Anna Skwierawska

STEREOCHEMISTRY OF 16-MEMBERED AZO- AND AZOXYCROWN ETHERS. STRUCTURES OF THEIR SANDWICH POTASSIUM IODIDE COMPLEXES

Abstract16-Membered dibenzoazo- and dibenzoazoxycrown ethers have been synthesized. The Z and E isomers of the azocrown compound have been separated and the geometry of the –N=N– and –-N(O)=N–- groups determined. Potassium iodide complexes of the azo- and azoxycrown ethers were obtained and their structures were determined by the X-ray method. The crystal of the azocrown ether complex is triclinic, space group P¯1, a = 21.071(5), b = 12.112(4), c = 8.757(2) Å α = 81.28(2), β = 84.66(2), γ = 107.49(2)°. The azoxycrown ether complex is monoclinic, space group C2/c, a = 15.648(3), b = 19.597(4), c = 14.651(3) Å; β = 111.30(3).

Synthesis and spectroscopic properties of new bis-tetrazoles

Syntheses of N,N′-phenyltetrazole podands link with aliphatic chains containing oxygen, nitrogen and sulphur atoms, are described. The complexing properties of these compounds towards metal cations (Fe2+, Cu2+, Zn2+, Co2+, Ni2+) were investigated by absorption and infrared spectroscopy. The UV–Vis titrations were performed to estimate the stability constant values of the respective complexes with Cu2+ ion. Changes in UV–Vis absorption spectra and IR spectra of compound 6 under various concentrations of Cu2+ ion in methanol suggest formation of very unstable complex. The structure of ligand 2 has been deduced by X-ray crystallography.

Functionalization of Electrode Surfaces with Monolayers of Azocompounds and Gold Clusters

Properties of monolayers of azocrown compound self-assembled on gold substrates were studied using voltammetry and scanning tunneling microscopy. The surface concentrations of this compound in monolayers were determined from the area of the voltammetric reduction peaks. The area per one molecule estimated from voltammetry experiments is 0.65 nm2. This value was comparable with the limiting molecular area of the compound in the Langmuir–Blodgett film at the air–water interface. We also observed the presence of gold clusters and other gold structures by STM when a gold electrode modified with azocrown compound was dipped into the tetrachloroaurate solution. Even better spectra of clusters were obtained following one voltammetric scan in the range 0.5 to −0.6 V. After more cycles or if we condition the electrode at 0.4 V the clusters aggregate into wires.

The Synthesis of 1,4,7,10-Tetraazacyclododecanes with Acetylsalicylic Side Arm as Potential Cobalt(II) Fluorophores

New derivatives of 1,4,7,10-tetraazacyclododecanes have been synthesized. The coordination properties toward Co2+ of these ligands have been studied by means of spectroscopic methods. The stability constants of cobalt complexes with ligand L-1 and L-2were determined. Unusual complexes with a 2:1 (L:Co2+) stoichiometry have been found.

Chromogenic derivatives of new bis(phenylhydrazono-1H-tetrazol-5-yl-acetonitriles) – synthesis and properties

Derivatives of bis(phenylhydrazono-1H-tetrazol-5-yl-acetonitriles) with oxygen and sulphur atoms in the structure of aliphatic chains were successfully synthesised. The correlation between the ligand structure and its complexation properties was investigated by absorption spectroscopy. The formation of complexes of presented compounds with metal cations (Cu2+, Ni2+, Zn2+, Co2+, Fe2+ and Pb2+) was studied. Ligands 5–8 were additionally applied as ion carriers in ion-selective membrane electrodes. Membranes of ion-selective electrodes doped with these ligands are selective to Cu2+ and Pb2+ cations.

Convenient synthesis of novel mono- and bi-functional fluorescent 1,4,7,10-tetraazacyclododecanes

Abstract The synthesis of 1,4,7,10-tetraazacyclododecanes possessing different electrodonor properties is described.

Improvement of opipramol base solubility by complexation with β-cyclodextrin

Abstract Opipramol (OPI), a tricyclic antidepressant and anxiolytic compound, is administered orally in the form of a dihydrochloride. Salt form of the drug has a higher solubility in water and hence bioavailability and stability. A similar effect can be achieved by closing the hydrophobic part of the drug molecule in the cyclodextrin cavity. The paper presents opipramol inclusion complexes with beta-cyclodextrin (β-CD) in 1:1 molar ratio. Studies on the formation of inclusion complexes were carried out both in solution and in the solid state. The formation and physicochemical characterisation of the complexes were determined by UV spectroscopic measurement (UV–vis), Fourier Transform Infrared (FTIR) Spectroscopy, 1H Nuclear Magnetic Resonance (1H NMR, 2D NOESY NMR), thermoanalytical methods (TGA – Termogravimetric analysis, DSC – differential scanning calorimetry), X-ray diffractometry (XRD) and scanning electron microscopy (SEM). The phase solubility profile with β-CD was classified as the AN- type, indicating the formation of the inclusion complex with a drug.

Synthesis, structural and spectroscopic properties of asymmetric Schiff bases derived from 2,3-diaminopyridine

Two Schiff base derivatives, 4-(2-amino-3-pyridyliminomethyl)phenol (I) and 3-(2-amino-3-pyridyliminomethyl)nitrobenzene (II), were synthesised and characterised by spectroscopy. The structure of I was determined by single crystal X-ray diffraction studies. The asymmetric Schiff base derived from 2,3-diaminopyridine selectively recognise transition and heavy metal cations, and some anion. Ligands I and II form stable complexes with Cu2+, Zn2+, Pb2+, Al3+ whereas ligand I also binds F~ ions. The stoichiometry for the host: cation is 1: 1 and 2: 1. The addition of F~ ion in CH3CN to ligand I causes a colour change of the solution from colourless to yellow. The binding behaviour of ligand I towards several ions was investigated using density functional theory calculations.

Degradation kinetics and mechanism of pentoxifylline by ultraviolet activated peroxydisulfate

Degradation of pentoxifylline (PTX) by sodium peroxydisulfate (SPDS) assisted by UV irradiation has been investigated in deionized water. The treatment was more favorable over direct photolysis or peroxydisulfate oxidation alone. The effects of various parameters, including different dosage of oxidant agent, PTX concentration, initial solution pH levels, and the presence of inorganic ions like chloride, nitrate and carbonate have been evaluated. The rate of PTX decomposition depends on the oxidant agent dose. The highest degradation was determined at pH 10.5, which can be explained by the generation of additional hydroxyl radicals (HO˙) in the reaction between sulfate radicals and hydroxide ions. The presence of inorganic ions, especially the carbonate ions quench valuable sulfate radicals and have successfully retarded the PTX decomposition. Six PTX oxidation products were identified using UPLC-QTOF-MS for trials in a basic environment. The main degradation product (3,7-dimethyl-6-(5-oxohexyloxy)-3,7-dihydro-2H-purin-2-one) was isolated by column chromatography and identified by 1HNMR and LC MS analyzes.

Synthesis and properties of new N,N′-phenyltetrazole podand

The synthesis of a new chromogenic N,N′-phenyltetrazole receptor is reported here. The cationbinding properties of this receptor in solution were investigated by naked-eye colour change, electrochemical methods and UV-Vis spectroscopy in various solvents (CH3CN, dimethylsulphoxide (DMSO), DMSO/H2O, CH3CN/H2O and CH3CN/MeOH). In addition, the receptor was used as a sensing material in ion-selective membrane electrodes. The selectivity and sensitivity of these electrodes towards alkali, alkali-earth, transition and heavy metal cations in aqueous solution were tested. The relation between the carrier structure and membrane plasticisers was investigated.