Bahattin Yalçın

Influence of the Nature of the Metal Ion on the Rate of Reduction of Coordinated Azomethine Group

The kinetics of reduction of the azomethine bond in various Schiff bases and their transition metal complexes with sodium borohydride in dimethylformamide and ethanol solutions was studied. The reduction rate depends on both the structure of the starting Schiff bases and the nature of the metal ion. In transition metal N-phenylsalicylaldiminates, the rate of reduction of the azomethine group increases in the order Zn(II) < Ni(II) < Cu(II) < Co(II) < VO(II) < Mn(II). Similar trend is observed in other series of metal complexes with Schiff bases. The revealed trends are opposite to the Irving-Williams series of stability of complexes. This fact suggests that the major factor affecting the rate of reduction of the coordinated azomethine bond is the strength of its bonding with the metal ion. Depending on particular metal ion, the complexation can either decelerate or accelerate the reduction.

Nutrient dynamics and eutrophication in the Sea of Marmara: Data from recent oceanographic research

This work was implemented to study the physicochemical and biological characteristics of the Sea of Marmara and the Turkish straits (TSS: Bosporus and Dardanelles straits) for the period 2010-2013 and to calculate winter and summer fluxes of nutrients (nitrates, phosphates) between the Aegean and Black Seas through the TSS. The brackish Black Sea waters reach the Dardanelles Strait with modified biochemical properties. The salinity and phosphates of the surface waters increased westwards. Biologically labile nutrients of Black Sea origin are utilized through biological processes in the Marmara Sea. On the other hand, increase of nutrients due to land based sources has led to eutrophication problems in the area. The sub surface water layer of Mediterranean origin is oxygen depleted (saturation<30%) and rich in nutrients. Higher oxygen values indicated water mixing of the Sea of Marmara during winter 2012. Ammonium was the predominant form of inorganic nitrogen. The study area has been classified from Moderate to Bad trophic status. İzmit Bay also faced serious eutrophication problems together with hypoxic conditions below the halocline. Nutrient fluxes through the TSS showed temporal variation in the upper and lower layers related to changes in both nutrient concentrations and the water mass volume fluxes. Surface nitrates and phosphates outflux from the Sea of Marmara to the Aegean Sea was higher than the influx from the Black Sea through Bosporus strait, indicating high enrichment of nutrients in the Sea of Marmara from anthropogenic sources.

Composition, properties, and application of products formed in oxidation of polyethylene by nitric acid

Structure of products formed in polyethylene oxidation by nitric acid was studied by NMR, IR, and electronic absorption spectroscopies and derivatography.

Synthesis in water-free DMF, characterization, electrical, and gas sensing properties of bis(2-(2-aminoethylamino)ethanol)copper(II) dibromide

Abstract2-(2-Aminoethylamino)ethanol (L) reacts with cupric bromide in dimethylformamide to give a mononuclear complex of Cu(II) [L2Cu]Br2, with six-coordinate distorted octahedral geometry, in which two molecules of tridentate (N,N,O) ligand are involved. The structure was confirmed by spectroscopic methods, elemental and thermogravimetric analyses, and magnetic measurements. Optimization of possible configurations indicated the formation of the trans structure of the complex. Experimental results indicate that the investigated complex, bis[2-(2-aminoethylamino)ethanol] copper(II) bromide, behaves as a semiconductor in the studied temperature range of 298–388 K. Gas sensing properties of the film for the volatile organic compounds (VOCs): acetone, tetra-chloromethane, chloroform, ethanol, and methanol, were also investigated as a function of vapor concentration and temperature in dark. The film showed maximum sensitivity to tetrachloromethane and ethanol vapors at room temperature. Responses of the film to the tested gases are reversible.

Heterovalent trinuclear Co(III)-Co(II)-Co(III) complexes with N-(2-Carboxyethyl)salicylaldimines

The heterovalent trinuclear cobalt complexes [Co2IIIL4i · CoII(H2O)4] · nXmY (Li are deprotonated Schiff bases derived from substituted salicylaldehydes and β-alanine; i = 1–3) were obtained and characterized. An X-ray diffraction study of the trinuclear cobalt complex with N-(2-carboxyethyl)salicylaldimine showed that the central Co(II) ion and the terminal Co(III) ions are linked by bridging carboxylate groups. Either terminal Co(III) atom is coordinated to two ligand molecules. They form an octahedral environment consisting of two azomethine N atoms, two phenolate O atoms, and two O atoms of two carboxylate groups. The central Co(II) atom is coordinated to four water molecules and to two O atoms of two bridging carboxylate ligands involved in the coordination sphere of the terminal Co(III) atoms.

CCDC 1569923: Experimental Crystal Structure Determination

Related Article: Mansura Huseynova, Parham Taslimi, Ajdar Medjidov, Vagif Farzaliyev, Mahizar Aliyeva, Gulnar Gondolova, Onur Şahin, Bahattin Yalcin, Afsun Sujayev, Efe Baturhan Orman, Ali Riza Ozkaya, Ilhami Gulcin||Polyhedron|||doi:10.1016/j.poly.2018.08.026

CCDC 1556057: Experimental Crystal Structure Determination

Related Article: Mansura Huseynova, Parham Taslimi, Ajdar Medjidov, Vagif Farzaliyev, Mahizar Aliyeva, Gulnar Gondolova, Onur Şahin, Bahattin Yalcin, Afsun Sujayev, Efe Baturhan Orman, Ali Riza Ozkaya, Ilhami Gulcin|2018|Polyhedron|155|25|doi:10.1016/j.poly.2018.08.026

Synthesis, crystal structure and biological evaluation of spectroscopic characterization of Ni(II) and Co(II) complexes with N-salicyloil-N′-maleoil-hydrazine as anticholinergic and antidiabetic agents

[Ni(C11H9N2O5)2(H2O)2]•3(C3H7NO) (1) and [Co(C11H9N2O5)2(H2O)2]•3(C3H7NO) (2) are synthesized and characterized by elemental analysis, FT‐IR spectra, magnetic susceptibility, and thermal analysis. In addition, the crystal structure of Ni(II) complex is presented. Both complexes show distorted octahedral geometry. In 1 and 2, metal ions are coordinated by two oxygen atoms of salicylic residue and two nitrogen atoms of maleic amide residue from two ligands, and two oxygen atoms from two water molecules. In this paper, both compounds showed excellent inhibitory effects against human carbonic anhydrase (hCA) isoforms I, and II, α‐glycosidase, acetylcholinesterase (AChE), and butyrylcholinesterase (BChE). Compounds 1 and 2 had Ki values of 18.36 ± 4.38 and 26.61 ± 7.54 nM against hCA I and 13.81 ± 3.02 and 29.56 ± 6.52 nM against hCA II, respectively. On the other hand, their Ki values were found to be 487.45 ± 54.18 and 453.81 ± 118.61 nM against AChE and 199.21 ± 50.35 and 409.41 ± 6.86 nM against BChE, respectively.

Redox reactions between metal nitrates and polyols with the formation of nanopowders

The reduction of metal nitrates (Cu(NO3)2 · 6H2O, AgNO3, and Ni(NO3)2 · 6H2O) by polyols under hydrothermal conditions at temperatures of 150–250°C was studied. The possibility of synthesizing copper, silver, and nickel powders with average particle sizes of 10 to 150 nm depending on the concentration of initial reagents, the temperature, and the nature of a reducer was established using X-ray diffraction analysis and atomic force microscopy. Lanthanide and alkali-earth nitrates were shown to form highly dispersed powders of metal carbonates with an average particle size of ∼23 nm under similar conditions.