Hammed H. A. M. Hassan

Synthesis and characterization of thermally stable aromatic polyamides and poly (1,3,4-oxadiazole-amide)s nanoparticles containing pendant substituted bezamides

BackgroundThe introduction of pendent bulky groups along the polymer backbone results in a less ordered polymer matrix and increases the solubility characteristics without affecting thermal properties. The inclusion of chromogenic chemical moieties in the chains can give rise to the luminescent converter material which permits the preparation of materials with potential applications. Aromatic polymers containing heterocyclic rings in the main chain are known for their high thermal resistance, good hydrolytic stability, low dielectric and tough mechanical properties. There is currently much research directed towards the discovery of new blue light-emitting polymers, with characteristics of high efficiency and high reliability. Herein, we describe the preparation of aromatic polyamides and poly (1,3,4-oxadiazole-amide)s nanoparticles with pendant structures comprised of m- and p-acetoxybenzamide groups, where the acetoxybenzamide groups act as signaling units due to their fluorescent and chromogenic characteristics.ResultsAromatic polyamides and poly(1,3,4-oxadiazole-amide)s nanoparticles with pendant structures comprised of m- and p-acetoxybenzamide groups were successfully prepared and characterized using different analytical methods. Most polyamides were obtained as well-separated spherical nanoparticles while aramide containing pyridine produced aggregated particles attributed to the molecular self assembly via H-bond directed organization of molecular precursors. The thermal behavior of all polymers exhibited two major thermal decompositions due to the subsequent breakage of the acetoxy group in the lateral chain and cleavage of the main amide bonds. Photoluminescence studies revealed that the blue emissions for the polyamide derived from benzidine were blue-shifted (shifted to a lower wavelength) compared to that of polyamides containing flexible linkages.ConclusionsWe report the synthesis of aromatic polyamides and poly(1,3,4-oxadiazole-amide)s nanoparticles with pendant structures comprised of m- and p-acetoxybenzamide groups. The thermal behavior of all polymers exhibited two major decompositions due to breakage of the acetoxy group in the lateral chain and cleavage of the main amide bonds. Structure- photoluminescence correlation demonstrated an interesting connection between structural modification and optical properties. The blue emissions for the polyamide derived from benzidine, attributed to the highly conjugation system, was blue shifted with the introduction of flexible linkages. The prepared polymers dissolved in warm polar aprotic solvents. Further investigations to obtain films with reasonably good mechanical properties for different applications are in progress.

Antimicrobial and antitumor activity of platinum and palladium complexes of novel spherical aramides nanoparticles containing flexibilizing linkages: structure-property relationship.

Square planar Pd (II) and octahedral Pt (IV) complexes with novel spherical aramides nanoparticles containing flexible linkages ligands have been synthesized and characterized using analytical and spectral techniques. The synthesized complexes have been tested for their antimicrobial activity using Kirby-Bauer disc diffusion method. The antitumor activity has been performed using liver carcinoma (HEPG2), breast carcinoma (MCF7) and colon carcinoma (HCT 116) cell lines. Palladium complexes of polyamides containing sulfones showed the highest potency as antibacterial and antifungal agents. Platinum complexes containing sulfone and ether flexible linkages and chloro groups exhibited high potency as antitumor and antimicrobial agents. The uniform sizes of these nanomaterials could find biological uses such as immune assay and other medical purposes.

Synthesis of Novel Semiconducting Aromatic Polyesteramids Containing Pyridine: Characterization of Nanometer-Sized Rod-Like Analogues and their Copper (II) Complexes

In this paper, new thermally stable isomeric unsubstituted polyesteramides have been successfully prepared by condensation of aromatic acids chlorides namely; isophthaloyl, pyridine-3,5-dicarbonyl and pyridine-2,6-pyridine-dicarbonyl dichlorides with the aminophenol isomers in NMP. Conducting the reaction in NMP/H2O (90/10 v/v) followed by centrifugal separation furnished the desired polymers as rod-like nanoparticles. The morphology of obtained nanoparticles were studied by SEM. Mixing NMP with H2O was essential for controlling the particles morphology and as a reaction accelerator. Pyridine-containing polymers exhibit semi-conducting nature as their conductivities increase with increasing temperature, while no variation of the conductivity with the temperature was observed for their corresponding phenylene analogues. Introduction of the nitro group into the polymer backbone led to a red shift in the absorption and the obtained polymers have a bright yellow color, which is unusual with this polymer group. Copper (II) ions were complexed the polyesteramides-containing nitro group in a (1:1) ratio. Complexes of pyridine-containing polymers exhibit semiconducting nature changed to metallic characters on heating and their conductivities increased tens of magnitudes than their corresponding ligands. These new types of polymeric materials and their nano-sized rods may have numerous applications in nanotechnology and their properties can be tuned for specific applications such as conducting adhesives and coating materials.

Synthesis of carbohydrate-containing polyamides and study of their properties☆

Abstract Carbohydrate-containing polyamides were prepared using low-temperature solution polycondensation of 2,3,4,5-tetra-O-acetylgalactaroyl dichloride (3) with various aromatic and aliphatic diamines viz. p- phenylenediamine ( 4 ) ; m-phenylenediamine; benzidine; 4,4′-diaminodiphenylmethane; 1,5-diaminoanthraquinone; 2,6-diaminoanthraquinone; 4,4′-diaminodicyclohexylmethane; hexamethylenediamine; and ethylenediamine (12). The four O-acetyl groups in 3 protect the hydroxyl functions and give good solubility as a result of increasing lipophilicity. The optimum conditions for the best yield and viscosity of the polyamide were determined by study of the factors affecting the polycondensation. These conditions for reaction of 3 with 4 were reached with reactant concentrations of 0.5 mol/l at −10°. On the other hand, the optimum conditions for reaction of 3 with 12 involved concentrations of 1.0 mol/l at 0°. Polyamides containing the unacetylated carbohydrate chains were obtained by de-O-acetylation of the synthesized acetylated carbohydrate-containing polyamides. Structures of the acetylated and de-O-acetylated carbohydrate-containing polyamides were confirmed by elemental analysis, i.r. and 1H-NMR spectroscopy. Their thermal degradations were studied by differential thermal analysis and thermogravimetric analysis.

Antioxidant Activity of New Aramide Nanoparticles Containing Redox-Active N-phthaloyl Valine Moieties in the Hepatic Cytochrome P450 System in Male Rats

We report the synthesis of aramide nanoparticles containing a chiral N-phthaloyl valine moiety and their antioxidant activities on hepatic contents of cytochrome P450, amidopyrene N-demethylase, aniline-4-hyroxylase and induced the hepatic content of cytochrome b5 and nicotinamide adenine dinucleotide phosphate (NADPH) cytochrome C-reductase. Polymers were obtained as well-separated spherical nanoparticles while highly aggregated particles via H-bonding organization of the aramide-containing pyridine led to a thin layer formation. The effects of the nanoparticles and CCl4 on enzyme activities and thiobarbituric acid reactive substances (TBARS) levels of male rat liver were studied. Pretreatments of rats with the polyamides prior to the administration of CCl4 decreased the hepatic content of the tested enzymes. Doses reduced the toxic effects exerted by (•CCl3) upon the liver through inhibition of the cytochrome P450 system. Inhibition of such metabolizing enzymes could reduce the carcinogenic effects of chemical carcinogens.

Synthesis and Properties of Narrow-sized Spherical Aramides Nanoparticles Containing Pyridine and their Copper (II) Complexes

We report the preparation of narrow-sized well-separated spherical aramides nanoparticles containing pyridine using the precipitation polymerization method. The average diameter of the particles ranges from 50–98 nm. Particles of pyridine containing polymers exhibited large diameter compared to their phenylene counterpart. Symmetric meta-polymers showed relatively higher ηinh and thermal stability and thus higher degree of polymerization than their nonsymmetrical counterparts. Incorporation of Copper (II) ions into these polymers furnished copper-polymer complexes in a (1:2) ratio and the reported structures are proposed on the basis of their IR, UV, ESR and elemental analysis data. The ERS spectra of the complexes exhibited typical axial spectra with g// and g⊥ features and the data indicated that the copper site has a dx2-y2 ground state, characteristic of square planar or elongated octahedral stereochemistry. The incorporation of copper into aramides backbones significantly improved their optical and thermal properties. The dc electrical conductivity of polymeric copper complexes revealed different behaviors and it is obvious that the prepared pyridine-containing polymers exhibited higher σ values compared to their phenylene analogues. These types of nano-sized aramides and their copper complexes may find some applications as new semiconducting nanoparticles.

Structure–property relationship studies of copper(I) complexes of nanosized hypodentate ligands and evaluation of their antitumor and antimicrobial activities

We report the preparation of four nanosized isomers of N-benzoyl-N′-(hydroxyphenyl) thioureas by nanoprecipitation. Direct reactions with CuCl2·2H2O gave the corresponding complexes in good yields. The structures of the ligands and their copper complexes were characterized using different analytical and spectroscopic measurements. In all complexes, the data revealed non-electrolytic mononuclear three-coordinate copper(I) complexes, where the ligand is hypodentate to copper ion via thioamide sulfur. Thermal studies revealed high thermal stability of the complexes compared to their parent ligands and the mechanism of decomposition and the thermodynamic parameters were evaluated. The ligands and their complexes were screened against different pathogenic microorganisms, and subjected to in vitro antioxidant and cytotoxic activities against three human cell lines. Compared to other isomers, N-benzoyl-N′-(o-hydroxyphenyl) thiourea exhibited significant antimicrobial activity and had higher activity than the standard fungicides and bacteriocides. All copper complexes showed inhibitory potencies, however [Cu(H2L2)2Cl] exhibited remarkable inhibitory activities against the examined cancer cell lines as evident by the range of IC50 values (4.0–7.4 μg/mL) and the percentage of cell viability. The results obtained can find medical applications as new therapeutic nanoparticle agents.

Synthesis and GC-Eims Analyses of Optically Pure 3-Hydroxy-2-Azetidinones Having N-Sulfonamide Drugs Side Chain

Abstract A series of new N-sulfonamides of substituted 3-hydroxy-2-azetidinones were prepared by the [2+2] cycloaddition of aldoximes, formed from the condensation of D-(R)-glyceraldehyde acetonide and the potent p-aminophenyl-N-substituted sulfonamides, with benzyloxyacetyl chloride followed by removal of the protecting groups. Obtaining both diastereoisomeric forms of β-lactams by resorting to kinetic resolution starting from racemic imino analogue is also described. The GC-EIMS, spectroscopic and analytical analyses for some of these derivatives are reported.

Chemistry and Biology of Heparin Mimetics that Bind to Fibroblast Growth Factors

We aim from this review to stimulate further research in this area by providing a description of the different types of inhibitors containing heparin mimetic molecules that have recently been reported and data on their biological activity. Molecules that mimic heparin and bind to heparin-binding growth factors are important building blocks for synthetic biomaterials. Different types of synthetic mimics of the biological properties of heparin have been prepared inclu-ding high molecular weight compounds or small molecule mimics. Peptide-based mimics of heparin functionality are limited and because of their low degree of sulfation, they are natural targets as heparin mimics. Aromatic sulfonamide derivatives exhibit a range of bioactivities and a novel angiogenesis inhibitor (E 7820) is used as a TF model for screening assay. The anticoagulant activity of the known heparin pentasaccharide sequence prompted synthetic efforts aimed at the procurement of this structure as well as a host of related sequences. Chemical modification of the natural or synthetic heparin increased factor activation of AT III Xa affinity. A variety of non-peptide non-saccharides inhibitors as anti-angiogenesis therapies directed against the VEGFR kinase are a promising and well-validated therapeutic approach under active evaluation of their safety and efficacy in multiple clinical trials. These low molecular weight modulators could be useful tools for biologists and may have potential as drugs or as leads for drug development.

Synthesis and Thermal Properties of Novel Polyamides Containing α-Amino Acid Moieties: Structure-Property Relationship

We report the preparation of a library of new types of polyamides-containing amino acids based on eight new symmetric meta-oriented protected diamines derived from coupling four Fmoc-amino acids namely Gly, Ala, Val, Leu, with m-phenylene diamine or 2,6-diaminopyridine using three different coupling procedures. The thermal properties of the polymers were evaluated by different techniques. Results revealed that incorporation of pyridine onto the polymeric backbone of all series decrease the thermal stability. Structure-thermal property correlation based on changing the dicarboxylic acid monomer or the diamine monomer demonstrated an interesting connection between a single change and thermal properties. The thermodynamic parameters of decomposition processes were evaluated graphically by employing the Coats-Redfern method. The newly prepared polymers may possess biodegradability and thus, may find some applications as novel biomaterials.