated electrochemically. Five compounds of each series are studied systematically in dichloromethane, acetonitrile, and propylene carbonate and from there the half-wave potentials of first and second reductions are obtained through cyclicoltammetry measurements. Four different alcohols are used with increasing concentrations as hydrogen bond donors on the basis of their increasing acidity. The hydrogen-bonding power is analyzed from the positive shifts in both the waves with increasing concentrations of alcohols. The quantitative comparison is made while calculating the thermodynamic association constants and number of alcohol molecules bonded to both anion and dianion of quinones. The qualitative behavior and quantitative data both indicate the quinone-alcohol interaction as hydrogen bonding and the strength of hydrogen bond is dependant upon the nature of species involved in this couple. From the cyclic voltammetric data the relative effects of hydroxylic additives and different substituted quinones on equilibrium constant are also observed. Solvent effect is rationalized in favor of hydrogen bonding in terms of solvent polarity parameters.

Electrooxidation of chloro, nitro, and amino substituted phenols in aqueous medium and their heterogeneous kinetics

The present study deals with the electrochemical investigation of seven different phenols through cyclic voltammetry (CV). Phenols can be partly eliminated from aqueous solutions by electrochemically initiated polymerization. Thus, the basic CV behavior was studied under the optimized conditions such as; pH of the medium, concentration of the analyte, the supporting electrolyte, potential window, and scan rate. The CV curves of all of the phenols showed that the electro-polymerization phenomenon on the electrode surface causes surface fouling for further electrooxidation of these compounds. The influence of substituents in the ring was especially noted in terms of their tendency to foul the electrode surface. The formation of new intermediates during the electrooxidation was observed whose nature was found to be highly dependent on the type and position of the substituent. As far as the influence of pH is concerned, phenols in basic medium were electrooxidized earlier but with low current. Difference in CV response because of the substituent attached under varied pH was also noted. From the diffusion coefficient (D) and heterogeneous rate constant (ksh) mixed nature of electron transfer process was proposed.

Electrical and thermoelectric attributes of Ba2Co2Fe12−2x(Ti–Mn)xO22 and their catalytic activity for complete N2O decomposition

A series of Ti–Mn co-doped Ba2Co2Fe12−2x(Ti–Mn)xO22 (x = 0.2–1.0) Y type hexaferrites has been synthesized by sol–gel method. Single phase hexagonal crystal structure was confirmed by X-ray diffraction analysis and Rietveld refinement with a crystallite size of 30–54 nm of the particles. Ti–Mn doping was uniform in the grains and there was no effect on the microstructure. Alternating current conductivity and dielectric properties were studied over a range of frequencies (20 Hz–3 MHz) for all the compositions. The resistivity increased with the dopant content while the dielectric constant decreased due to valence alteration of Fe3+ ions from the octahedral site by the dopants. Thermoelectric studies along with direct current resistivity results established the electron hopping conduction mechanism in the doped ferrites. The doped hexaferrites were used for the first time as the catalysts for complete N2O decomposition at a low temperature of 873 K. The electronic properties along with surface vacancies were found to be responsible for their efficient catalytic activity. Stability of the prepared material for several hours at the reaction temperature added to its catalytic application.

Mechanistic study of quinone-polyalcohol interaction through cyclic voltammetry

The electrochemistry of some quinones has been focused to determine the mode of interaction in presence of polyalcohols. Three compounds of each family (benzoquinones, naphthoquinones and anthraquinones) were investigated through cyclic voltammetry in the presence of ethylene glycol (a diol)) and glycerol (a triol) in dichloromethane and acetonitrile at 25°C. The observed positive shift in both the waves of the quinone with successive addition of alcohol was attributed to hydrogen bonding in the quinone-alcohol couple. “Two electron one step” electron transfer mechanism was proposed for the increase in the first wave height at the expense of second. The depletion of the first anodic wave at higher concentration of polyalcohol was rationalized in terms of protonation-deprotonation mechanism. A prior peak observed in the presence of glycerol was ascribed to the hydrogen bonding of the alcohol with neutral quinone. The difference in basicity strength within a family as well as among the three quinone families was also addressed in view of the interaction effectiveness.

Radical scavenging propensity of Cu(2+), Fe(3+) complexes of flavonoids and in-vivo radical scavenging by Fe(3+)-primuletin.

Cu2+ and Fe3+ complexes of three flavonoids (morin or mo, quercetin or quer and primuletin or prim) were synthesized with the objective of improving antioxidant capacities of flavonoids. The radical scavenging activities of pure flavonoids and their metal complexes were assayed to monitor their tendencies towards sequestering of radicals at physiological conditions. The scavenger potencies of metal-flavonoid complexes were significantly higher than those of the parent flavonoids. Further, influence of the solvent polarity on the radical capturing by flavonoids and their metal complexes was in favor for the polar solvent. Fe3+-prim displayed its radical scavenging ability via up gradation of CAT and SOD activities in in-vivo antioxidant assays.

Study of Partitioning and Solubilization of Some New Chalcones Between Aqueous and Micellar Phases

The partitioning behavior of four newly synthesized chalcones between aqueous and micellar phases of ionic surfactants (SDS and CTAB) was investigated using ultraviolet-visible spectroscopy. The simple absorption spectra were recorded to study the interaction between these drugs and surfactants (in the concentration range below critical micelle concentration to above critical micelle concentration). The absorption data is also used to determine the number of additive molecules incorporated per micelle of the surfactant. The partition coefficient (Kx) of additives between bulk water phase and the micellar phase was determined in the range of 5.52 × 10+4 to 5.06 × 10+5 at 298 K by differential spectroscopic method. The corresponding standard free energy of partition ΔG°p obtained was in the range of −27.05 kJmol−1 to −32.54 kJmol−1. The relative solubility of additives between aqueous and micellar phases in different micellar concentrations was also estimated. The results showed that the chalcones are preferably soluble in cationic surfactant micelles.

To explore a new class of material (X-type hexaferrites) for N2O decomposition

Nitrous oxide serves as a green propellant for space applications; however, an active and stable catalyst is required for its decomposition. A new class of material (X-type hexaferrites) was tested for this reaction for the first time. The catalysts were prepared by a co-precipitation method and a pure single hexagonal phase was confirmed by XRD and SEM. The developed pure and doped catalysts were found to be catalytically active for nitrous oxide decomposition reaction and the activity increased with increasing dopant content. However, Cr–Mn co-doped materials showed higher catalytic activity than Mn-doped samples. The cationic substitution and surface defects (oxygen vacancies) were found to be responsible for the upsurge of activity. The desired stability of the developed catalyst added to its potential for applicability.

Catalytic decomposition of N2O on cobalt substituted barium hexaferrites

Abstract Catalytic decomposition of N 2 O was studied over Co substituted Mg-Y type hexaferrites (Ba 2 Mg 2- x Co x Fe 12 O 22 , x = 0.4–2.0). The materials were synthesized by a sol-gel method using citric acid as the chelator followed by calcination at 1223 K for 5 h. X-ray diffraction, thermogravimetric analysis/derivative thermogravimetric, scanning electron microscopy, and N 2 adsorption techniques were used to confirm the formation of hexaferrite. The Ba 2 Mg 2- x Co x Fe 12 O 22 catalysts displayed good activity for decomposition of high concentration N 2 O (30 vol%), and complete substitution of Mg for Co lowered the complete conversion temperature from 1123 K to 973 K. Increasing calcination temperature suppressed the catalytic activity by deteriorating surface area. Moreover, coupling microwave discharge significantly boosted the catalytic activity. Co substituted Mg-Y type hexaferrites are potentially active and thermally stable to be used as catalyst for high concentration N 2 O decomposition.

Formation of low density hydrous iron oxide via conformal transformation of MIL-53(Fe).

Hydrous iron oxide materials with a predefined shape, photo-electrochemical activity, low density (estimated to be 0.32 g cm(-3)), and high fractal porosity (BET ca. 117 m(2) g(-1)) are formed via internal hydrolytic transformation of the crystalline metal-organic framework MIL-53(Fe) in dilute aqueous hydroxide.