Murat Aydemir

Synthesis, spectroscopic and catalytic properties of some new boron hybrid molecule derivatives by BF2 and BPh2 chelation.

A new series of Schiff base ligands (L1-L3) and their corresponding fluorine/phenyl boron hybrid complexes [LnBF2] and [LnBPh2] (n=1, 2 or 3) have been synthesized and well characterized by both analytical and spectroscopic methods. The Schiff base ligands and their corresponding fluorine/phenyl boron hybrid complexes have been characterized by NMR ((1)H, (13)C and (19)F), FT-IR, UV-Vis, LC-MS, and fluorescence spectroscopy as well as melting point and elemental analysis. The fluorescence efficiencies of phenyl chelate complexes are greatly red-shifted compared to those of the fluorine chelate analogs based on the same ligands, presumably due to the large steric hindrance and hard π→π(∗) transition of the diphenyl boron chelation, which can effectively prevent molecular aggregation. The boron hybrid complexes were applied to the transfer hydrogenation of acetophenone derivatives to 1-phenylethanol derivatives in the presence of 2-propanol as the hydrogen source. The catalytic studies showed that boron hybrid complexes are good catalytic precursors for transfer hydrogenation of aromatic ketones in 0.1M iso-PrOH solution. Also, we have found that both steric and electronic factors have a significant impact on the catalytic properties of this class of molecules.

Chiral phosphinites as efficient ligands for enantioselective Ru(II), Rh(I) and Ir(III)-catalyzed transfer hydrogenation reactions

Metal-catalyzed enantioselective transfer reduction of ketones to enantiomerically enriched chiral alcohols has recently attracted attention. Therefore, a series of methyl alkyl or alkyl/aryl ketones have been reduced by using Ru(II), Rh(I) and Ir(III) catalysts based on C2-symmetric chiral ferrocenyl phosphinite ligands. The corresponding optically active secondary alcohols were obtained in excellent conversions and moderate-to-good enantioselectivities. The best results were obtained with an iridium catalyst, giving up to 98% conversion and 80% ee.

Different Hemi-Salen/Salan Ligand Containing Binuclear Boron-Fluoride Complexes: Synthesis, Spectroscopy, Fluorescence Properties, and Catalysis

ABSTRACT A family of hemi-salen (L1H–L6H) and hemi-salan (L1aH–L2aH) ligands-based N,O-chelated binuclear boron-fluoride [Ln(BF2)2] (n = L1–L6 or L1a–L2a) complexes have been prepared and characterized by a variety of spectroscopic techniques (1H, 13C and 19F NMR, FT-IR, UV-Vis, LC-MS, and fluorescence spectra) and elemental analysis. All of the binuclear boron-fluoride complexes exhibit strong absorption bands due to S0→S1 transitions and strong fluorescence properties were observed at room temperature in the solution. The binuclear boron complexes containing two naphthyl groups are significantly red-shifted in comparison with the other binuclear boron-fluoride complexes. After the structures are characterized, these hemi-salen and salan ligand-based N, O-chelated binuclear boron-fluoride complexes were utilized to the transfer hydrogenation of the different acetophenone derivatives conversion to 1-phenylethanol derivatives as catalysts.

Amine-functionalized graphene nanosheet-supported PdAuNi alloy nanoparticles: efficient nanocatalyst for formic acid dehydrogenation

Formic acid (HCOOH), a major by-product of biomass processing with high energy density, stability and non-toxicity, has a great potential as a safe and a convenient liquid hydrogen (H2) storage material for combustion engines and fuel cell applications. However, high-purity hydrogen release from the catalytic decomposition of aqueous formic acid solution at desirable rates under mild conditions stands as a major challenge that needs to be solved for the practical use of formic acid in on-demand hydrogen generation systems. Described herein is a new nanocatalyst system comprised of 3-aminopropyltriethoxysilane-functionalized graphene nanosheet-supported PdAuNi alloy nanoparticles (PdAuNi/f-GNS), which can reproducibly be prepared by following double solvent method combined with liquid-phase chemical reduction, all at room temperature. PdAuNi/f-GNS selectively catalyzes the decomposition of aqueous formic acid through the dehydrogenation pathway (∼100% H2 selectivity), in the absence of any promoting additives (alkali formates, Bronsted bases, Lewis bases, etc.). PdAuNi/f-GNS nanocatalyst provides CO-free H2 generation with a turnover frequency of 1090 mol H2 mol metal−1 h−1 in the additive-free dehydrogenation of formic acid at almost complete conversion (≥92%) even at room temperature. The catalytic activity provided by PdAuNi/f-GNS nanocatalyst is higher than those obtained with the heterogeneous catalysts reported to date for the additive-free dehydrogenation of formic acid. Moreover, PdAuNi/f-GNS nanoparticles show high durability against sintering, clumping and leaching throughout the catalytic runs, so that the PdAuNi/f-GNS nanocatalyst retains almost its inherent catalytic activity and selectivity at the end of the 10th recycle.

Developments in transfer hydrogenations of aromatic ketones catalyzed by boron compounds

Abstract Boron complexes BL1 and BL2 were prepared from O-donor ligands, 2,2′-(1E,1′E)-(ethane-1,2-diylbis(azan-1-yl-1-ylidene))bis(methane-1-yl-1-ylidene)diphenol (L1) and 2,2′-(propane-1,3-diylbis(azan-1-yl-1-ylidene))bis(methane-1-yl-1-ylidene)diphenol (L2). The complexes were fully characterized by 1H and 13C NMR, LC-MS/MS, TGA/DTA, UV-Vis, elemental analysis, SEM, and FTIR. The transfer hydrogenation of acetophenone derivatives was investigated by the boron complexes in the presence of isoPrOH, as the hydrogen source, under basic condition with NaOH. The results showed that the boron complexes were promising catalytic precursors for transfer hydrogenation of aromatic ketones in 0.1 M isoPrOH solution (up to 99%). Both steric and electronic factors of this class of molecules had a significant impact on the catalytic properties.

p(HEMA)-Pd(II) and p(HEMA-MAH)-Pd(II) Microspheres: Efficient, Recyclable and Ligand-Free Catalyst for Suzuki-Miyaura Cross-Coupling Reaction in Water

In this study, the authors report the synthesis and characterization of new poly(hydroxyethyl methacrylate) palladium(II) (p(HEMA)-Pd(II)) and poly(hydroxyethyl methacrylate-N-methacryloyl-(L)-histidine methyl ester) palladium(II), p(HEMA-MAH)-Pd(II) microsphere catalysts, and their catalysis in Suzuki-Miyaura coupling reactions of aryl bromides with phenylboronic acid in water. The microsphere catalysts were characterized by SEM, ICP-MS, FTIR, and diffuse-reflactance UV-visible spectroscopy. The p(HEMA)-Pd(II) and p(HEMA-MAH)-Pd(II) microsphere catalysts were active catalysts in Suzuki-Miyaura coupling reactions of arylbromides with phenylboronic acid affording biphenyls in high yield. Recycling experiments showed that the p(HEMA)-Pd(II) and p(HEMA-MAH)-Pd(II) microsphere catalysts could be used seven or ten times with essentially no loss in activity in the Suzuki-Miyaura coupling reactions.

Influence of temperature and light intensity on Ru(II) complex based organic-inorganic device

An organic-inorganic junction was fabricated by forming [Ru(Cy2PNHCH2-C4H3O)(η6-p-cymene)Cl2] complex thin film using spin coating technique on n-Si and evaporating Au metal on the film. It was seen that the structure had perfect rectification property. Current-voltage (I-V) measurements were carried out in dark and under various illumination conditions (between 50-100 mW/cm2) and with the temperature range from 303 to 380 K. The structure showed unusually forward and reverse bias temperature and light sensing behaviors. It was seen that the current both in forward and reverse bias increased with the increase in light intensity and temperature.