A series of Schiff base ligands obtained by the condensation of trans-cyclohexane-1,2-diamine and fluorinated benzaldehydes were prepared, followed by their reduction with NaBH4. The reduced ligands were employed in the synthesis of zinc complexes of the general formula [ZnCl2(L)]. The structures of both the original and the reduced Schiff bases, as well as of the zinc complexes, were characterized by single-crystal X-ray analysis, along with NMR and IR spectroscopy. The antimicrobial activities of the reduced Schiff bases and their zinc complexes were evaluated in vitro against E. coli, S. aureus, and C. albicans. The compounds containing the 4-(trifluoromethylphenyl) moiety showed marked antibacterial activity. Interestingly, the antimicrobial effect of the zinc complex with this moiety was significantly higher than that of the corresponding free reduced ligand, comparable with ciprofloxacin used as standard. Thus, a synergic effect upon the complexation with zinc can be inferred.

An extensive characterization of [Ti(C 22 H 18 N 2 O 6 )]·H 2 O was performed by topological analysis according to Bader's quantum theory of atoms in molecules (QTAIM) from the experimentally (multipole model) and theoretically (DFT) determined electron density. To the best of our knowledge, this study is the first example of an experimental electronic structure of a coordination compound in which a peroxo anion is bonded to a 3 d central atom. The titanium coordination polyhedron could be described as a deformed tetrahedral pyramid if the midpoint of the peroxide O—O bond ( side-on mode) is considered to be in the quasi-apical position. According to the multipole model ( MM ) results, the titanium atom has a positive QTAIM charge of 2.05 e − which does not correspond to the formal Ti (IV) oxidation state. On the other hand, the peroxo oxygen atoms O(1) and O(2) have MM QTAIM charges of −0.27 and −0.12, respectively. This asymmetric charge density distribution on the peroxo oxygens is in agreement with the distorted orientation of the O 2 moiety with respect to the titanium atom. Despite the fact that the overall MM charge of the O 2 moiety is more remote from the formal −2 charge than from neutral O 2 , the O—O distance remains close to that in the peroxo O 2 2− anion. In the case of DFT results, the titanium atom charge is also found to be close to +2, the O 2 x − moiety charge is around −1, the optimized O—O distance is shorter by only ca 0.04 Å than the experimental value of 1.5005 (16) Å, and the DFT d -populations on titanium are found to be lower than the experimental MM value. This study is the first experimental electronic structure of a transition metal peroxo complex.

Metallodrugs form a large family of therapeutic agents against cancer, among which is cisplatin, a paradigmatic member. Therapeutic resistance and undesired side effects to Pt(II) related drugs, prompts research on different metal–ligand combinations with potentially enhanced biological activity. We present the synthesis and biological tests of novel palladium(II) complexes containing bisdemethoxycurcumin (BDMC) 1 and 2. Complexes were fully characterized and their structures were determined by X-ray diffraction. Their biological activity was assessed for several selected human tumor cell lines: Jurkat (human leukaemic T-cell lymphoma), HCT-116 (human colorectal carcinoma), HeLa (human cervix epitheloid carcinoma), MCF-7 (human breast adenocarcinoma), MDA-MB-231 (human mammary gland adenocarcinoma), A549 (human alveolar adenocarcinoma), Caco-2 (human colorectal carcinoma), and for non-cancerous 3T3 cells (murine fibroblasts). The cytotoxicity of 1 is comparable to that of cisplatin, and superior to that of 2 in all cell lines. It is a correlation between IC50 values of 1 and 2 in the eight studied cell types, promising a potential use as anti-proliferative drugs. Moreover, for Jurkat cell line, complexes 1 and 2, show an enhanced activity. DFT and docking calculations on the NF-κB protein, Human Serum Albumin (HSA), and DNA were performed for 1 and 2 to correlate with their biological activities.

Three novel transition metal complexes with selenadiazoloquinolones as potential broad spectrum antibiotics in clinical praxis.

The structure of 4-methyl-3-[(tetrahydro-2H-pyran-2-yl)oxy]thiazole-2(3H)-thione (MTTOTHP) was investigated using X-ray diffraction and computational chemistry methods for determining properties of the nitrogen-oxygen bond, which is the least stable entity upon photochemical excitation. Experimentally measured structure factors have been used to determine and characterize charge density via the multipole model (MM) and the maximum entropy method (MEM). Theoretical investigation of the electron density and the electronic structure has been performed in the finite basis set density functional theory (DFT) framework. Quantum Theory of Atoms In Molecules (QTAIM), deformation densities and Laplacians maps have been used to compare theoretical and experimental results. MM experimental results and predictions from theory differ with respect to the sign and/or magnitude of the Laplacian at the N-O bond critical point (BCP), depending on the treatment of n values of the MM radial functions. Such Laplacian differences in the N-O bond case are discussed with respect to a lack of flexibility in the MM radial functions also reported by Rykounov et al. [Acta Cryst. (2011), B67, 425-436]. BCP Hessian eigenvalues show qualitatively matching results between MM and DFT. In addition, the theoretical analysis used domain-averaged fermi holes (DAFH), natural bond orbital (NBO) analysis and localized (LOC) orbitals to characterize the N-O bond as a single σ bond with marginal π character. Hirshfeld atom refinement (HAR) has been employed to compare to the MM refinement results and/or neutron dataset C-H bond lengths and to crystal or single molecule geometry optimizations, including considerations of anisotropy of H atoms. Our findings help to understand properties of molecules like MTTOTHP as progenitors of free oxygen radicals.

Four new Cu(II) complexes and one Zn(II) complex of the formula {Cu(salChx)}2n⋅nCH3OH, [Cu(salChx)(imidazole)], [Cu(salChx)(pyrazole)], [Zn2(μ-salChx)2(CH3OH)2]and[Cu2(μ-MeOsalChx)(MeOsalChx)(H2O)2]4⋅3H2O (where salChx is dianion of Schiff-base ligand obtained by condensation of salicylaldehyde with1-aminocyclohexane-1-carboxylic acid and MeOsalChx isdianion of Schiff-base ligand obtained by condensation of 3-methoxysalicylaldehyde with1-aminocyclohexane-1-carboxylic acid) have been synthesized and crystallographically fully characterised. Four different geometrical isomers[Cu2(μ-MeOsalChx)(MeOsalChx)(H2O)2]constitute the latest coordination compound together withthree crystalline water molecules. They represent a new type of geometrical isomerism in coordination chemistry. Antimicrobial and antiradical activities of all five complexes were assayed.

An entry from the Cambridge Structural Database, the world’s repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.

An unexpected generation of a 5,7-bicyclic framework from 5-aminopyrazoles and 2,5-dimethoxytetrahydrofuran was detected in the synthesis of originally desired 5-pyrrol-1-ylpyrazoles. To gain insight about the structure and behavior of the novel studied compounds, heteronuclear 2D NMR (including 1H15N, 19F13C and 19F15N correlations), single-crystal X-Ray diffraction structural analysis and HR-MS were exploited. Four other syntheses were designed to obtain the pyrazoloazepines by independent reaction pathways which never yielded the desired bicyclic products obtained before. The reaction conditions of the original Clauson-Kaas synthesis were optimized to yield the pyrazoloazepines in reasonable yields.

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.

Altering the solid-state photochromic behavior of N-salicylideneanilines molecular switches by

The experimental electron density distribution in two isostructural and isomorphous complexes, tetrakis(μ2-acetato)diaquadicopper(II) [H2OCu(ac)2Cu(ac)2H2O] (I) and tetrakis(μ2-acetato)diaquadichromium(II), [H2OCr(ac)2Cr(ac)2H2O] (II), has been obtained from high-resolution X-ray diffraction data in order to shed light on the bonding properties in the compounds studied. It has been shown that from accurate X-ray data it is possible to discuss the bonding capability of the metal atom (Cu/Cr) and the ligands in these complexes. A comparison of results obtained from averaged and non-averaged X-ray data demonstrates that using the non-averaged data and introducing an anisotropic correction for secondary extinction errors provides a more detailed distribution of the electron density in the area of the metal atoms. In both complexes studied, the bonding of the acetate oxygen atom to the central metal atom is significantly affected by the formation of hydrogen bonds. The electron density and its Laplacian at the bond critical point of metal–oxygen coordination bonds for those oxygen atoms not involved in the intermolecular hydrogen bonds are approximately 10% larger compared with the case when oxygen atoms take part in hydrogen bonds with the neighboring water molecules. It is shown that metal–oxygen bonds in a quasi-equatorial plane are typical coordination bonds and differ significantly from the apical metal–oxygen bond. Metal–metal interaction with a small positive value of the electron density Laplacian at this bond critical point is mainly of electrostatic character. The metal–metal interaction is definitely not a bond according to the classical definition. Based on a search of the Cambridge Structural Database, it can be argued that there are four typical coordination bonds in the [CuO6] chromophore, similar to the four Cu—O coordination bonds in the basal plane of the CuO5 pyramid in one of the complexes under study.

Oxidative stress is the cause of many diseases and at the heart of it is the overproduction of reactive oxygen species (ROS). There are several protective enzymes, e.g., superoxide dismutases (SOD), able to decrease the level of ROS in the cell; however, a therapeutic use of these enzymes is problematic. Small molecule compounds and complexes able to scavenge free radicals such as superoxide anion radicals could be used instead. These compounds are often called SOD-mimics and various researches are interested in synthesis and study of these compounds. In our study, a series of Cu(II) complexes were synthesized, containing reduced Schiff base ligands prepared from salicylaldehyde and amino acids with longer chain length (5-aminopentanoic acid, 6-aminohexanoic acid, 8-aminooctanoic acid, 11-aminoundecanoic acid, and 12-aminododecanoic acid). Complexes prepared from these ligands are novel and were prepared using three different methods. An assay based on the ability to inhibit reduction of iodonitrotetrazolium dye by superoxide anion radicals was used to determine antiradical activity of the prepared complex. Most of the prepared complexes proved to be good antiradical agents compared to cystamine and the copper(II) complex with Schiff base type ligand N-salicylidene-β-alanine. The best IC50 values of the radical transfer of the prepared compounds were two complexes of N-(2-hydroxybenzyl)-11-aminoundecanoic acid: 97.0 ± 1.9 and 45.1 ± 0.5 μM.

The conformers of push–pull 3-[(2,2-dimethylhydrazinyl)methylene]-pentane-2,4-dione (CH3)2NNHCHC(COCH3)2 (DMHMP) have been studied experimentally by NMR and vibrational spectroscopy and theoretically by ab initio calculations at MP2 and DFT B3LYP levels in various basis sets. The NMR spectra were obtained in chloroform and dimethylsulfoxide and the IR and Raman spectra of DMHMP as a solid and as a solute in various less and more polar solvents at room temperature have been recorded.DMHMP was prepared as a pure solid and the data from X-ray analysis revealed that DMHMP exists in solid state as EZa conformer with an intramolecular hydrogen bond. The geometries and relative energies of possible conformers of DMHMP were evaluated at the both levels of theory in several basis sets and compared with the data from X-ray analysis.According to the NMR spectra the studied compound exists as a single entity. On the other hand vibrational spectra revealed that in less polar DMHMP solutions the presence of the second less polar ZZa conformer is possible, whereas in more polar solvent only one EZa conformer is observed. The influence of the environment polarity on this conformational equilibrium is discussed with respect to the SCRF solvent effect calculations using IEFPCM model. The observed IR and Raman bands were compared with calculated MP2/cc-pVTZ harmonic vibrational frequencies and assigned on the basis of potential energy distribution.

In studied compound of (CH3P(Ph)3)[Ni(bdtCl2)2], the methyl triphenylphosphonium bis (3,6-dichlorobenzene-1,2dithiolato) nickelate(1-) complex, the central atom coordination is square planar with nickel in oxidation state III [1].A new method was recently developed for the combined refinement of a unique electron density model, based on the data provided by three complementary techniques: X-ray diffraction (XRD), polarized neutron diffraction (PND) and neutron diffraction (ND) [2].Data collections for ND and PND were performed at 2 K on D19 and D3, respectively.X-ray diffractions experiments were performed by means of Stoe STADIVARI diffractometer equipped with a Dectris Pilatus 3R 300K and a Incoatec IμS Ag High Brilliance microfocus source (Ag-Kα, λ = 0.56083 Å) at 100 K using a nitrogen gas open-flow cooler Cobra Oxford Cryosystems.This method allows modeling both charge and spin densities from these three data sets and provides spin-resolved electron densities.Electronic structure and the results of AIM analysis together with the results of polarized neutron experiments will be discussed.

The convergent synthesis of broussonetinines related congeners 3 and 4 with the simple C13 alkyl side chain and differently configured pyrrolidine skeleton has been achieved. Our approach relied on the [3,3]-sigmatropic rearrangements of chiral allylic substrates derived from d-xylose. Cross metathesis of the common oxazolidinone intermediates 7 and 8 with tridec-1-ene followed by alkylative cyclization completed the construction of both C-alkyl iminosugars. The targeted compounds 3 and 4 were screened for antiproliferative/cytotoxic activities against multiple cancer cell lines by MTT assay. Compound 3 exhibited very good in vitro potency on Caco-2 and Jurkat cell lines with IC50 value of 5.1 μM and 5.8 μM, respectively.

In order to evaluate the influence of substitution on biological properties of Schiff bases and their metal complexes, a series of differently substituted fluorine-containing Schiff bases starting from the drug isoniazid (isonicotinylhydrazide) were prepared and their structures were established by single-crystal X-ray diffraction. Also, four copper(II) complexes of these Schiff bases were synthesized. The prepared compounds were evaluated for their antimicrobial activity and urease inhibition. Two of the Schiff bases exerted activity against C. albicans. All copper(II) complexes showed excellent inhibitory properties against jack bean urease, considerably better than that of the standard inhibitor acetohydroxamic acid.

Copper(II) complexes with fluoroquinolones in the presence of the nitrogen donor heterocyclic ligands 1,10-phenanthroline have been considered in detail. The phenanthroline moiety was introduced into the ligand environment with the aim to determine whether the nuclease activity is feasible. All suitable X-ray structures of the complexes under study reveal a distorted square pyramidal coordination geometry for Cu(II) atom. The conformational and spectroscopic (FT-IR and UV–visible) behavior has been analyzed and has been interpreted with respect to B3LYP/6-311G* calculations including molecular dynamics. The ability of the complexes to cleave DNA was studied by agarose gel electrophoresis with plasmid DNA pBSK+. The results have confirmed that the complexes under study behave as the chemical nucleases. Nuclease like activity in the absence of hydrogen peroxide allows us to deduce an interaction of the complexes with the DNA resulting in the conversion of supercoiled circular DNA to the nicked form. The DNA cleavage activity enhanced by the presence of hydrogen peroxide demonstrates the participation of reactive oxygen species, such as superoxide radical anions and hydroxyl radicals which presence was confirmed independently using the standard radical scavenging agents. It has been suggested that the radical formation through the Fenton/Haber–Weiss reaction is mediated by the redox cycling mechanisms with the participation of cupric/cuprous ions. Cytotoxic activity was evaluated as the 50% cytotoxic concentration (CC50). The potential effects of tested compounds on replication of murine gammaherpesvirus 68 (MHV-68) under in vitro conditions were also evaluated. However, no antiviral activity against MHV-68 was observed.