Makale 2000-2009 yılları
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Browsing Makale 2000-2009 yılları by All Authors "Elmalı, Ayhan"
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Item A theoretical analysis of the explanation of the significant differences in antiferromagnetic interactions between homologous μ-alkoxo and acetate bridged dicopper(II) complexes: ab initio and semi-empirical calculations(Elsevier, 2004-07) Zeyrek, C. Tuğrul; Elmalı, Ayhan; Elerman, Y.; 0000-0001-6744-7841; TAEK-ANAEMA magnetostructural classification of dimmers, containing the Cu (μ-alkoxo) Cu core, based on data obtained from X-ray diffraction analysis reported in the literature has been performed. In these complexes, the local geometry around the copper ions is generally a square planar and each copper ion is surrounded by one N atom and three O atoms. The influence of the overlap interactions between the bridging ligands and the metal (Cu) d orbitals on the super-exchange coupling constant has been studied by means of ab initio Restricted Hatree–Fock molecular orbital calculations. The interaction between the magnetic d orbitals and highest occupied molecular orbitals of the acetate oxygens has been investigated in homologous μ-acetato-bridged dicopper(II) complexes which have significantly different −2J values (the energy separation between the spin-triplet and spin-singlet states). In order to determine the nature of the fronter orbitals, Extended Hückel molecular Orbital calculations are also reported. Ab initio restricted Hartree–Fock calculations have shown that the acetato bridge and the alkoxide bridge contribute to the magnetic interaction countercomplementarily to reduce antiferromagnetic interaction.Item Crystal structure and magnetic exchange interaction in a binuclear copper(II) schiff base complex with a bridging m-phenylenediamine ligand(De Gruyter, 2005) Zeyrek, C. Tuğrul; Elmalı, Ayhan; Elerman, Y.; Svoboda, I.; 0000-0001-6744-7841; TAEK-ANAEMCondensation of 2-hydroxy-3-methoxybenzaldehyde with m-phenylenediamine (1,3-diaminobenzene) (m-pda) gives the ligand [N,N′-bis(2-hydroxy-3-methoxybenzylidene)-1,3-diaminobenzene] which reacts with cupric acetate to give the complex [Cu2(L-m-pda)2]·2H2O, [L = 2-hydroxy-3- methoxybenzaldehyde)]. The molecular structure of the complex [Cu2(L-m-pda)2]·2H2O has been determined by single-crystal X-ray analysis. (C44H40Cu2N4O8)·2H2O, triclinic, space group P1̄. Two [Cu(L-m-pda)] fragments, related by an inversion center, are connected by m-phenylene groups to form a binuclear unit. The coordination geometry around each copper(II) can be described as a distorted tetrahedron formed by the N2O2 donor set of the Schiff base ligands. The intramolecular Cu···Cu separation is 7.401(6) Å. The magnetic susceptibility of the complex in the 5 - 301 K temperature range can be rationalized by the parameters J = −0.4 cm−1 and g = 2.17. This indicates a weak intramolecular antiferromagnetic interaction. Extended Hückel molecular orbital (EHMO) calculations have been performed in order to gain insight into the molecular orbitals that participate in the super-exchange pathway.Item Iron(III) induced imidazolidine ring hydrolysis of binucleating schiff base ligand: synthesis, crystal structures, spectroscopic properties and conformational study of a new μ-bis(tetradentate) schiff base and its mononuclear iron(III) complex(De Gruyter, 2005-05) Zeyrek, C. Tuğrul; Elmalı, Ayhan; Elerman, Y.; 0000-0001-6744-7841; TAEK-ANAEMThe μ-bis(tetradentate) ligand, [C27H26Cl3N4O4], H3L′, 1,3-bis[N-(5-chloro-2-hydroxybenzylidene)- 2-aminoethyl]-2-(5-chloro-2-hydroxyphenyl)imidazolidine and its mononuclear iron(III) complex, [Fe(L)](ClO4), L = N, N′-bis(5-chloro-2-hydroxybenzylidene)-triethylenetetramine have been synthesized and their crystal structures determined. Minimum energy conformations of the ligand were calculated (MOPAC, AM1) as a function of two torsion angles and the results compared with optimized crystal structure. The ligand (H3L′) reacts with Fe(ClO4)2 · 6H2O in aqueous methanol to form the mononuclear [Fe(L)](ClO4) complex with the imidazolidine ring cleaved by hydrolysis. The complex has an N4O2 donor atom set forming a distorted octahedral coordination geometry around the metal atom as established from a crystal structure determination. The terminal oxygen donor atoms occupy cis positions, and the remaining four nitrogen atoms (two cis amine and two trans imine) complete the coordination sphere.Item Magnetic characterization, synthesis and crystal structure of a heterodinuclear CuIIGdIII Schiff base complex bridged by the two phenolic oxygen atoms(Elsevier, 2005-04) Zeyrek, C. Tuğrul; Elmalı, Ayhan; Elerman, Y.; 0000-0001-6744-7841; TAEK-ANAEMA novel heterodinuclear complex formed by the reaction of gadolinium nitrate with Schiff base complex of copper(II) has been synthesized and characterized. Preparation, crystal structure and magnetic properties of the heterodinuclear complex, LCu(Me2CO)Gd(NO3)3, (L=(N,N′-bis(2,3-dihydroxybenzylidene)-1,3-diaminopropane) are reported. The complex is consisting of a deca-coordinated GdIII ion which is bridged to four coordinated CuII via both phenolate oxygen atoms of the L Schiff base ligand. The average Cu⋯Gd separation is 3.475(2) Å. There is also one non-coordinating acetone molecule in the crystal structure. The magnetic susceptibility of the complex was measured over the range 4.5–350 K and the observed data were successfully simulated by the equation based on the spin-Hamiltonian operator H=−JSCu·SGd. The values of the intrachain interaction parameters have been deduced from the magnetic data: exchange integral J(Cu–Gd)=7.3 cm−1, gCu=2.17, gGd=2.09. This indicates a weak ferromagnetic spin exchange interaction between CuII and GdIII ions. The nature of the magnetic super-exchange interaction of the title compound is compared with similar CuIIGdIII heterodinuclear complexes.Item The synthesis, crystal structure and spectroscopic properties of a dinuclear μ–pyrazolato–N,N’–bridged dinickel(II) complex of 1,3-bis(salicylideneamino)propan–2–ol(De Gruyter, 2004) Zeyrek, C. Tuğrul; Elmalı, Ayhan; Elerman, Y.; 0000-0001-6744-7841; TAEK-ANAEMThe title compound [Ni2(L)(3,5 prz)], prz = pyrazolate with the formally pentadentate ligand L = 1,3-bis(salicylideneamino)propan-2-olate, was synthesized and identified using elemental analysis and IR spectroscopy. It crystallizes in the monoclinic space group P21/c with cell parameters a = 29.873(4), b = 11.131(2), c = 13.166(3) Å , β = 107.770(10)°, V = 4169.0(13) Å3, Z = 4, Dcal = 1.618 Mg/m3. The nickel ions are bridged by the alkoxo group of the ligand and the N atoms of the μ-pyrazolate group. Each nickel(II) ion is coordinated by two N atoms and two O atoms, forming a square with trans-N2O2 geometry. The Ni···Ni distance and the Ni−O−Ni angle are 3.371(1) Å and 126.4(1)°, respectively.