Investigation of thermal, antibacterial and heavy metal ion removal behavior of polyamide/polyimide iron oxide nanocomposites

In this study, a newly-designed diamine (DA) containing pyridine and carbazole groups was synthesized and the relevant polyamides (PAs) and polyimides (PIs) were prepared by polymerization reaction between the DA monomer and terephthalic acid, adipic acid, and pyromellitic dianhydride. In addition, polymer nanocomposites were prepared through a combination of the synthesized polymers with modified magnetite iron oxide nanoparticles. The synthesized compounds were fully characterized by hydrogen nuclear magnetic resonance (1HNMR), fourier-transform infrared (FTIR), field emitting scanning electron microscopy (FESEM), energy dispersive X-Ray (EDX), Transmission electron microscopy (TEM), Differential scanning calorimetry (DSC) and Thermogravimetric analysis (TGA) analyses. All of the synthesized properties of compounds such as thermal stability, viscosity, elimination capability of heavy metals ions adsorption, and antibacterial activity were investigated. Polyamides and PI showed good solubility in aprotic solvents and the viscosity was in the range of 0.72–0.89 dL/g. Also, the glass-transition temperature (Tg) of synthetic polymers was in the range of 214–273°C and 10% weight loss temperatures (T10%) for the synthesized compounds were in the temperature range of 280–492°C in N2, and the percentage of residual ash between 61 and 74%. The adsorption rate of Hg2+, Co2+, Pb2+, Cr2+, and Cd2+ metal ions by PA containing terephthalic acid (PAT) and its nanocomposite (NCPAT) showed that nanocomposite has a better performance compared to PAT. The highest and lowest removal efficiency was related to Hg2+ and Pb2+ ion, respectively. Finally, antibacterial test results against Gram-positive and Gram-negative bacteria showed favorable inhibitory effects of all the synthesized polymers.

Oxidation of BINOLs by Hypervalent Iodine Reagents: Facile Synthesis of Xanthenes and Lactones

Xanthene derivatives have broad applications in medicines, fluorescent probes, dyes, food additives, etc. Therefore, much attention was focused on developing the synthetic methods to prepare these compounds. Binaphthyl‐based xanthene derivatives were prepared through the oxidation of BINOLs promoted by the hypervalent iodine reagent iodosylbenzene (PhIO). Nine‐membered lactones were obtained through a similar oxidative reaction when iodoxybenzene (PhIO₂) was used. Additionally, one‐pot reactions of BINOLs, PhIO and nucleophiles such as alcohols and amines were also investigated to provide alkoxylated products and amides in good to excellent yields.

Bipyridine containing poly(amic-acid)s: Synthesis, characterization, and sorption behavior toward the Ni (II) ions

New poly(amic-acid)s sorbents, bearing bipyridine chelating groups, were synthesized by reaction of benzophenonetetracarboxylic dianhydride (BTDA) with different percentages of 4,6-bis(4-aminophenyl)-2,2′-bipyridine (BAPB), and 1,4-phenylene diamine (PPD) and were characterized by FTIR and 1HNMR spectroscopies. Because of the imidization of these poly(amic-acid)s after about 10% weight loss, their thermal stability was raised to about 500°C. The glass transition temperatures of these polymers were in the range of 154–166°C. The sorption of Ni(II) by these sorbents from the aqueous solutions was investigated by varying different parameters such as the contact time, pH, and sorbent dosage. Results indicated that the optimum efficiencies of these sorbents toward Ni(II) were at 25°C, at pH = 4 and after about 75 min. According to the Langmuir equation, the maximum uptake capacity ( qm) of PAA30/70 as a best sorbent for nickel was 14.66 mg.g−1. The modeling results confirmed the pseudo-second-order sorption for the metal ion. The morphology of these sorbents before and after sorption of Ni(II) was investigated using Scanning Electron Microscopy and the results confirmed the porous structure of these sorbents.

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Xanthenes in Medicinal Chemistry - Synthetic strategies and biological activities

BACKGROUND

Xanthenes are a special class of oxygen-incorporating tricyclic compounds. Structurally related to xanthones, the presence of different substituents in position 9 strongly influences their physical and chemical properties, as well as their biological applications. This review explores the synthetic methodologies developed to obtain 9H-xanthene, 9-hydroxyxanthene and xanthene-9-carboxylic acid, as well as respective derivatives, from simple starting materials or through modification of related structures. Azaxanthenes, bioisosteres of xanthenes, are also explored. Efficiency, safety, ecological impact and applicability of the described synthetic methodologies are discussed. Synthesis of multi-functionalized derivatives with drug-likeness properties are also reported and their activities explored. Synthetic methodologies for obtaining (aza)xanthenes from simple building blocks are available, and electrochemical and/or metal free procedures recently developed arise as greener and efficient methodologies. Nonetheless, the synthesis of xanthenes through the modification of the carbonyl in position 9 of xanthones represents the most straightforward procedure to easily obtain a variety of (aza)xanthenes. (Aza)xanthene derivatives displayed biological activity as neuroprotector, antitumor, antimicrobial, among others, proving the versatility of this nucleus for different biological applications. However, in some cases their chemical structures suggest a lack of pharmacokinetic properties being associated with safety concerns, which should be overcome if intended for clinical evaluation.

Novel poly(imide-ether)s based on xanthene and a corresponding composite reinforced with a GO grafted hyperbranched polymer: fabrication, characterization, and thermal, photophysical, antibacterial and chromium adsorption properties

High-performance polyimides (PIs) with ether linkages and trifluoromethyl (–CF₃) groups based on xanthene were designed and synthesized via a polycondensation reaction of novel diamine monomers with available aromatic dianhydrides.