(Trifluoromethoxy)Phenylboronic Acids: Structures, Properties, and Antibacterial Activity

Three isomers of (trifluoromethoxy)phenylboronic acids were studied in the context of their physicochemical, structural, antimicrobial and spectroscopic properties. They were characterized by 1H, 13C, 11B and 19F NMR spectroscopy. The acidity of all the isomers was evaluated by both spectrophotometric and potentiometric titrations. The introduction of the -OCF3 group influences the acidity, depending, however, on the position of a substituent, with the ortho isomer being the least acidic. Molecular and crystal structures of ortho and para isomers were determined by the single crystal XRD method. Hydrogen bonded dimers are the basic structural motives of the investigated molecules in the solid state. In the case of the ortho isomer, intramolecular hydrogen bond with the -OCF3 group is additionally formed, weaker, however, than that in the analogous -OCH3 derivative, which has been determined by both X-Ray measurements as well as theoretical DFT calculations. Docking studies showed possible interactions of the investigated compounds with LeuRS of Escherichia coli. Finally, the antibacterial potency of studied boronic acids in vitro were evaluated against Escherichia coli and Bacillus cereus.

The assessment of the environmental hazard of isomers of 1,2,4-triazole phenolic derivatives for natural ecosystems

Its necessary to synthesize homologues of compounds frequently used in practice and to analyze their biological activity in laboratory experiments using screening tests that provide an integral assessment of biological responses to assess the effect of anthropogenic xenobiotics with different structures on ecosystems adjacent to agricultural complexes. We analyzed alcohol solutions of 2-(1H-1,2,4-triazolyl-methyl)phenol (ortho-isomer) and 4-(1H-1,2,4-triazolyl-methyl)phenol (para-isomer) in three concentrations: 0,0001; 0,001; 0.01 mg/ml using the Allium-test. The solvent was 0,1% isopropyl alcohol; the test object was Allium fistulosum L. The duration of the experiment was 5 days. Triazolide solutions significantly inhibited seed germination at all investigated concentrations. However, no significant differences were found between the isomers and the studied concentrations. Both isomers inhibited root growth at all concentrations tested. The toxicity of a triazolide containing an OH group in the para-position didnt change over the selected concentration range. For its ortho-isomer, toxicity increased with increasing concentration, reaching the toxicity of its homologue at a dose of 0,01 mg/ml. Both tested compounds significantly inhibited the proliferation of meristem cells as compared to the control. At the same time, no differences were observed in the effect of homologues with the OH-group in the para- and ortho-position on the value of the mitotic index. However, we found a paradoxical reaction: both homologues showed maximum cytotoxicity at a minimum concentration of 0,0001 mg/ml, and cytotoxicity decreased with increasing concentration compared to control. A triazolid containing an OH group in the para-position caused a block at the metaphase and anaphase stages at the lowest concentration. The specificity of its action disappeared with an increase in concentration, which was expressed in a general prophase and metaphase block. Its ortho-isomer inhibited cell division at all concentrations at the prophase stage. Both compounds are mutagenic. The number of chromosomal aberrations depended on both the structure of the compounds and their concentration. The para-homologue is less mutagenic than ortho. In the ortho-homologue, mutagenicity decreased slightly with increasing concentration. The highest mutagenicity was found for the ortho-homologue at its lowest concentration. The paper discusses possible mechanisms of action of isomers and their negative impact on plant organisms in ecosystems.

Silicalite-1, an adsorbent for 2-, 3-, and 4-chlorophenols

The adsorption of the three chlorophenol isomers, ortho, meta and para, by silicalite-1 has been studied at 30 °C, below the solubility (at the same temperature) in water. Large differences, up to 30 times, have been observed between the adsorption of the para- vs. the ortho-isomer. The difference of behavior observed between the isomers is assigned to the tendency to self-organization of the para-isomer. It seems probable that the adsorption sites are at the intersection channels. From a technical point of view, silicalite-1 seems a competitive adsorbent for p-chlorophenol.

Isomers of Diformyl[2.2]paracyclophane; X-Ray Structure Determinations of the Pseudo-ortho Isomer and Two Polymorphs of the Pseudo-meta Isomer

Pseudo-ortho- or 4,16-diformyl[2.2]paracyclophane (1) and two polymorphs of pseudo-meta- or 4,13-diformyl[2.2]paracyclophane (2) all display the usual features of [2.2]paracyclophane strain (lengthened C-C bonds and widened C-C(sp3)-C angles in the bridges, narrower sp2 ring angles at the bridgehead atoms, and flattened boat conformations of the rings). All bulk samples were racemates. Polymorph 2a crystallizes in space group P21/n with one molecule in a general position, whereas 2b crystallizes in space group C2 with two independent molecules, each with crystallographic twofold symmetry. All three molecules of 2 are different rotamers with respect to the formyl groups; in 2a one is endo and one exo to the neighbouring bridge, whereas in 2b both formyls are exo in one molecule and endo in the other. In all compounds, the packing patterns are preponderantly associated with C-H・ ・ ・O contacts. In 1 the molecules are connected to form tubes parallel to the short a axis. 2a consists of two interconnected layer structures. One is parallel to (100) and involves chains of molecules parallel to [01̄1]; the other is parallel to (001) and involves chains of molecules parallel to the b axis. 2b consists of two hexagonal layers, one for each independent molecule, parallel to (001). One layer contains bifurcated (C-H・ ・ ・ )2O systems, whereas the single H・ ・ ・O interactions in the other are long and markedly bent.

Electrospray mass spectrometry of isomeric tetrakis(N-alkylpyridyl)porphyrins and their manganese(III) and iron(III) complexes

Manganese(III) complexes of isomeric tetrakis(N-alkylpyridyl)porphyrins (N- alkyl = N- methyl , M or N- ethyl , E ), MnTM ( E )-2(3,4)- PyP 5+, are being developed as superoxide dismutase (SOD) mimics. Simultaneously, techniques for their purification, identification and characterization are being pursued. Electrospray mass spectrometry ( ESMS ) proved to be an excellent method for identification and characterization of this group of water-soluble cationic porphyrins. The multiply charged parent ion is observed for both the metal-free ligands and their corresponding manganese complexes. The other major peaks in the mass spectra result from loss of N-alkyl groups, reduction of the metal center, axial coordination of chloride or hydroxo ion in the case of the Fe porphyrin, loss of metal and deprotonation of pyrrolic nitrogens. As a result of inductive and resonance effects, which stabilize the ortho isomer, almost no loss of N-alkyl groups from the manganese complex or from its parent ligand was observed. The relative intensity of the multiply charged molecular ion Mn III TM -3(4)- PyP 5+/5 was 100% in the case of the meta and para isomers. Although manganese porphyrins display a low preference toward axial ligation, favorable electrostatics at the metal center of the ortho isomer gives rise to 100% relative intensity of the species that has chloride axially ligated at the manganese site, Mn III TM ( E )-2- PyPCl 4+/4. When the stronger preference of iron porphyrins toward axial ligation combines with the ortho effect, the monohydroxo iron porphyrin Fe III TM -2- PyP ( OH )4+/4 dominates the ESMS of an aqueous acetonitrile solution at pH 7.8.