Muhittin Aygün

Aromaticity balance, π-electron cooperativity and H-bonding properties in tautomerism of salicylideneaniline: the quantum theory of atoms in molecules (QTAIM) approach.

Topological analysis based on DFT calculations regarding proton transfer reaction in salicylideneaniline (SA) was performed to scrutinize possible changes in the intramolecular H-bond, π-electron delocalization and aromaticity levels of certain fragments. Quantum chemical calculations and natural bond orbital (NBO) analyses were carried out over a tautomeric ensemble whose members correspond to the molecules at different stages in tautomeric interconversion of SA. The elaboration of intramolecular hydrogen bonding in terms of the relevant topological parameters and the interpretation of certain dependencies regarding its strength were examined. The results show that delocalization index (DI) between donor and acceptor atom δ(O,N) is a useful topological parameter for describing H-bond strength, which is influenced by π-delocalization level within quasiaromatic chelate ring, indicating its resonance-assisted character. NBO analyses reveal that lone-pair (LP) population on N center also affects the strength of intramolecular H-bond in SA. Furthermore, π-electron transfer accompanying intramolecular proton migration in SA is brought into being through formally vacant non-Lewis type LP* orbital on the tautomeric proton. As a result of this, tautomeric protons in molecular entities near TS have hypovalent character due to the lack of electron population in the bonding orbital relative to that in LP* orbital. While H-bonds in the tautomeric ensemble of SA are predominantly partial covalent, molecular entities close to transition state have the strongest covalent H-bonds. The most important result is also that there are linear correlations between the orders of bonds (hydroxyl and amine) involving intramolecular H-bond and electron density values at the relevant BCPs due to partially covalent character of these bonds, contrary to exponential behavior as for purely covalent bonds. Quasiaromatic chelate ring formation is established not only to compel a reduced aromaticity of salicylidene ring but also to decrease in LP-population on N.

1-((E)-{(1R,2R)-2-[(E)-(2-Hydr­oxy-1-naphth­yl)methyl­eneamino]cyclo­hexyl}iminiometh­yl)naphthalen-2-olate: a Schiff base compound having both OH and NH character

The title Schiff base compound, C(28)H(26)N(2)O(2), possesses both OH and NH tautomeric character in its molecular structure. While the OH side of the compound is described as an intermediate state, its NH side adopts a predominantly zwitterionic form. The molecular structure of the compound is stabilized by both N(+)-H...O(-) and O-H...N intramolecular hydrogen bonds. There are two weak C-H...O hydrogen bonds leading to polymeric chains of topology C(5) and C(13) running along the b axis of the unit cell. In addition, intermolecular C-H...pi interactions serve to stabilize the extended structure.

The synthesis, electrochemical properties and structural characterization of bis(N-(4-dimethylaminophenyl)-3,5-di-tert- butylsalicylaldiminato)copper(II)

A Cu(II) complex of a Schiff base obtained by the condensation of N,N-dimethyl-1,4-phenylenediamine with 3,5-di-tert-butyl-2-hydroxybenzaldehyde has been synthesized and characterized. The structure of the complex was determined by single-crystal X-ray methods. The four-coordinate Cu(II) ion possesses a compressed tetrahedral coordination environment.

2-[(4-Hydroxyphenyl)iminomethyl]-thiophene

The molecular structure of the title compound, C(11)H(9)NOS, has three planar moieties, two of which are rings, namely the hydroxyphenyl and the thiophene, with an angle of 20.76 (10) degrees between them. The crystal structure is stabilized by an O-H.N hydrogen bond and by C-H.O intermolecular interactions. The C.O intermolecular contact distance is 3.443 (2) A.

The synthesis and structural characterization of a N -heterocyclic carbene-substituted palladacycle

Reaction of {[Pd(dmba)(μ-Cl)]2} (dmba = (CH3)2NCH2C6H4) with an in situ generated N-heterocyclic carbene (NHC = 1,3-dimesitylimidazolidin-2-ylidene) afforded crystals containing [chloro-(1,3-dimesitylimidazolidin-2-ylidene)(N,N-dimethylaminobenzyl-C1,N)palladium(II)] (VII). Molecular and crystal structures of the title compound have been determined by single crystal X-ray diffraction technique. Complex VII crystallizes in space group P 1, with a = 13.685(3) Å, b = 13.590(2) Å, c = 16.229(3) Å, α = 87.162(13)°, β = 70.514(15)°, γ = 84.153(16)°, Z = 4, D Calcd = 1.367 g cm−3. There are two independent molecules in the asymmetric unit.

Crystal structure and photoluminescence properties of a new Cd(II) coordination polymer catena-poly[bis[4-bromo-2-({[2-(pyrrolidin-1-yl)ethyl]imino}methyl)phenolato-κ(3)N,N',O]di-μ3-chlorido-di-μ2-chlorido-bis(methanol-κO)tricadmium(II)].

Schiff base-metal complexes have been used widely as catalysts for many organic reactions, such as ring-opening polymerization and oxidation. In view of the importance of Cd(II) coordination polymers and in an effort to enlarge the library of such complexes, the title novel polymeric Cd(II) tridentate Schiff base complex, [Cd3(C13H16BrN2O)2Cl4(CH4O)2]n, has been synthesized and characterized by elemental analyses, UV and IR spectroscopies, and single-crystal X-ray diffraction. The complex crystallizes in the triclinic P-1 space group with two symmetry-independent Cd(II) atoms, one of which lies on an inversion centre, and analysis of the crystal structure shows that both Cd(II) atoms are six-coordinated; the environment around one Cd(II) atom can be described as distorted octahedral, while that around the second Cd(II) atom is octahedral. The Cd(II) atoms are linked by chloride ligands to form a one-dimensional coordination polymer. The nonbonding intermolecular Cd...Cd distances are 3.7009 (4) and 4.3563 (5) Å. Furthermore, the photoluminescence properties of the complex have been investigated and it displays a strong red emission in the solid state at room temperature.

Synthesis, structures, DNA/protein binding, molecular docking, anticancer activity and ROS generation of Ni(II), Cu(II) and Zn(II) 5,5-diethylbarbiturate complexes with bis(2-pyridylmethyl)amine and terpyridine

A series of structurally related Ni(II), Cu(II) and Zn(II) 5,5-diethylbarbiturate (barb) complexes with bis(2-pyridylmethyl)amine (1–3) and terpyridine (4–6) were synthesized and characterized using elemental analysis, UV-vis, IR, and ESI-MS. Single-crystal X-ray diffraction analysis showed that all complexes are mononuclear. Interactions of the complexes with DNA and protein were studied in detail using experimental and molecular docking techniques, indicating that all the complexes bind to DNA, exhibiting non-covalent binding specificity for G/C and A/T rich regions via a partial intercalative/groove binding mode, and effectively quench the intrinsic fluorescence of BSA through intermolecular interactions. The Cu(II) complexes (2 and 5) displayed a moderate antioxidant activity. In vitro cytotoxicity of 1–6 towards four cancer cell lines was evaluated and compared with that of cisplatin. 2 and 5 showed potent and selective cytotoxic activity against MCF-7 cells, suggesting that the DNA/BSA binding affinity of both complexes correlates with their growth inhibition effects. Furthermore, both complexes induced apoptosis on MCF-7 cells as revealed using flow cytometry analysis. The cytotoxicity and apoptosis induction exerted by 2 and 5 were associated with production of reactive oxygen species (ROS).

Magnetic properties and sensitized visible and NIR luminescence of DyIII and EuIII coordination polymers by energy transfer antenna ligands

ABSTRACT Two coordination polymers, {[Ln(2-stp)(4,4′-bipy)(H2O)].(H2O)}, [Ln = Dy (1) and Eu (2), 2-stp = 2-sulfoterephthalate and 4,4′-bipy = 4,4′-bipyridine] have been characterized by solid state UV-vis, FTIR spectra, X-ray single crystal diffraction and solid state photoluminescence. Variable-temperature magnetic susceptibility and isothermal magnetization as function of external magnetic field is also studied for both complexes. After ligand-mediated excitation, both complexes show the characteristic visible and NIR luminescence of the corresponding LnIII ions (Ln = Dy, Eu) which is due to efficient energy transfer from the ligands to the central LnIII ions via an antenna effect. The indirect energy transfer in both complexes has been investigated and discussed in detail.

Synthesis, Characterization and Crystal Structure of New 2-Morpholinoethyl-Substituted Bis-(NHC)Pd(II) Complexes and the Catalytic Activity in the Direct Arylation Reaction

This paper contains the synthesis of the new 2-morpholinoethyl substituted bis-(NHC)Pd(II) complexes and their catalytic activity in direct arylation reaction. The new bis-(NHC)Pd(II) complexes have been prepared from Ag(I)NHC complexes by using transmetallation method. The new bis-(NHC)Pd(II) complexes have been characterized by using 1H NMR, 13C NMR, FTIR spectroscopy and elemental analysis techniques. Molecular and crystal structure of the complex 1a and its ligand (N-benzylbenzimidazole) were obtained by single crystal X-ray diffraction method. The new bis-(NHC)Pd(II) complexes exhibit activity in the reaction after being examined as catalysts in the direct arylation (C–H activation) reaction.Graphical Abstract

Crystal structure and photoluminescence properties of a new monomeric copper(II) complex: bis­(3-{[(3-hy­droxy­prop­yl)imino]­meth­yl}-4-nitro­phenolato-κ3O,N,O′)copper(II)

Copper(II)-Schiff base complexes have attracted extensive interest due to their structural, electronic, magnetic and luminescence properties. The title novel monomeric CuII complex, [Cu(C10H11N2O4)2], has been synthesized by the reaction of 3-{[(3-hydroxypropyl)imino]methyl}-4-nitrophenol (H2L) and copper(II) acetate monohydrate in methanol, and was characterized by elemental analysis, UV and IR spectroscopies, single-crystal X-ray diffraction analysis and a photoluminescence study. The CuII atom is located on a centre of inversion and is coordinated by two imine N atoms, two phenoxy O atoms in a mutual trans disposition and two hydroxy O atoms in axial positions, forming an elongated octahedral geometry. In the crystal, intermolecular O-H...O hydrogen bonds link the molecules to form a one-dimensional chain structure and π-π contacts also connect the molecules to form a three-dimensional structure. The solid-state photoluminescence properties of the complex and free H2L have been investigated at room temperature in the visible region. When the complex and H2L are excited under UV light at 349 nm, the complex displays a strong green emission at 520 nm and H2L displays a blue emission at 480 nm.