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    Fluorine/phenyl chelated boron complexes: Synthesis, fluorescence properties and catalyst for transfer hydrogenation of aromatic ketones
    (Elsevier Science Sa, 2014) Kilic, Ahmet; Aydemir, Murat; Durgun, Mustafa; Meric, Nermin; Ocak, Yusuf Selim; Keles, Armagan; Temel, Hamdi
    The synthesis of salen/salan ligands (L-1 and L-2) and their fluorine/phenyl chelated boron complexes [L(1,2)BF2] or [L(1,2)BPh2] is described in this paper. The fluorine/phenyl chelated boron complexes were synthesized from the reaction of BF3 center dot OEt2 or BPh3 with the corresponding ligands in different solvent. The boron complexes display high stability and can be handled in air due to the presence of coordinative B <- N and covalent B-O bonds in their structures. The salen/salan ligands (designated as salan, a saturated version of the corresponding salen ligands) and their fluorine/phenyl chelated boron complexes have been characterized by H-1, C-13 NMR and F-19 NMR spectra, elemental analysis, FT-IR spectra, UV-vis spectra, LC-MS spectra, melting point and fluorescence spectroscopy. The fluorescence efficiencies of BF2-chelate boron complexes are greatly improved compared to those of the BPh2-chelate boron analogs based on the same salen/salan ligands, probably due to the enhanced conjugation degree of the diphenyl boron chelation, which can effectively prevent molecular aggregation. The boron complexes [L(1,2)BF2] or [L(1,2)BPh2] were also applied to the transfer hydrogenation of aromatic ketones to the corresponding alcohol derivatives in the presence of iso-PrOH as the hydrogen source. Catalytic studies showed that all complexes are good catalytic precursors for transfer hydrogenation of aryl alkyl ketones in 0.1 M iso-PrOH solution. This transfer hydrogenation is characterized by low reversibility under these conditions. (C) 2014 Elsevier B.V. All rights reserved.
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    Synthesis, spectroscopic and catalytic properties of some new boron hybrid molecule derivatives by BF2 and BPh2 chelation
    (Pergamon-Elsevier Science Ltd, 2015) Kilic, Ahmet; Alcay, Ferhat; Aydemir, Murat; Durgun, Mustafa; Keles, Armagan; Baysal, Akin
    A new series of Schiff base ligands (L-1-L-3) and their corresponding fluorine/phenyl boron hybrid complexes [LnBF2] and [LnPh2] (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 (H-1, C-13 and F-19), 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 pi ->pi* 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 0.1 M 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. (C) 2015 Elsevier B.V. All rights reserved.