New phosphine-amino-alcohol tridentate ligands for ruthenium catalyzed asymmetric transfer hydrogenation of ketones
Altan, Orhan | Yılmaz, Mustafa Kemal
New phosphine-amino-alcohol tridentate ligands (3a-c) and six new ruthenium complexes (4a-c and 5a-c) were synthesized and characterized. Catalytic activities of the metal complexes were tested on aryl alkyl ketones. All of the substrates were converted to related sec-alcohols in excellent yields (up to 99%), but enantioselectivities were insufficient (up to 40% ee). Despite the catalytic performance of 5a-c complexes can be considered as better than 4a-c, actually the catalytic activity of the complexes has been differed according to substrate. The ketones with less positive carbonyl carbons tend to give S-configuration with 5a-c and R-configuration with 4a-c. The catalytic performance of the complexes was rationalized by means of DFT calculations.
Nanostructured Photocatalysts Chapter 15 - Black phosphorus-based photocatalysts for energy and environmental applications
Altan, Orhan
Photocatalysis using semiconductor materials to conduct chemical reactions more efficiently with the aid of sunlight irradiation is foreseen as a promising solution to combat the energy and environmental pollution crisis that the world is facing at present. Finding a suitable semiconductor material that harvests a large portion of the sunlight spectrum with high photocatalytic efficiency lies in the heart of photocatalysis. In this regard, black phosphorus (BP), a rising star two-dimensional (2D) semiconducting material, has recently been regarded as an abundant, nontoxic, metal-free, and cheap photocatalyst with a suitable bandgap and broad light absorption ability. In this chapter, after the introduction of the general properties and synthesis of BP, the photocatalytic efficiency of BP a...
Boosting formic acid dehydrogenation via the design of a Z-scheme heterojunction photocatalyst: The case of graphitic carbon nitride/Ag/Ag3PO4-AgPd quaternary nanocomposites
Altan, Orhan
The development of an efficient, eco-friendly, practical, and selective way to decompose formic acid (FA) into H2 and CO2 is crucial for the utilization of FA as a chemical hydrogen storage material in hydrogen economy. In this regard, photocatalytic FA dehydrogenation attracts great attention owing to its potential to meet the above-mentioned requirements. Interestingly, there is no example of heterojunction photocatalyst that tunes the hole potential of the semiconductor, resulted in a better photocatalytic activity. We report herein for the first time the design and fabrication of a novel Z-scheme heterojunction photocatalyst for FA dehydrogenation, denoted as g-CN/Ag/Ag3PO4-AgPd comprising graphitic carbon nitride (g-CN) and Ag3PO4 semiconductors, Ag and AgPd alloy nanoparticles (NPs)....
The influence of band bending phenomenon on photocatalytic Suzuki-Miyaura coupling reaction: The case of AgPd alloy nanoparticles supported on graphitic carbon nitride
Altan, Orhan
The development of solar-powered systems for applications other than energy, such as photocatalytic organic reactions, will benefit in the resolution of environmental issues while also lowering production costs. In this study, the photocatalytic activity of g-CN(G)-AgPd, which was prepared by synthesizing AgPd alloy nanoparticles (NPs) on g-CN, was investigated in the Suzuki-Miyaura coupling (SMC) reaction. The photocatalytic activity of g-CN(G)-AgPd in an ethanol/water mixture at ambient temperature was discovered to be among the highest ever recorded. Under vis-light illumination, g-CN(G)-AgPd converted all of the aryl iodides and most of the aryl bromides investigated to desired coupling products in 15 min with excellent isolated yields, and it was used at least five times without signi...
A rare example of the in situ formation of palladium nanoparticles: The emergence of catalytically active palladium nanoparticles from Pd (II) phosphine complexes in the Suzuki–Miyaura coupling reaction
Altan, Orhan
Suzuki–Miyaura coupling (SMC) reactions are one of the most promising routes for carbon–carbon bond formation. It is believed that metal complexes, particularly palladium complexes, are the most effective catalysts for this purpose. However, the catalysis nature whether it is homogenous or heterogeneous is under debate. It is commonly believed that a homogenous catalysis pathway is responsible for the catalytic activity when the phosphine ligands are present in the structure due to the strong phosphorus-metal interactions. In this study, Pd (II) complexes of phosphino-benzaldoxime ligands were synthesized, characterized, and tested in SMC reactions. Interestingly, it was found that the catalytic activity increased by 11 times when the amount of catalyst was reduced by 10-fold and increased...
The rational design of a graphitic carbon nitride-based dual S-scheme heterojunction with energy storage ability as a day/night photocatalyst for formic acid dehydrogenation
Altan, Orhan
Photocatalytic formic acid dehydrogenation (FAD) has been regarded as one of the most promising methods of producing H2 in a sustainable manner. In the photocatalytic FAD reaction, photogenerated holes play an important role in the reaction mechanism and thus in the efficiency of photocatalysts. However, the design of photocatalytic systems capable of generating high hole potential without compromising the reducing ability of the photocatalyst is extremely rare for the FAD reaction. In this respect, we report herein a novel and highly efficient heterojunction photocatalyst composed of 2D graphitic carbon nitride, 2D MnO2, 1D MnOOH, and 0D PdAg alloy nanoparticles, denoted as GCN/MnO2/MnOOH-PdAg, that can create high reduction and oxidation potentials via a dual S-scheme heterojunction. The...
Synthesis and characterization of bis(diphenylphosphinomethyl)amino ligands and their Ni(II), Pd(II) complexes: Application to hydrogenation of styrene
Altan, Orhan
Transition metal complexes of Ni(II) and Pd(II) with ditertiary bis(diphenylphosphinomethyl)amino ligands, (Ph2PCH2)2NC(CH3)3 (1) and [(Ph2PCH2)Nm-PhSO3]Na (2) (Ph = phenyl), have been synthesized in good yields under nitrogen atmosphere by Schlenk technique. All complexes have been characterized using elemental analyses and spectroscopic techniques such as atomic absorption, FT-IR, and NMR (1H, 31P). Atomic absorption spectroscopic analysis showed that the reactions of ligands 1 and 2 with NiCl2 ⋅ 6H2O and [PdCl2(COD)] occurred in 1:1 molar ratio. The metal complexes [NiCl2(Ph2PCH2)2Nm-PhSO3Na] (4) and [PdCl2(Ph2PCH2)2Nm-PhSO3Na] (6) were found to be soluble in ethanolic and aqueous solutions, as well as slightly soluble in water. Electrochemical behaviors of complexes were investigated b...
Pd(II) complexes of novel phosphine ligands: Synthesis, characterization, and catalytic activities on Heck reaction
Altan, Orhan
Novel phosphine oxides, (((3-methylpyridin-2-yl)amino)methyl)diphenylphosphine oxide (1) and diphenyl((pyrazin-2-ylamino)methyl)phosphine oxide (2), were synthesized and characterized. Phosphines ligands (3 and 4) were obtained by the reduction of 1 and 2 with AlH3, monitored by 31P NMR spectroscopy. Pd(II) complexes of 3 and 4 were synthesized and characterized (5 and 6). The catalytic activity of 5 and 6 was tested on the reaction of styrene with both activated and deactivated aryl bromides in air. The results of the catalytic experiments were discussed through DFT calculations.
Enhancement of photocatalytic activity of carbon nitride/black phosphorus/tungsten disulfide (CN/BP/WS2) heterojunctions via nickel doping in the hydrogen evolution reaction
Altan, Orhan
The complementary properties of mesoporous graphitic carbon nitride (m-CN) and black phosphorus (BP) as non-metallic semiconductors offer many opportunities for the rational design of efficient photocatalysts for the photocatalytic hydrogen evolution reaction (HER). However, pristine m-CN and BP exhibit significant photoinduced charge carrier recombination rates and weak light absorption, resulting in a low photocatalytic HER activity. To overcome these problems and improve their photocatalytic HER activities, rational design of heterojunctions is one of the most efficient ways. Here, we present for the first time the ternary m-CN/BP/WS2 dual S-scheme heterojunctions, prepared by combining as-prepared m-CN/BP hybrids with tungsten disulfide (WS2). Encouragingly, the ternary m-CN/BP/WS2 het...
Impact of graphitic carbon nitrides synthesized from different precursors on Schottky junction characteristics
Altan, Orhan
Graphitic carbon nitride (g-CN) has gained wide interest in many areas, such as energy and the environmental remediation as a layered polymeric semiconductor that allows the formation of catalytically active Schottky junctions due to its proper electronic band structure. Interestingly, although it is known that the precursors used in the synthesis, can influence the properties of the g-CN, no detailed study on these effects on Schottky junctions could be found in the literature. In this research, the effects of g-CNs synthesized by thermal polycondensation of different precursors on the photocatalytic efficiency of Schottky junctions were investigated. For this purpose, urea, thiourea, melamine, and guanidine hydrochloride were used as different precursors, while the photocatalytic dehydro...