Turgay Seçkin

Synthesis and immobilization of N-heterocyclic carbene complexes of Ru(II): catalytic activity and recyclability for the furan formation

Abstract Synthesis, characterization and immobilization of ruthenium(II) complexes of the type [RuCl 2 L(η 6 -arene)] (L= , arene= p -cymene, 3 and arene=C 6 Me 6 , 4 ) and [RuCl 2 L] (L=η 1 -carbene-η 6 -arene bidentate ligand, ), 5 , morphologically different silicas by sol–gel method are described and their reactivity and recyclability in the furan formation were also reported.

Pressurized liquid extraction of phenolic compounds from Anatolia propolis and their radical scavenging capacities.

Propolis samples from important honey producing locations of Anatolia namely; Bingol (BG), Rize (RZ), Tekirdag (TK) and Van (VN), were evaluated for their antiradical capacities, total phenolic contents and individual phenolic compounds which was recovered by means of pressurized liquid extraction (PLE). Several extraction parameters of PLE such as; temperature, pressure, solvent type, extraction time and cell size were investigated for their effects on the extraction performances. The results showed that, 40 °C, 1500 psi, Ethanol:water:HCl; (70:25:5, v/v/v) containing 0.1% tert-butylhydroquinone (tBHQ) as solvent, three extraction cycles within 15 min, and a cell size of 11 mL was the most favorable PLE operating conditions. Results of the tests performed to designate the success of the polyphenol analysis showed that the recovery was in the range of 97.2% and 99.7%. Major phenolic compounds in all samples were found to be gallocatechin (GCT), catechin (CT), epicatechin gallate (ECTG), caffeic acid (CA), chlorogenic acid (ChA), and myricetin (Myr). ChA level of BG propolis was 4.5, 3 and 23 times higher than that of RZ, TK and VN region, respectively. Antiradical tests showed that all propolis samples have superior antiradical capacities up to 500 mg Trolox equivalent activity per gram of extract.

The grafting of Rhodamine B onto sol-gel derived mesoporous silicas

Amorphous meseporous silica, silica foams and silica nanotubes have been prepared by the controlled hydrolysis of tetraethoxysilane in various environments. A self-similar structure was obtained in all cases. Rhodamine B was post grafted onto the meseporous silica foam which has been modified with γ-glycidyloxypropyl trimethoxysilane. The grafting and post grafting efficiency of γ-glycidyloxypropyl trimethoxysilane as well as the post grafting efficiency of Rhodamine B on meseporous silica foam were studied, respectively. Basic physicochemical properties of the modified particles are given. When the hybrid pigments were exposed to UV radiation pulses, the emission of the hybrid pigments was increased.

Preparation and characterization of a clay-polyvinylpyridinium matrix for the removal of bacterial cells from water

Polyvinylpyridinium salts were immobilized onto a clay matrix and were then tested for their antibacterial properties. The clay-polyvinylpyridinium matrix was prepared by the copolymerization of γ-methacryloxypropyltriethoxy silane bonded covalently to clay and 4-vinylpyridine and subsequent quaternization with benzyl halides. Suspension tests for antibacterial properties of the immobilized bactericide against Escherichia coli, Staphylococcus aureus, and Pseudomonas aeruginosa demonstrated the high activity of the pyridinium salts that are bonded to the polyacrylate spacer. Advantageously, these insoluble clay-polymer bactericides could be applied without any contamination by the substrate.

Synthesis and properties of novel polyimides from dichloro (1,3-p-dimethylaminobenzylimidazolidine-2-ylidene) p-cymene ruthenium (II)

A novel diamine derivative, dichloro (1,3-p-dimethylaminobenzylimidazolidine-2-ylidene) p-cymene ruthenium (II), bearing a potential site for imide formation, was prepared starting from p-dimethylaminobenzaldehyde. It was used as a monomer to prepare polyimides with several dianhydrides via a one-stage procedure without going through tedious steps. The polyimides have inherent viscosities that range from 1.18 to 1.24 dl/g in N-methyl-2-pyrrolidinone at 30°C. These new polymers are soluble in polar aprotic solvents. The polymeric catalyst was added to (Z)-3-methylpent-2-en-4-yn-1-ol without a solvent and the pure furan was isolated by distillation under reduced pressure and GC determined the conversion of the starting enynol.

Synthesis and characterization of N-substituted 1,4,5,6-tetrahydropyrimidine containing functional polymers as SO2 and CO2 sorbents

Novel vinyl monomers containing 1,4,5,6-tetrahydropyrimidine were prepared by the reaction of N-substituted-1,3-diaminopropane with N,N-dimethyl-formamide dimethylacetal, which gave 1-alkyl or aryl substituted 1,4,5,6-tetrahydropyrimidines, Alkylation of the tetrahydropyrimidine derivatives by chloromethylstyrene produces the N-methyl-N′-vinyl benzyl-1,4,5,6-tetrahydropyrimidinium chloride in high yields. These monomers were readily polymerized in dimethylformamide by AIBN at 80°C. Homopolymers and soluble linear copolymers were prepared and copolymerization parameters were rationalized. Further, insoluble terpolymers prepared from these monomers, styrene and divinylbenzene were tested for the sorption of the weakly acidic gases gave excellent results.

Synthesis and characterization of novel polyacrylate-clay sol-gel materials

Organo-functional silanes which were able to form chemical bonds with kaolinite and could also have an affinity to the materials of concern here, were studied by the sol-gel process. Polymethacrylate with trialkoxy silyl functional groups were prepared, hydrolysed and co-condensed with kaolinite. The progress of the hydrolysis, which proceeded very slowly, was followed by Karl-Fischer titration. Thermal behavior was investigated by differential thermal analysis. The extent of the reaction leading to network formation was qualitatively followed by Fourier transform-infrared spectroscopy and X-ray diffraction. Free-radical polymerization was carried out ultrasonically in the presence of a catalyst. Trimethoxy silane end-capped silane was found to be covalently bonded to kaolinite. The copolymers, with various amounts of kaolinite, were then hydrolysed and co-condensed in the presence of a catalyst to yield sol-gel materials which have a controllable combination of properties of both the polymer and kaolinite.

Synthesis, Characterization and Dielectric Properties of Rodlike Zinc Oxide-Polyimide Nanocomposites

Novel polyimide-rodlike zinc oxide hybrid nanocomposite (PI-RL-ZnO) has been developed from the poly (amic acid) with different weight percentages (1, 3, 5 wt%) of using N-methyl-2-pyrrolidone (NMP) and N,N-dimethylacetamide (DMAc) as aprotic solvents. The prepared zinc oxide-polyimide nanocomposites were characterized for their structure, morphology, and thermal behavior employing Fourier transform infrared spectroscopy (FTIR), scanning electron micrograph (SEM), transmission electron micrograph (TEM), X-ray diffraction (XRD) and thermal analysis (DTA/TGA/DSC) techniques. These studies showed the homogenous dispersion of zinc oxide in the polyimide matrix with an increase in the thermal stability of the composites on zinc oxide loadings. More importantly, we intend to explore the possibility of incorporating ZnO particles through dispersion into the polyimide network to achieve the polyimide hybrid with lower dielectric constant (low-k). The lowest dielectric constant achieved of the PI-RL-ZnO material is 2.82 by incorporating 5 wt% ZnO (pure PI, k = 3.22). The reduction in the dielectric constants of the PI-RL-ZnO hybrids can be explained in terms of creating ZnO particles and the free volume increase by the presence of the ZnO particles resulting in a loose PI structure.

Novel Type of Metal-Containing Polyimides for the Heck and Suzuki–Miyaura Cross-Coupling Reactions as Highly Active Catalysts

Novel palladium (II)-containing polyimides with exceptional catalytic properties for the Heck and Suzuki–Miyaura cross-coupling reactions were prepared from Pd(II)-α-bis(imine) complex and the corresponding dianhyrides. The glass transition temperatures (Tg) of the polymers ranged from 169 to 241°C. The temperatures at which 10% weight loss occurred in air ranged from 415 to 579°C. Polyimides based on the palladium (II) complex were tested for catalytic activity in the Heck coupling reaction between styrene and several aryl halides and the Suzuki coupling reaction between phenylboronic acid and several aryl halides. The negative effects (e.g., expense, low reaction rates, air-sensitivity) experienced by using phosphines, particularly electron-rich phosphines, as catalysts in large scale applications is overcome by using polymer supported catalysis.

Synthesis and stimuli-responsive properties of the phenanthroline based metallo-supramolecular polymers

A series of functional metallo-supramolecular materials based on polyhedral oligomeric silsesquioxane (POSS) and phenanthroline ligand were prepared using a two-step approach. Firstly, using a phenanthroline ligand, an amino-functionalized transition metal complex was prepared by tin(II) chloride. In the second step, this metal complex was subsequently reacted with the octakis(3-chloropropyl)octasilsesquioxane, resulting for the metallosupramolecular polymers bearing POSS structure. All the synthesized compounds were fully characterized by spectroscopic analysis, thermal and electron microscopy techniques. Stimuli responsible properties of metallo-supramolecular materials were also investigated the reversibility upon external factors, such as electrochemical or the addition of competitive complexing ligands by electroanalytic techniques and UV–Vis spectroscopy. The electro- and chemo-responsive properties of the metallo-supramolecular materials were also improved. As a result, prepared phenanthroline-functionalized polyhedral silsesquioxane are good candidates for electronic, opto-electronic, and photovoltaic applications as a smart stimuli-responsive material.