Zareen Akhter

Voltammetric and spectroscopic investigations of 4-nitrophenylferrocene interacting with DNA.

Cyclic voltammetry (CV) coupled with UV-vis and fluorescence spectroscopy were used to probe the interaction of potential anticancer drug, 4-nitrophenylferrocene (NFC) with DNA. The electrostatic interaction of the positively charged NFC with the anionic phosphate of DNA was evidenced by the findings like negative formal potential shift in CV, ionic strength effect, smaller bathochromic shift in UV-vis spectroscopy, incomplete quenching in the emission spectra and decrease in viscosity. The diffusion coefficients of the free and DNA bound forms of the drug were evaluated from Randles-Sevcik equation. The binding parameters like binding constant, ratio of binding constants (K(red)/K(ox)), binding site size and binding free energy were determined from voltammetric data. The binding constant was also determined from UV-vis and fluorescence spectroscopy with a value quite close to that obtained from CV.

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.

Synthesis, Characterization, and Pharmacological Evaluation of Selected Aromatic Amines

Aromatic amines 1-amino-4-phenoxybenzene (A-1A), 2-(4-aminophenoxy) naphthalene (A-2A), and 1-(4-aminophenoxy) naphthalene (A-3A) were synthesized by the reduction of corresponding nitroaromatics with hydrazine monohydrate and Pd/C 5% (w/w). The newly synthesized compounds were characterized by FTIR, 1H NMR, 13C NMR, UV-visible spectrophotometer, and mass spectrometry and their biological activities were investigated along with structurally similar 4-(4-aminophenyloxy) biphenyl (A-A). Results of brine shrimp cytotoxicity assay showed that almost all of the compounds had LD50 values <1 μg/mL. The compounds also showed significant antitumor activity with IC50 values ranging from 67.45 to 12.2 µgmL−1. The cytotoxicity and antitumor studies correlate the results which suggests the anticancerous nature of compounds. During the interaction study of these compounds with DNA, all of the compounds showed hyperchromic effect indicating strong interaction through binding with the grooves of DNA. Moreover, A-3A also showed decrease in confirming higher propensity for DNA groove binding. In DPPH free radical scavenging assay, all the compounds showed potential antioxidant capability. The compounds were highly active in protecting DNA against hydroxyl free radicals. DNA interaction and antioxidant results back up each other indicating that these compounds have potential to be used as cancer chemopreventive agents. Additionally, one compound (A-1A) showed significant antibacterial and antifungal activity as well.

A New Ferrocene‐Containing Polyamide Prepared from an Improved Synthesis of 1,1′‐Ferrocene Dicarbonyl Chloride and Ferrocene‐Based Diamine

Abstract 1,1′‐Ferrocene dicarbonyl chloride was prepared by an improved and efficient conversion method from 1,1′‐ferrocene dicarboxylic acid and reacted by esterification with p‐nitrophenol, followed by reduction, to form a ferrocene‐based diamine, 1,1′‐ferrocene bis (p‐amino phenylate). The diamine was characterized by elemental analysis, 1H NMR, and Fourier transform infrared (FTIR) spectroscopy and subsequently condensed with 1,1′‐ferrocene dicarbonyl chloride to form a novel main chain ferrocene‐containing polyamide, poly{imino ferrocene bis (p‐amino phenylate) ferrocenyl}. Its polymeric nature was confirmed by its physical properties, elemental analysis, FTIR spectroscopy, differential scanning calorimetry, and thermogravimetric studies.

Systematic formation of mixed-metal high-nuclearity clusters: the synthesis and characterisation of [Os6(CO)17(Au2dppm)] and [Os6(CO)17(Au2dppm){Ru(η5-C5H5)}2] (dppm=Ph2PCH2PPh2)

Abstract Reaction of the hexaosmium cluster [Os 6 (CO) 18 ] with 1.1 equivalents of Me 3 NO, in CH 2 Cl 2 , in the presence of one equivalent of [Au 2 dppm]Cl 2 (dppm=Ph 2 PCH 2 PPh 2 ), at room temperature, affords the new mixed-metal cluster [Os 6 (CO) 17 (Au 2 dppm)] ( 1 ), in high yield. Subsequent reduction of 1 with Na–Hg amalgam, and subsequent treatment with [Ru(η 5 -C 5 H 5 )(MeCN) 3 ][PF 6 ] ( 2 ) afforded two decanuclear clusters [Os 6 (CO) 17 (Au 2 dppm){Ru(η 5 -C 5 H 5 )} 2 ] ( 3 ) and [Os 6 (CO) 16 (Au 2 dppm){Ru(η 5 -C 5 H 5 )} 2 ] ( 4 ) in moderate yield. Cluster 3 loses CO under reflux in toluene to produce 4 . The new clusters have been fully characterised by IR, 1 H- and 31 P-NMR spectroscopies, and mass spectrometry. The molecular and crystal structures of 1 and 3 have been established by single-crystal X-ray analyses. In 1, the bicapped tetrahedral osmium core of [Os 6 (CO) 18 ] is retained and the two Au atoms of the Au 2 dppm group cap one Os 3 face in a μ 3 -η 2 bonding mode. In 3 the metal core consists of a capped square-based pyramidal arrangement of Os atoms that is capped over the square face by the Au 2 dppm group. One Ru atom caps another face of the Os 5 square-based pyramid, and the second Ru atom caps the Ru atom, two Os atoms and an Au atom to form a trigonal bipyramidal arrangement.

Addition of some gold electrophiles to an octa-osmium carbonyl cluster: Thermodynamic vs. kinetic control

Abstract The reaction of the dianionic cluster [PPN] 2 [Os 8 (CO) 22 ] {[PPN] + =[N(PPh 3 ) 2 ] + } with Au 2 Cl 2 L {L=chelating phosphines bis -(diphenylphosphino)methane (dppm), 1,2- bis -(diphenylphosphino)ethane (dppe) or 1,4- bis -(diphenylphosphino)butane (dppb)} in the presence of an excess of the halide acceptor TlPF 6 , affords the neutral digold-substituted clusters [Os 8 (CO) 22 (Au 2 L)] {(1) L = dppm; ( 2 ) L = dppe; ( 3 ) L = dppb} in almost quantitative yield. The 31 P{1H} NMR spectra of these compounds indicate that the gold atoms are in non-equivalent environments and therefore cannot have a metal geometry similar to that previously reported for the related cluster [Os 8 (CO) 22 (AuPPh 3 ) 2 ]1 (4). A reinvestigation of the reaction between [PPN] 2 [Os 8 (CO) 22 ] and monogold fragment ‘AuPPh 3 + ’ has shown that, in addition to ( 4 ), a second isomer of Os 8 (CO) 22 (AuPPh 3 ) 2 ] ( 5 ) is formed, which on the basis of the spectroscopic data is thought to have the same metal geometry as compounds ( 1-3 ). A single crystal X-ray diffraction study of the compound [Os 8 (CO) 22 (Au 2 dppb)] ( 3 ) has shown that the metal core consists of a bicapped octahedron of osmium atoms, with one of the gold atoms capping the osmium octahedron, and the other gold atom bridging an edge of the osmium core.

Metal core rearrangements in hetero-bimetallic nona-osmium carbonyl clusters; the crystal and molecular structures of [Os 9 (CO) 24 {Au(PCy 3 )} 2 ] and [Os 9 (CO) 23 (Au 2 DPPE)]

The reaction of the nona-osmium cluster dianion [(Ph 3 P) 2 N] 2 [Os 9 (CO) 24 ] with the electrophilic gold reagents and “Au 2 L 2+ ” (where R=Ph ( 2a , 3a ), Cy ( 2b , 3b ) and L=bis-(diphenylphosphino)methane (DPPM) ( 1a ) or 1,2-bis-(diphenyl)ethane (DPPE) ( 1b )) has been studied. The monogold fragment reacts to give both the mono- and di-substituted products [(Ph 3 P) 2 N][Os 9 (CO) 24 {Au(PR 3 )}] and [Os 9 (CO) 24 {Au(PR 3 )} 2 ]. The structure of the latter cluster (R=Cy ( 2b )) has been determined by a single crystal X-ray diffraction analysis and a major rearrangement of the metal core geometry was found to have occurred on coordination of the gold fragments. In contrast, reaction with the digold reagent “Au 2 L 2+ ” results in the isolation of only one product of formulation [Os 9 (CO) 23 (Au 2 L)], where coordination of the heteroatom moiety has been accompanied with the loss of a carbonyl ligand. From a single crystal X-ray diffraction analysis (L=DPPE ( 1b )) this compound was shown to have retained its original cluster geometry, with the gold atoms coordinated in close proximity to each other.

Conducting poly(azomethine)esters: synthesis, characterization and insight into the electronic properties using DFT calculations

A poly(azomethine)ester was synthesized via solution phase polycondensation of isophthaloyl chloride and preformed 4-((2-(4-hydroxibenzylideneamino)ethylimino)methyl)phenol (SB). Various aliphatic and aromatic moieties were incorporated in the parent chain to process them and for examining their effect on the conducting properties. To provide an insight into the electronic properties, DFT calculations at the 6-31G/B3LYP level were carried out. Emphasis was placed on exploring the Frontier electron density, energy gaps and electrostatic potential maps to predict their conducting behaviour and electrophilic/nucleophilic reactivity. Our results based on experimental data and theoretical studies showed that in spite of some discrepancies, the electronic properties can be approximated theoretically to design a material having the desired properties for organic electronic devices. The material was characterized by FTIR, 1H NMR spectroscopic studies and elemental analysis.

Solid-state 13C, 15N and 29Si NMR characterization of block copolymers with CO2 capture properties

Natural abundance solid‐state multinuclear (13C, 15N and 29Si) cross‐polarization magic‐angle‐spinning NMR was used to study structures of three block copolymers based on polyamide and dimethylsiloxane and two polyamides, one of which including ferrocene in its structure. Assignment of most of the resonance lines in 13C, 15N and 29Si cross‐polarization magic‐angle‐spinning NMR spectra were suggested. A comparative analysis of 13C isotropic chemical shifts of polyamides with and without ferrocene has revealed a systematic shift towards higher δ ‐values (de‐shielding) explained as the incorporation of paramagnetic ferrocene into the polyamide backbone. In addition, the 13C NMR resonance lines for ferrocene‐based polyamide were significantly broadened, because of paramagnetic effects from ferrocene incorporated in the structure of this polyamide polymer. Single resonance lines with chemical shifts ranging from 88.1 to 91.5 ppm were observed for 15N sites in all of studied polyamide samples. 29Si chemical shifts were found to be around −22.4 ppm in polydimethylsiloxane samples that falls in the range of chemical shifts for alkylsiloxane compounds. The CO2 capture performance of polyamide‐dimethylsiloxane‐based block copolymers was measured as a function of temperature and pressure. The data revealed that these polymeric materials have potential to uptake CO2 (up to 9.6 cm3 g−1) at ambient pressures and in the temperature interval 30–40 °C. Copyright

N-(3-Nitro­benzyl­idene)aniline

In the title compound, C13H10N2O2, a Schiff base derivative, the dihedral angle between the two aromatic rings is 31.58 (3)°. The C=N double bond is essentially coplanar with the nitrophenyl ring. The torsion angle of the imine double bond is 175.97 (13)°, indicating that the C=N double bond is in a trans configuration. The crystal structure is stabilized by C—H⋯O contacts and π–π interactions (centroid–centroid distances of 3.807 and 3.808Å).