Hüseyin Ünver

Keto–enol tautomerism, conformations, and structure of 1-[N-(4-chlorophenyl)]aminomethylidene-2(1H)naphthalenone

Abstract1-[N-(4-chlorophenyl)]aminomethylidene-2(1H)naphthalenone (C17H12NOCl) (1) was synthesized and the crystal structure was determined. Compound 1 crystallizes in the monoclinic space group P21/n with a = 4.761(3) Å, b = 20.347(1) Å, c = 13.773(2) Å, β = 92.89(3)°, V = 1332.4(3) Å3, Z = 4, Dc = 1.404 g cm−3, μ(Mo Kα) = 0.28 mm−1, and R = 0.036 for 2680 reflections [I > 2σ(I)]. Molecule 1 is not planar, and the dihedral angle between the naphthaldeyde plane A [C1–C11, 01] and the 4-chloroaniline plane B [C12–C17, C11, N1] is 20.1(3)°. An intramolecular hydrogen bond occurs between the hydroxyl oxygen and imine nitrogen atoms [2.528(3) Å]. IR, 1H NMR, and UV measurements and AM1 semiempirical quantum mechanical calculations support the keto form found in the X-ray structure.

Intramolecular hydrogen bonding and tautomerism in N-(3-pyridil)-2-oxo-1-naphthylidenemethylamine

N-(3-pyridil)-2-oxo-1-naphthylidenemethylamine (C16H12N2O) was studied by elemental analysis, IR, 1H NMR, and UV–visible techniques and X-ray diffraction methods. The UV–visible spectrum of the compound was investigated in solutions effect polarity. The polarity of the some solvents was modifierly the additional (CF3COOH) and [(C2H5)3N]. The compound is in tautomeric equilibrium (phenol-imine O–H···N and keto-amine O···H–N forms) in polar and nonpolar solvents. The keto-amine form is observed in basic solutions of DMSO, ethanol, chloroform, benzene, cyclohexane, and in acidic solutions of chloroform and benzene, but not in acidic solutions of DMSO and ethanol. The compound crystallizes in the monoclinic, space group P21/a with a = 7.010(5) Å, b = 13.669(4) Å, c = 12.764(4) Å, β = 101.23(4)°, V = 1199.6(10) Å3, Z = 4, Dc = 1.375 g/cm3, μ(Mo Kα) = 0.088 mm−1, R = 0.045 for 1658 reflections [I > 2σ(I)]. The title compound is not planar two Schiff base moieties A [C1–C11, O1] and B [N1, C12, C13, N2, C14, C15, C16] are inclined at an angle of 27.4(1)° reflecting mainly the twist about C12–N1 [C11–C12–N1–C13, 29.7(2)°]. There is a strong intramolecular hydrogen bond (O–H···N) of 2.529(2) Å.

Synthesis, spectroscopic studies and structures of square-planar nickel(II) and copper(II) complexes derived from 2-{(Z)-[furan-2-ylmethyl]imino]methyl}-6-methoxyphenol.

Two new nickel(II) [Ni(L)(2)] and copper(II) [Cu(L)(2)] complexes have been synthesized with bidentate NO donor Schiff base ligand (2-{(Z)-[furan-2-ylmethyl]imino]methyl}-6-methoxyphenol) (HL) and both complexes Ni(L)(2) and Cu(L)(2) have been characterized by elemental analyses, IR, UV-vis, (1)H, (13)C NMR, mass spectroscopy and room temperature magnetic susceptibility measurement. The tautomeric equilibria (phenol-imine, O-H...N and keto-amine, O...H-N forms) have been systemetically studied by using UV-vis absorption spectra for the ligand HL. The UV-vis spectra of this ligand HL were recorded and commented in polar, non-polar, acidic and basic media. The crystal structures of these complexes have also been determined by using X-ray crystallographic techniques. The complexes Ni(L)(2) and Cu(L)(2) crystallize in the monoclinic space group P2(1)/n and P2(1)/c with unit cell parameters: a=10.4552(3)A and 12.1667(4)A, b=8.0121(3)A and 10.4792(3)A, c=13.9625(4)A and 129.6616(3)A, V=1155.22(6)A(3) and 1155.22(6)A(3), D(x)=1.493 and 1.476 g cm(-3) and Z=2 and 2, respectively. The crystal structures were solved by direct methods and refined by full-matrix least squares to a find R=0.0377 and 0.0336 of for 2340 and 2402 observed reflections, respectively.

Intramolecular hydrogen bonding and tautomerism in 1-[N-(4-bromophenyl)]aminomethylidene-2(1H) naphthalenone

Abstract1-[N-(4-bromophenyl)]aminomethylidene-2(1H)naphthalenone (C17H12NOBr) (1) was synthesized and its crystal structure was determined. Compound (1) is monoclinic, space group P21/n with a = 4.808(1) Å, b = 20.617(1) Å, c = 13.750(1) Å, β = 93.004(1)°, V = 1361.11(3) Å3, Z = 4, Dc = 1.592 g·cm−3, μ(Mo Kα) = 3.014 mm−1, R = 0.051 for 1013 reflections [I > 2σ(I)]. There is a strong intramolecular hydrogen bond of distance 2.544(2) Å between the hydroxyl oxygen atom and imine nitrogen atom, the hydrogen atom essentially being bonded to the nitrogen atom. The title molecule is not planar. X-ray crystal structure determination reveals the existence of the keto (or predominantly keto) tautomer in (1). Spectra of compound (1) were observed by IR and NMR, and UV–visible spectra of (1) were studied in different solvents and acidic media.

Spectroscopic study and structure of (E)-2-[(2-chlorobenzylimino)methyl]methoxyphenol.

(E)-2-[(2-chlorobenzylimino)methyl]methoxyphenol has been synthesized from the reaction of 2-hydroxy-3-methoxy-1-benzaldehyde(o-vanillin) with 2-chlorobenzylamine. The title compound has been characterized by using elemental analysis, FT-IR, (1)H NMR, (13)C NMR and UV-vis spectroscopic techniques. The crystal structure of the title compound has also been examined cyrstallographically. It crystallizes in the orthorhombic space group Pbca with unit cell parameters: a = 7.208(1) A, b = 13.726(2) A, c = 27.858(4) A, V = 2756.0(1) A(3), D(c) = 1.18 g cm(-3) and Z = 8. The crystal structure was solved by direct methods and refined by full-matrix least squares to a find R = 0.046 for 2773 observed reflections.

Good optical limiting performance of indium and gallium phthalocyanines in a solution and co-polymer host

The optical limiting characteristics of tetra- and octasubstituted gallium and indium phthalocyanine complexes have been studied by means of the open-aperture Z-scan technique with nanosecond pulses at 532 nm. The nonlinear response demonstrated that all investigated compounds exhibited strong reverse saturable absorption for both solution and solid-state-based experiments. The results showed that the ratio of the excited to ground state absorption cross section κ and effective nonlinear absorption coefficient βeff are largely dependent on the linear absorption coefficient. All compounds in chloroform exhibited almost the same optical limiting performance at the same linear absorption coefficient. Pc/PMMA composite films display a much larger effective nonlinear absorption coefficient, lower ratio of the excited to ground state absorption cross section and lower saturation fluence for optical limiting when compared to the same Pc molecules in solution. All gallium and indium complexes of phthalocyanines are good candidates for optical limiting applications.

SYNTHESIS AND SPECTROSCOPIC STUDIES IN SOME NEW SCHIFF BASES

Infrared, 1H-NMR and UV-visible spectra of a series of substituted 2-hydroxy-1-naphthaldehyde Schiff bases were used to investigate enol-imine and keto-amine tautomeric equilibrium. They were synthesised and studied by elemental analysis. From the IR spectra of the model compounds it was possible to assign the IR absorption for the C═O and the C═N groups in both the keto-amine and enol-imine forms. It was possible to assign other absorptions which were either specific to the keto-amine or the enol-imine forms. Specific pattern was observed for all the studied compounds. The UV-visible spectra of compounds have been investigated in different solvent, acidic and basic media. The compounds were in tautomeric equilibrium (enol-imine O─H ⃛N, keto-amine O ⃛H─N forms) in polar and non-polar solvents. The keto-amine form was observed in basic solutions of DMSO, ethanol, chloroform, benzene, cyclohexane and in acidic solutions of chloroform and benzene, but not in acidic solutions of DMSO and ethanol.

Third-order nonlinear optical properties and structures of (E)-N-(4-nitrobenzylidene)-2,6-dimethylaniline and (E)-N-(4-nitrobenzylidene)-2,3-dimethylaniline.

(E)-N-(4-Nitrobenzylidene)-2,6-dimethylaniline (1) and (E)-N-(4-nitrobenzylidene)-2,3-dimethylaniline (2) have been synthesized. The crystal structures of both compounds have been defined by X-ray diffraction analysis. The maximum one-photon absorption (OPA) wavelengths recorded by quantum mechanical computations using a configuration interaction (CI) method are estimated in the UV region to be shorter than 450nm, showing good optical transparency to the visible light. To provide an insight into the microscopic third-order nonlinear optical (NLO) properties of the investigated molecules, both dispersion-free (static) and also frequency-dependent (dynamic) linear polarizabilities (alpha) and second hyperpolarizabilities (gamma) at lambda=825-1125nm and 1050-1600nm wavelength areas have been computed using time-dependent Hartree-Fock (TDHF) method. According to the ab initio calculation results, the title molecules exhibit second hyperpolarizabilities with non-zero values, implying microscopic third-order NLO behavior.

THE INVESTIGATION OF ELECTRONIC PROPERTIES AND MICROSCOPIC SECOND-ORDER NONLINEAR OPTICAL BEHAVIOR OF 1-SALICYLIDENE-3-THIO-SEMICARBAZONE

To investigate the microscopic second-order nonlinear optical (NLO) behavior of the 1-salicylidene-3-thio-semicarbazone Schiff base compound, the electric dipole moments (μ), linear static polarizabilities (α) and first static hyperpolarizabilites (β) have been calculated using finite field second-order Moller-Plesset perturbation (FF MP2) theory. The ab-initio results on (hyper)polarizabilities show that the investigated molecule might have microscopic NLO properties with non-zero values. To understand the NLO behavior in the context of molecular orbital structure, we have also examined the highest occupied molecular orbital (HOMO), the lowest unoccupied molecular orbital (LUMO) and the HOMO-LUMO gap in the same theoretical framework as the (hyper)polarizability calculations. In addition to the NLO properties, the electronic transition spectra have been computed using a semi-empirical method (ZINDO). ZINDO calculation results show that the electronic transition wavelengths have been estimated to be shorter than 400 nm.

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.