Celal Tuğrul Zeyrek

Conformational study and structure of N-(2,5-methylphenyl)salicylaldimine

Abstract N-(2,5-methylphenyl)salicylaldimine (C15H15NO) has been investigated by X-ray analysis and AM1 semi-empirical quantum mechanical method. The crystal is in the orthorhombic space group P212121 with a = 6.839(1), b = 7.720(4), c = 23.183(3) A , V = 1224.1(2) A 3 , Z = 4, Dc = 1.222 g cm−3 and μ(Mo Kα) = 0.076 mm−1. The title structure was solved by direct methods and refined to R = 0.0364 for 1489 reflections [I > 2σ(I)] by full-matrix anisotropic least-squares methods. The title compound is photochromic and the molecule is not planar. There is a strong intramolecular hydrogen bond of distance 2.604(2) A between the hydroxyl oxygen atom and imine nitrogen atom, the hydrogen atom essentially being bonded to the oxygen atom. Minimum energy conformations from AM1 were calculated as a function of three torsion angles, θ1 (C8N1C7C6), θ2 (C9C8N1C7) and θ3 (N1C7C6C5), varied every 10°. The optimized geometry of the crystal structure corresponding to non-planar conformation is the most stable conformation in all calculations. The results strongly indicate that the minimum energy conformation is primarily determined by non-bonded hydrogen-hydrogen repulsions.

Synthesis, structure, spectroscopic (FT-IR) and density functional modelling studies of 1-[(4-ethoxyphenylimino)methyl]napthalene-2-ol

Synthesis, crystallographic characterisation, spectroscopic (Fourier transform infrared spectroscopy [FT-IR]) and density functional modelling studies of the Schiff base 1-[(4-ethoxyphenylimino)methyl]napthalene-2-ol (C19H17NO2) have been reported. The molecular structure obtained from X-ray single-crystal analysis of the investigated compound in the ground state has been compared using Hartree–Fock and density functional theory (DFT) with the 6-311++G(d,p) basis set. In addition to the optimised geometrical structures, atomic charges, molecular electrostatic potential, natural bond orbital, non-linear optical (NLO) effects and thermodynamic properties of the compound have been investigated by using DFT. The experimental (FT-IR) and calculated vibrational frequencies (using DFT) of the title compound have been compared. The solvent effect was also investigated for obtained molecular energies and the atomic charge distributions of the compound. There exists a good correlation between experimental and theoretical data for enol-imine form of the compound. The total molecular dipole moment (µ), linear polarisability (α), and the first-order hyperpolarisability (β) were predicted by the B3LYP method with different basis sets 6-31G(d), 6-31+G(d,p), 6-31++G(d,p), 6-311+G(d) 150 and 6-311++G(d,p) for investigating the effects of basis sets on the NLO properties. Our computational results yield that βtot for the title compound is greater than those of urea.

Structures of four- and six-coordinate monomers of [N,N′-bis(5-chlorosalicylidene)-1,3-diaminopropane]nickel(II)

Abstract[N,N′-Bis(5-chlorosalicylidene)-1,3-diaminopropane]nickel(II) [Ni(C17H14N2O2Cl2)] 1 and [N,N′-Bis(5-chlorosalicylidene)-1,3-diaminopropane]nickel(II) dihydrate [Ni(C17H14N2O2Cl2).2(H2O)] 2 were synthesized, and their crystal structures were determined. Compound 1 is monoclinic, space group C2/c, a = 21.063(4), b = 8.151(1), c = 9.421(2) Å,β = 94.16(1)°, V = 1613.2(5) Å3, Z = 4 and Dc = 1.680 g cm−3. Compound 1 contains a crystallographic twofold axis, and the whole molecule is not planar. The two Schiff base moieties, which in themselves are planar, are twisted with respect to one another. The least-squares planes through each half of the molecule are inclined at an angle of 29.1(1)°. The Ni atom is in a square-planar environment. The Ni—N and Ni—O distances are 1.958(2) and 1.910(2) Å, respectively. Compound 2 is orthorhombic, space group Pnma, witha = 7.892(1), b = 23.396(2), c = 9.992(1) Å, V = 1846.3(3) Å3, Z = 4 and Dc = 1.597 g cm−3. Compound 2 has crystallographic mirror symmetry, and again, the whole molecule is not planar. The two planar Schiff base moieties inclined at an angle of 38.7(1)°. The Ni atom is in a distorted octahedral geometry and coordinated by the donor atoms of the ligand in the horizontal plane, and the coordination sphere is completed by O atoms of two water molecules.

Synthesis and Crystal Structures of a New μ-Bis(tetradentate) Schiff Base Ligand and its Mononuclear Iron(III) Complex: Iron(III) Induced Imidazolidine Ring Hydrolysis of Binucleating Schiff Base Ligand

The 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.

Crystal structure and magnetic exchange interaction in a binuclear copper(II) Schiff base complex with a bridging m-phenylenediamine ligand

Condensation 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.

Density functional modelling studies of chloride-substituted Schiff bases as corrosion inhibitors: Optimized geometries, atomic charges, solvent and non-linear optical effects

The anti-corrosive properties, optimized geometrical structures, atomic charges, molecular electrostatic potential (MEP) surfaces and non-linear optical (NLO) effects of some chloride-substituted Schiff bases salicylaldimine (R), N-(2-chlorophenyl)salicyaldimine (2Cl–R), N-(3-chlorophenyl)salicyaldimine (3Cl–R) and N-(4-chlorophenyl)salicyaldimine (4Cl–R) have been investigated by using density functional modelling calculations. The quantum chemical parameters, such as the highest occupied molecular orbital, the lowest unoccupied molecular orbital, gap energy and other parameters, including electronegativity, global hardness, the total charges on the whole molecules and the total energies have been calculated and discussed to obtain information about the relationships between the molecular and electronic structures of the studied inhibitors and their experimental corrosion inhibition efficiencies. The linear polarizability (α), and the firstorder hyperpolarizability (β) have been also predicted by the density functional theory (DFT) with different base sets 6-31G(d), 6-31+G(d,p), 6-31++G(d,p), 6-311+G(d) and 6-311++G(d,p) for investigating the effects of basis sets on the NLO properties.

Synthesis, characterization, and evaluation of (E)-methyl 2-((2-oxonaphthalen-1(2H)-ylidene)methylamino)acetate as a biological agent and an anion sensor

An amino acid based and bidentate Schiff base, (E)-methyl 2-((2-oxonaphthalen-1(2H)-ylidene)methylamino)acetate (ligand), was synthesized from the reaction of glycine-methyl ester hydrochloride with 2-hydroxy-1-naphthaldehyde. Characterization of the ligand was carried out using theoretical quantum-mechanical calculations and experimental spectroscopic methods. The molecular structure of the compound was confirmed using X-ray single-crystal data, NMR, FTIR and UV-Visible spectroscopy, which were in good agreement with the structure predicted by the theoretical calculations using density functional theory (DFT). Antimicrobial activity of the ligand was investigated for its minimum inhibitory concentration (MIC) to several bacteria and yeast cultures. UV-Visible spectroscopy studies also shown that the ligand can bind calf thymus DNA (CT-DNA) electrostatic binding. In addition, DNA cleavage study showed that the ligand cleaved DNA without the need for external agents. Energetically most favorable docked structures were obtained from the rigid molecular docking of the compound with DNA. The compound binds at the active site of the DNA proteins by weak non-covalent interactions. The colorimetric response of the ligand in DMSO to the addition of equivalent amount of anions (F-, Br-, I-, CN-, SCN-, ClO4-, HSO4-, AcO-, H2PO4-, N3- and OH-) was investigated and the ligand was shown to be sensitive to CN- anion.

Crystal Structure and Magnetic Properties of a Dinuclear Iron(III) Doubly Oxygen Bridged Schiff Base Complex

[Fe(L)Cl]2 (L = N-(4-methylphenyl)-3-methoxy-salicylaldimimine) was synthesized and its crystal structure determined. [C30H26Cl2Fe2N2O6], triclinic, space group P 1̄ , a = 9.278(2), b = 9.4050(10), c = 10.489(2) Å , α = 64.43(2), β = 74.540(10), γ = 62.40(2)° , V = 729.1(2) Å 3, Z = 1. Two identical [Fe(L)Cl] fragments, related by an inversion center, are connected by two bridging O atoms to form a binuclear unit. The iron(III) centers are separated by 3.196(2) Å and weakly antiferromagnetically coupled (J = -10.1(1) cm-1), as derived from temperature-dependent magnetic susceptibility measurements in the range 5.1-283.5 K.

Experimental, DFT Calculation, Biological Activity, Anion Sensing Application Studies and Crystal Structure of ( E )-4-[(pyridin-3-ylimino)methyl]benzene-1,3-diol

AbstractCrystallographic and spectroscopic studies of (E)-4-[(pyridin-3-ylimino)methyl]benzene-1,3-diol have been performed. Optimized molecular structure, conformational analysis, theoretical vibrational band assignments, nonlinear optical effects, UV–Vis, properties have also been investigated by using density functional theory with the functional B3LYP using the 6-311++G(d,p) basis set. The antimicrobial activities of the compound were investigated for its minimum inhibitory concentration. The colorimetric response of the Schiff base receptors was investigated before and after the addition of an equivalent amount of each anion to evaluate anion recognition properties.Graphical AbstractA new Schiff base was prepared and characterized. Experimental and theoretical studies on a new Schiff base have been reported. The tautomeric stability of the compound was investigated by experimental and theoretical (DFT). The nonlinear optical (NLO) effects of the compound was predicted using DFT. The antimicrobial activity and anion-sensor properties of the compound were examined.

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

Abstract The 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.