Grzegorz Dutkiewicz

Crystal structure, electrochemistry, and catalytic studies of a series of new oxidovanadium(IV) Schiff-base complexes derived from 1,2-diphenyl-1,2-ethylenediamine

New derivatives of N2O2 tetradentate Schiff bases, from condensation of meso-1,2-diphenyl-1,2-ethylenediamine and salicylaldehyde derivatives (X-salicylaldehyde; X = 3-OMe, 4-OMe, 5-OMe, 6-OMe, 5-Cl, 5-Me), and oxidovanadium(IV) complexes were synthesized and characterized by 1H NMR, UV-Vis, IR spectroscopy, and elemental analysis. Crystal structure of 5-OMe; H2L3 and two of the complexes (VOL2 and VOL3) were also obtained. In the crystals, the molecule of H2L3 is Ci symmetrical, as it occupies the special position on the center of symmetry; its conformation is partially determined by classical intramolecular O–H···N hydrogen bonds. The complexes have monomeric structures with a distorted square pyramid of vanadium, with the oxo ligand in the apical position. Cyclic voltammetry studies show quasi-reversible VIV/VV redox for which the presence of electron-withdrawing groups on salicylaldehyde derivatives shifts the E° to more positive values. The complexes were used as catalysts for selective epoxidation of cyclooctene with tert-butylhydroperoxide as oxidant, in various solvents and reaction conditions. High catalytic activities and excellent selectivity was found. The catalytic activity of the complexes increased increasing E°, a consequence of the presence of electronegative substituents. This epoxidation process with the new catalysts was also studied under solvent-free condition and excellent reactivity was observed.

Topochemical bias in the hydrogen-bonded networks of guanidinium carboxybenzenesulfonates

Herein we describe the changes in the packing patterns and discuss the structural modifications in guanidinium carboxybenzenesulfonates G·CBS [C(NH2)3]+[XC6H4SO3]− (where X is the carboxylic group) compared with those in guanidinium benzenesulfonate G·BS. Generally, the one-dimensional arrangements in all three crystals comprise the same ribbon formations. However, the further organization of the ribbons is significantly different in G·CBS. We analyse the donor and acceptor efficacy of the additional functional group to disrupt some of the basic hydrogen bonds between the guanidinium and the sulfonium portions in G·BS. Since the carboxylic group introduces a mismatching of the sites on the counter ions, the changes in the symmetry relations essentially depend upon the topology of the substituent X, which results in modified packing patterns. All engineering peculiarities are analysed with respect to the symmetry constraints and geometrical demands of the packing forces.

Synthesis, crystal structures, spectroscopic studies and antibacterial properties of a series of mononuclear cobalt(III) Schiff base complexes

New complexes of cobalt(III) with the tridentate and tetradentate Schiff base ligands: 3-methoxy-2-{(Z)[(2-hydroxyphenyl)imino]methyl}phenol (H2L1), 4-[(2-hydroxyphenyl)imino]-2-pentanone (H2L2); and 2-((E)-1-(2-((E)-1-(2-hydroxy-4,5-dimethylphenyl)ethylideneamino)ethylimino)ethyl)-4,5 dimethylphenol (H2L3), namely [CoIII(L1)(N-MeIm)3]PF6 (1), [CoIII(L1)(py)3]ClO4 (2), [Co(L1)(py)3][Co(L1)2] (3) and [CoIII(L2)(N-MeIm)3]PF6 (4) and [Co(L3)(N-MeIm)2]PF6 (5), were synthesized and characterized by physico-chemical and spectroscopic methods. The crystal structures of the complexes were determined by X-ray crystallography. In each of these complexes, the cobalt(III) centre has a slightly distorted octahedral environment, utilizing all available coordination centres of the ligands. The complexes were also screened for in vitro antibacterial activities against four human pathogenic bacteria, and their minimum inhibitory concentrations indicated good antibacterial activities.

IV. Thionalogues of sparteine lactams. (+)-15-Thionosparteine and its perchlorate salt

Abstract (+)-15-Thionosparteine and its perchlorate have been obtained and characterized by IR and NMR spectroscopy as well as by X-ray diffraction analysis. Introduction of the thiolactam group into the cis-quinolizidine part of the sparteine skeleton causes conformational rigidity of this fragment in the solid state. Moreover, the conformations in solution, established by NMR and in the solid state are similar.

Synthesis, crystal structures and antibacterial studies of oxidovanadium(IV) complexes of salen-type Schiff base ligands derived from meso-1,2-diphenyl-1,2-ethylenediamine

A series of new derivatives and previously reported Schiff base ligands and their oxidovanadium(IV) complexes were synthesized, characterized and tested as potential antibacterial agents against four human pathogenic bacteria. These N2O2 type Schiff base ligands were derived from the condensation of meso-1,2-diphenyl-1,2-ethylenediamine with different salicylaldehyde derivatives, and their metal complexes were obtained from the reaction of these ligands with bis(acetylacetonato)oxidovanadium(IV). Our studies showed that the metal complexes had moderate antibacterial activity, and this activity was higher than that of the free ligands against both Gram-positive and Gram-negative bacteria. Besides, it was found that the presence of more substituents on the ligands increases the antibacterial activities of both the free ligands and their complexes. The crystal structures of H2L4 and its corresponding complex VOL4 were determined by X-ray crystallography.

(1RS,6SR)-Ethyl 4,6-bis­(4-fluoro­phen­yl)-2-oxocyclo­hex-3-ene-1-carboxyl­ate

In the crystal structure of the title compound, C21H18F2O3, the cyclohexene ring has a slightly distorted sofa conformation; the two benzene rings are inclined by 76.27 (8)° and their planes make dihedral angles of 16.65 (10) and 67.53 (7)° with the approximately planar part of the cyclohexenone ring [maximum deviation 0.044 (2) Å, while the sixth atom is displaced by 0.648 (3) Å from this plane]. In the crystal, weak intermolecular C—H⋯O, C—H⋯F and C—H⋯π interactions join molecules into a three-dimensional structure.

(1RS,6SR)-Ethyl 4-(4-chloro­phen­yl)-6-(4-fluoro­phen­yl)-2-oxocyclo­hex-3-ene-1-carboxyl­ate toluene hemisolvate

In the crystal structure of the title compound, C21H18ClFO3·0.5C7H8, the toluene solvent molecules occupy special positions on centres of symmetry, and consequently are disordered across this site. The cyclohexene ring has a slightly distorted sofa conformation; the two benzene rings are inclined by 72.90 (7)° and their planes make dihedral angles of 30.09 (10) (chlorophenyl) and 88.13 (6)° (fluorophenyl) with the approximately planar part of the cyclohexenone ring [maximum deviation from plane through five atoms is 0.030 (2) Å, the sixth atom is 0.672 (3)Å out of this plane]. Weak intermolecular C—H⋯O and C—H⋯X (X = F, Cl) interactions join molecules into a three-dimensional structure. Also, a relatively short and directional C—Cl⋯F—C contact is observed [Cl⋯F = 3.119 (2) Å, C—Cl⋯F = 157.5 (2)° and C—F⋯Cl 108.3 (2)°]. The solvent molecules fill the voids in the crystal structure and are kept there by relatively short and directional C—H⋯π interactions.

Charge-density analysis using multipolar atom and spherical charge models: 2-methyl-1,3-cyclopentanedione, a compound displaying a resonance-assisted hydrogen bond.

The experimental charge-density distribution in 2-methyl-1,3-cyclopentanedione in the crystal state was analyzed by synchrotron X-ray diffraction data collection at 0.33 Å resolution. The molecule in the crystal is in the enol form. The experimental electron density was refined using the Hansen-Coppens multipolar model and an alternative modeling, based on spherical atoms and additional charges on the covalent bonds and electron lone-pair sites. The crystallographic refinements, charge-density distributions, molecular electrostatic potentials, dipole moments and intermolecular interaction energies obtained from the different charge-density models were compared. The experimental results are also compared with the theoretical charge densities using theoretical structure factors obtained from periodic quantum calculations at the B3LYP/6-31G** level. A strong intermolecular O-H···O hydrogen bond connects molecules along the [001] direction. The deformation density maps show the resonance within the O=C-C=C-OH fragment and merged lone pair lobes on the hydroxyl O atom. This resonance is further confirmed by the analysis of charges and topology of the electron density.

(1RS,6SR)-Ethyl 4-(2,4-dichloro­phen­yl)-6-(4-fluoro­phen­yl)-2-oxocyclo­hex-3-ene-1-carboxyl­ate

There are two symmetry-independent molecules in the asymmetric unit of the title compound, C21H17Cl2FO3. Both these molecules are very similar: the normal probability plots for bond lengths, angles and even for torsion angles show that the differences are of a statistical nature. A pseudocentre of symmetry is located between the symmetry-independent molecules at [0.245 (1), 0.535 (19), 0.909 (1)]. The cyclohexene rings have slightly distorted sofa conformations in both molecules and the two benzene rings are inclined by dihedral angles of 61.33 (14) and 62.85 (14)°. In the crystal, relatively short intermolecular C—H⋯O interactions join molecules into homomolecular (i.e. ⋯AAA⋯ and ⋯BBB⋯) chains along the b axis. These chains are interconnected by further heteromolecular C—H⋯O interactions.

1-Methyl­piperazine-1,4-diium dipicrate

In the crystal structure of the title compound [systematic name: 1-methylpiperazine-1,4-diium bis(2,4,6-trinitrophenolate)], C5H14N2 2+·2C6H2N3O7 −, the ionic components are connected by relatively strong N—H⋯O hydrogen bonds into centrosymmetric six-membered conglomerates, which comprise two dications and four anions. Besides Coulombic interactions, only weak C—H⋯O interactions and some stacking between picrates (separation between the planes of ca. 3.4 Å but only a small overlapping) can be identified between these ‘building blocks’ of the crystal structure. The piperazine ring adopts a chair conformation with the methyl substituent in the equatorial position. In the picrate anions, the twist angles of the nitro groups depend on their positions relative to the phenolate O atom: it is much smaller for the NO2 groups para to the C—O− group [15.23 (9)and 3.92 (14)°] than for the groups in the ortho positions [28.76 (13)–39.84 (11)°].