Lenka Kucková

Synthesis, Crystal Structure, Spectroscopic Properties and Potential Biological Activities of Salicylate-Neocuproine Ternary Copper(II) Complexes

Mixed ligand copper(II) complexes containing derivatives of salicylic acid and heterocyclic ligands with nitrogen donor atoms have been the subject of various studies and reviews. In this paper, synthesis and characterization of the ternary copper(II) complexes of neocuproine (2,9-dimethyl-1,10-phenanthroline, Neo) and salicylate ligands (Sal) are reported. In addition, the crystal structures of ([Cu(H2O)(5-Cl-Sal)(Neo)] (1), [Cu(μ-Sal)(Neo)]2 (2), Cu2(μ-5-Cl-Sal)(5-Cl-HSal)2(Neo)2]·EtOH (3)) were determined. In order to compare structural and biological properties of the prepared complexes, spectroscopic and biological studies were performed. Results of X-ray diffraction show that prepared complexes form three types of crystal structures in a given system: monomeric, dimeric and dinuclear complex. The preliminary study on the DNA cleavage activity has shown that the complexes under study behave as the chemical nucleases in the presence of added hydrogen peroxide with slight differences in the activity (1 > 2 > 3). The complexes 1 and 2 exhibited nuclease activity itself indicating the interaction of complexes with the DNA. It has been proposed that the enhanced destructive effect of the complexes 1 and 2 on the DNA is a result of two possible mechanisms of action: (i) the conversion of closed circular DNA (form I) to the nicked DNA (form II) caused by the copper complex itself and (ii) damage of DNA by Reactive Oxygen Species (ROS)—products of the interaction of copper with hydrogen peroxide by means of Fenton reaction (hydroxyl radicals). Thus the biological activity of the prepared Cu(II) complexes containing derivatives of salicylic acid and phenanthroline molecules is substantiated by two independent mechanisms. While derivatives of salicylic acids in the coordination sphere of copper complexes are responsible for radical-scavenging activity (predominantly towards superoxide radical anion), the presence of chelating ligand 2,9-dimethyl-1,10-phenanthroline significantly enhances capability of Cu(II) complexes binding to DNA via intercalation.

Conformational, spectroscopic, and molecular dynamics DFT study of precursors for new potential antibacterial fluoroquinolone drugs.

Biological activity, functionality, and synthesis of (fluoro)quinolones is closely related to their precursors (for instance 3-fluoroanilinoethylene derivatives) (i.e., their functional groups, conformational behavior, and/or electronic structure). Herein, the theoretical study of 3-fluoroanilinoethylene derivatives is presented. Impact of substituents (acetyl, methyl ester, and ethyl ester) on the conformational analysis and the spectral behavior is investigated. The B3LYP/6-311++G** computational protocol is utilized. It is found that the intramolecular hydrogen bond N-H···O is responsible for the energetic preference of anti (a) conformer (anti position of 3-fluoroanilino group with respect to the C═C double bond). The Boltzmann ratios of the conformers are related to the differences of the particular dipole moments and/or their dependence on the solvent polarity. The studied acetyl, ethyl ester, and methyl ester substituted fluoroquinolone precursors prefer in the solvent either EZa, ZZa, or both conformers equally, respectively. In order to understand the degree of freedom of rotation of the trans ethyl ester group, B3LYP/6-311G** molecular dynamic simulations were carried out. Vibrational frequencies, electron transitions, as well as NMR spectra are analyzed with respect to conformational analysis, including the effect of the substituent. X-ray structures of the precursors are presented and compared with the results of the conformational analysis.

4-Chloro-N-phenyl-benzamide.

In the title compound, C13H10ClNO, the dihedral angle between the two benzene rings is 59.6 (1)°. The crystal structure features N—H⋯O hydrogen bonds, which link the molecules into C(4) chains running along the a axis.

Charge density study of bis(clonixato)bis(ethanol) bis(imidazole)copper(II) complex

Abstract An experimental electronic structure of bis(clonixato)bis(ethanol) bis(imidazole)copper(II) complex, [Cu(cln)2(im)2(EtOH)2] (cln=clonixato, im=imidazole) (1) has been obtained from single-crystal X-ray diffraction data collected at 100 K using an Incoatec IμS Ag microfocus source. Metal-ligand (ML) bonds and hydrogen bonds (HBs) have been analysed using topological analysis of the experimental electron density with the atoms in molecules (AIM) approach. The central copper atom is octahedrally coordinated by two oxygen atoms from two clonixato anions and two nitrogen atoms from two imidazole ligands in equatorial plane. In axial positions are two oxygen atoms from two ethanol molecules. AIM analysis establishes that the central copper atom is bonded more strongly to the clonixato anion that to the imidazole or ethanol molecules. AIM analysis of two intramolecular and one intermolecular hydrogen bonds permits to estimate their strength. We show that the hydrogen bonds are strong enough to protect the molecule from decomposition in solvent media and to disable the more reactive imidazole-Cu-clonixato complex from interacting with e.g. a macromolecule. The electrostatic potential of the complex shows a highly positive value on the central atom, so the complex is highly reactive in an interaction with negative ligands.

Copper oxalate complexes: synthesis and structural characterisation

Six copper(II) oxalate complexes, namely {K2[Cu(ox)2]}n (1), {(Hiz)2[Cu(ox)2]}n (2), {[Cu(ox) (N-Bzliz)2]}n (3), (HMeiz)2[Cu(ox)2] (4), {[Cu(ox)(Meiz)2]}n (5), and [Cu(Hox)2(H2O)2](N-Bzliz) (6) where ox = oxalate ion, iz = imidazole, N-Bzliz = N-benzylimidazole, Meiz = 2-methylimidazole, were synthesised and characterised by single crystal X-ray diffraction (complexes 1–5) or powder X-ray diffraction (compound 6). The three-dimensional crystal packing structures of 2, 4, and 5 are consolidated by intermolecular hydrogen bonds linking the oxygen atom of the oxalate group and the amine or imine group of the imidazole-based part into chains. The molecules of complex 6 are held together by intermolecular hydrogen bonds between the oxygen atoms of the oxalate group and coordinated water molecules.

Application of oxone immobilized on montmorillonite for an efficient oxidation of mannose thioglycoside

A new solid system based on montmorillonite supported oxone has been developed and used for the oxidation of thiomannoside. The oxidation properties of oxone immobilized on montmorillonite were affected by polarity of the solvent, resulting in the different sulfoxide to sulfone ratios as the products. Toluene was the only solvent favouring sulfone formation over sulfoxide. X-ray crystal structures of the starting compound as well as the corresponding sulfoxide (major epimer Rs) and sulfone are also reported.Graphical Abstract

N-(3-Chloro-phen-yl)-4-methyl-benzamide hemihydrate.

In the title compound, C14H12ClNO·0.5H2O, the water molecule is located on a twofold axis of symmetry. The meta-Cl atom in the aniline ring is positioned anti to the N—H bond. The two benzene rings make a dihedral angle of 40.40 (11)°. The crystal structure is stabilized by intermolecular N—H⋯O and O—H⋯O hydrogen bonds, which link the molecules into chains along the a axis.

2-Chloro-N-(3-methylphenyl)benzamide

In the title compound, C14H12ClNO, the meta-methyl substituent in the aniline ring is positioned anti to the N—H bond. The dihedral angle between the rings is 12.4 (1)°. The crystal structure is stabilized by intermolecular N—H⋯O hydrogen bonds, which link the molecules into C(4) chains running along the c-axis direction.