Yakup Baran

Removal of toxic metal ions with magnetic hydrogels.

Hydrogels, based on 2-acrylamido-2-methyl-1-propansulfonic acid (AMPS) were synthesized via photopolymerization technique and used for the preparation of magnetic responsive composite hydrogels. These composite hydrogels with magnetic properties were further utilized for the removal of toxic metal ions such as Cd(II), Co(II), Fe(II), Pb(II), Ni(II), Cu(II) and Cr(III) from aqueous environments. It was revealed that hydrogel networks with magnetic properties can effectively be utilized in the removal of pollutants. The results verified that magnetic iron particle containing p(AMPS) hydrogel networks provide advantageous over conventional techniques. Langmuir and Freundlich adsorption isotherms were applied for toxic metal removal and both isotherms were fit reasonably well for the metal ion absorptions.

Synthesis, spectroscopic, and thermal properties of some azomethine complexes of Cu(II), Ni(II), and Pt(II)

Four polydentate azomehines and their mono- and binuclear Pt(II), Cu(II), and Ni(II) complexes were synthesized and characterized. The resulting complexes were characterized by FTIR, magnetic measurements, elemental analysis, conductivity measurements, and thermal analysis. Electronic spectra and magnetic susceptibility measurements sustain the proposed distorted square-planar structures for the copper complexes. The electronic spectra display the characteristic pattern of square-planar stereochemistry for the other complexes. The thermal analyses have evidenced the thermal intervals of stability and also the thermodynamic effects that accompany them. Azomethine complexes have a similar thermal behavior for the selected metal ions. The decomposition processes as water elimination, chloride anion removal as well as degradation of the organic ligands were observed.

Copper and cobalt complexes of octadentate azamacrocycles: spectrophotometric titration, stopped-flow kinetics and crystallographic study.

Details of complex formation kinetics are reported for tetrakis(2-hydroxyethyl) substituted cyclen (L(1)) and cyclam (L(2)) with Cu(II) and Co(II). Stopped-flow kinetics and spectroscopic titration methods were employed for the activation parameters and stability constants, respectively. X-ray studies revealed that the pendant 2-hydroxyethyl groups are not equivalent: two are folded over the macrocycle and maintained by intramolecular hydrogen bonds while the others are extended and pointed away from the macrocyclic cavity. Complex formation kinetics and spectroscopic titration were performed in aqueous acidic buffer solutions. Thermodynamic and kinetic parameters revealed that the ring size of the macrocycles plays an extremely important role for each metal ion studied. Stopped-flow kinetic measurements explained the mechanism of the complex formation process of both Cu(II) and Co(II) which proceed in outer-sphere interactions with ligands. There are two steps in the complex formation of the system studied. The initial step is a second order reaction between the metal ion and macrocycle with a second order rate constant.

Complexation, thermal and catalytic studies of N-substituted piperazine, morpholine and thiomorpholine with some metal ions

Several Cu(II), Pt(II) and Ni(II) complexes of N-substituted, piperazine (NN donor), morpholine (NO donor) and thiomorpholine (NS donor) derivatives were synthesized and their thermal behavior and catalytic activity in epoxidation reaction of cis-diphenylethylene were studied using oxygen sources NaOCl. The coordination compounds of Cu(II), Pt(II) and Ni(II) having general formula [MLCl]Cl, [ML2l]Cl2 or [ML]Cl2 with tetra coordinated geometry around metal ions have been isolated as solid. All the ligands and complexes were identified by spectroscopic methods and elemental analysis, magnetic measurements, electrical conductance and thermal analysis. A square planer structures have been proposed for all complexes. The thermal stability of the complexes discussed in terms of ligands donor atoms, geometry and central metal ions. The complexes have a similar thermal behavior for the selected metal ions. The thermogravimetric analyses suggest high thermal stability for most complexes followed by thermal decomposition in different steps. The decomposition processes were observed as water elimination, chloride anion removal and degradation of the organic ligands. Catalytic ability of the complexes were examined and found that all the complexes can effectively catalyze the epoxidation of cis-stilbene with NaOCl.

Synthesis, spectroscopic characterization, X-ray structure and DFT studies on 4-(2-hydroxyphenyl)-4,5,6,7-tetrahydro-1H-imidazo[4,5-c]pyridin-5-ium chloride hydrate.

The title molecular salt, 4-(2-hydroxyphenyl)-4,5,6,7-tetrahydro-1H-imidazo[4,5-c]pyridin-5-ium chloride hydrate (C(12)H(14)N(3)O(+)·Cl-·H(2)O), was synthesized and characterized by IR-NMR spectroscopy and single-crystal X-ray diffraction. In addition to the molecular geometry from X-ray experiment, the molecular geometry, vibrational frequencies and gauge-independent atomic orbital (GIAO) (1)H and (13)C NMR chemical shift values of the title compound in the ground state have been calculated using the density functional theory (DFT/B3LYP) method with the 6-31++G(d,p) and 6-311++G(d,p) basis sets, and compared with the experimental data. Besides, molecular electrostatic potential (MEP) distribution and non-linear optical properties of the title compound were investigated by theoretical calculations at the B3LYP/6-311++G(d,p) level.

Spectroscopic and structural properties of N-(acetamide) morpholinium bromide.

A new crystal of N-(acetamide) morpholinium (NAM) bromide has been prepared in methanol at room temperature and characterized by single crystal X-ray analysis, elemental analysis, GS-MS, FTIR, NMR((1)H,(13)C, DEPTH and HETCOR). The N-(acetamide) morpholinium crystallizes in the orthorhombic crystal system, Pnma with unit cell a=12.798(9) Å, b=7.222(5) Å, c=9.244(5) Å, β=90.00, V=854.4(9) Å(3), Z=4. The X-ray structure determination revealed that there are strong inner and intermolecular hydrogen bonds in the crystal.

Structure, Spectroscopic, Magnetic, Fluorescence, and Thermal Studies of Bis(perchlorate)tetrakis(pyrazole)copper(II)

The complex bis(perchlorate)tetrakis(pyrazole)copper(II) has been prepared and characterized by single crystal X-ray analysis, FT-IR, UV-VIS spectroscopy and thermal methods. [Cu(ClO4)2(pyzl)4] crystallizes in the monoclinic system, space group C2/c, with a = 14.5186(11), b = 9.9513(7), c = 15.8564(11) Å, β = 115.5290(10)° V = 2067.2(3) Å3 and z = 4. The molecular and crystal structure are stabilized by inter and intra molecular hydrogen bonds. The complex formation kinetics was studied at 310 nm. The activation parameters of the complex formation kinetics were determined as, ΔH#: 200 kJ/mol, ΔS#: 268 J/K. mol. The FT-IR spectra has been measured and assigned in the range of 4000-400 cm−1. The Cl-O and N-H stretching vibrations confirms the presence of intramolecular hydrogen bonds. The magnetic moment of the complex was found to be 1.73 BM. The fluorescence quenching of pyrazole by Copper(II) was also studied in methanol.

The stabilities and formation kinetics of some macrocycles with copper(II): crystal structures of some pendant arm macrocycles

Kinetics of complex formation and stability constants of tetra-(2-hydroxpropyl) substituted cyclam (L3) and cyclen (L4) with copper(II) have been studied in aqueous solution at room temperature. These data are compared to the corresponding parent compounds (cyclam L1 and cyclen L2) in an attempt to define the effect of pendant arm upon kinetics and stability constants of the complexes. The kinetics were observed by stopped-flow measurements followed at multiwavelengths. These ligands were chosen to furnish information concerning effect of pendant groups and cavity size on the kinetics and stability of the complexes. Stopped-flow and spectrophotometric titration techniques were used for evaluation of the kinetics and stability constants, respectively. The apparent rate constants increase as CuL3 > CuL4 > CuL1 > CuL2. Activation parameters and stability constants of the complexes were estimated. The effect of cavity size on the rate of reaction can be observed in CuL3 > CuL4 and CuL1 > CuL2 and the effect of pendant groups in CuL3 > CuL1 and CuL4 > CuL2. Mechanism of the complex formation reaction is proposed. The enhanced stability of the copper(II) complexes formed with L1 and L2 macrocyclic ligands is compared to those formed with analogous pendant arm species.

1,1'-(Piperazine-1,4-di-yl)dipropan-2-ol.

The asymmetric unit of the crystal contains one-fourth of the title compound, C10H22N2O2, with the centre of the piperazine ring located at a site of 2/m symmetry. The piperazine ring adopts a chair conformation. The methine and methylene C atoms of the 2-hydroxypropyl groups show symmetry-imposed disorder over two equally occupied and mutually exclusive sets of positions. Only intramolecular O—H⋯N contacts are observed.

Synthesis, complex formation kinetics and thermodynamic study of some acyclic polyamine and N2O2 ligands with copper(II)

The polydentate ligands, 3-(2-aminocyclohexylamino)-2-(2-aminocyclohexyl aminomethyl) propionic acid (L1 ), 4,7,10-triazatridecanedinitrile trihydrochloride (L2 ), and 2,2′-(ethane-1,2-diyl) bis(methylazanediyl) diethanol (L3 ) were prepared and their structures investigated by FT-IR, NMR, and MS. The kinetics of complex formation between Cu(II) and L1, L2, and L3 were investigated in acidic aqueous solutions using the stopped-flow method. The stability constants of the complexes were determined by spectrophotometric titration (T = 293 K, μ = 0.1 mol L−1 NaClO4), using a diode array UV-Vis spectrophotometer equipped with peristaltic pump and pH meter. The stability constants for the complexes were CuL1 > CuL2 > CuL3. Activation enthalpies (ΔH#) of these complexes were 55 kJ mol−1 for CuL1, 61 kJ mol−1 for CuL2, and 36 kJ mol−1 for CuL3, respectively.