Marek Pietraszkiewicz

Chiral discrimination of amino acids and their potassium or sodium salts by optically active crown ether derived from d-mannose

Chiral naphtho-18-crown-6 incorporating α-methyl d-mannopyranoside unit exhibits a pronounced chiral discrimination of amino acids in their zwitterionic form, or as potassium and sodium salts in transport across the bulk liquid membrane containing the carrier, as well as in the extraction experiments from the water phase to chloroform phase containing the receptor. The dl selectivity strongly depends on the species used (neutral amino acids, or their salts), and in some cases the reversed selectivity within the same amino acid enantiomers has been observed, indicating the influence of the cation involved.

Synthesis of chiral diaza-crown ethers incorporating carbohydrate units

Abstract A synthesis of a novel chiral diaza crown ethers derived from α-D-glucose, α-D-mannose, and α-D-galactose in two alternative pathways is described.

Unusual, Solvent Viscosity-Controlled Tautomerism and Photophysics: Meso-Alkylated Porphycenes

Stationary and time-resolved studies of 9,10,19,20-tetramethylporphycene and 9,10,19,20-tetra-n-propylporphycene in condensed phases reveal the coexistence of trans and cis tautomeric forms. Two cis configurations, cis-1 and cis-2, play a crucial role in understanding the excited-state deactivation and tautomer conversion dynamics. The trans-trans tautomerization, involving intramolecular transfer of two hydrogen atoms, is extremely rapid (k ≥ 10(13) s(-1)), both in the ground and lowest electronically excited states. The cis-1-trans conversion rate, even though the process is thermodynamically more favorable, is much slower and solvent-dependent. This is explained by the coupling of alkyl group rotation with the hydrogen motion. Excited-state deactivation is controlled by solvent viscosity: the S(1) depopulation rate decreases by more than 2 orders of magnitude when the chromophore is transferred from a low-viscosity solution to a polymer film. Such behavior confirms a model for excited state deactivation in porphycene, which postulates that a conical intersection exists along the single hydrogen transfer path leading from the trans to a high energy cis-2 tautomeric form. For this process, the tautomerization coordinate includes not only hydrogen translocation but also large-amplitude twisting of the two protonated pyrrole moieties attached to the opposite sides of the ethylene bridge.

Luminescence intensification of lanthanide complexes by silver nanoparticles incorporated in sol-gel matrix

Abstract We present how the luminescence of europium RR-2-P-oxides complexes can be increased by interaction of electronic levels of the complex with the radiation field of silver nanoparticles (NPs). The procedure by which silver NPs are formed in a sol-gel polyurethane matrix precursor was elaborated. The formed Ag NPs were combined with Eu complex incorporated in ormocer matrix. The emission spectra of the complexes without silver NPs were compared with spectra of the same complexes with addition of silver NPs. As the result of the interaction of the electronic levels of lanthanide ligands with silver plasmons, dramatic increase of luminescence was observed.

Luminescent properties of silica and zirconia xerogels doped with europium(III) salts and europium(III) cryptate incorporating 3,3′-biisoquinoline-2,2′-dioxide

Eu+3 cryptate with 3,3′-biisoquinoline-2,2′-dioxide unit was incorporated into glass films consisting of zirconia dioxide and into hybrid ormosil films. The absorption and the emission intensities of the europium complex were compared to the intensity of the non-complexed europium ion in the films. The transition probabilities of the complex are increased as a result of the mixing of the europium orbitals with the ligand orbitals. The emission is additionally increased as the non-radiative relaxation is diminished by the cage effect.

Rare earth ions, their spectroscopy of cryptates and related complexes in sol-gel glasses

The paper is devoted to the memory of my teacher and friend Christian K. Jorgensen who has written the pioneering works on complexes of Rare Earths (RE).

Potentiometric detection of organic acids in liquid chromatography using polymeric liquid membrane electrodes incorporating macrocyclic hexaamines.

Potentiometric detection employing coated-wire electrodes was applied to the determination of organic acids in liquid chromatography (LC). Poly(vinyl chloride)-based liquid membranes, incorporating lipophilic macrocyclic hexaamines as neutral ionophores were used as electrode coatings. The selectivity and sensitivity of the macrocycle-based electrodes were found to be superior to an electrode based on a lipophilic anion exchanger (a quaternary ammonium salt). Sensitive detection was obtained for the di- and tricarboxylic acids tartaric, malonic, malic, citric, fumaric, succinic, pyruvic, 2-oxoglutaric and maleic acids after separation in reversed-phase LC. Detection limits (signal/4sigmanoise=3) of 6 pmol for malonic acid and 2 pmol for maleic acid were attained. The detection was explained using a molecular recognition model. The hexaamine-based potentiometric electrodes had a 1-s response time at 1 ml min(-1) flow-rates. They were stable for at least 4 months, with an intra-electrode variation of 3.2% (n=5).

Luminescence of europium(III) compounds in zirconia xerogels

Abstract Incorporation of europium(III) compounds: the oxide and dibenzoylmethane chelate (Eu(DBM) 3 ) into zirconia xerogel glasses resulted in luminescent materials in which the DBM chelate was the most efficient in luminescence intensity. The luminescence intensity was even stronger in hybrid xerogels prepared from zirconium tetrapropoxide and 3-glycidoxypropyl-trimethoxysilan.

Improvement of emission intensity in luminescent materials based on the antenna effect

Abstract Ternary Eu(III) complexes with macrobicyclic and acyclic ligands+co-ligands were encapsulated in silica or methylated silicate xerogels. Additionally, deuterated reagent and solvent were used in the sol–gel procedure. This preparation method with moderate thermal treatment reduced the concentration of OH groups in the materials and simultaneously improved their photophysical properties, i.e. increased luminescence intensity and prolonged luminescence lifetime. The best results were obtained for the Eu(III) complex with a cryptand of the [biqO2·2·2]+1,10-phenanthroline type (where biqO2=3,3′-biisoquinoline-2,2′-dioxide) immobilized in methyl-modified silicate xerogel. The effective luminescence properties of this sample make it a promising candidate for use as a luminescent material.

Investigations of the spectral properties of lanthanide(III) complexes with 3,3′-bi-isoquinoline-2,2′-dioxide (biqO2) and a biqO2-cryptate in solution, solids, and gels

Abstract Increasing interest has been observed in the spectroscopic properties of lanthanide ions in cryptates and heteroaromatic ligands where the lanthanide ions are encapsulated into the ligand structure [B. Alphov, J.M. Lehn, G. Matkis, Angen. Chem. 99 (1987) 259; J.M. Lehn, in: V. Balzani (Ed.), Supramolecular Photochemistry, Reidel, Dordrecht, 1987, pp. 29–42; N. Sabbatini, S. Perathoner, V. Balzani, B. Alpha, J.M. Lehn, in: V. Balzani (Ed.), Supramolecular Photochemistry, Reidel, Dordrecht, 1987, pp. 187–206]. Of special interest are those cryptates and chelating ligands in which efficient energy transfer between the ligands and the rare-earth ion takes place. The goal of the present studies is the description of the best conditions for this intra-system energy transfer in two types of compounds with 3,3′-biisoquinoline-2,2′-dioxide (biqO 2 ), and for a cryptate incorporating biqO 2 . Results are reported for these complexes prepared in water and non-aqueous solutions, and in gels obtained by different methods. Spectroscopic methods, including absorption, emission and excitation spectra, at 293 and 77 K were used to characterize the type and symmetry of the complexes formed in solutions and gels under different conditions (pH and concentration). It is demonstrated that the type of solvent used in the sol–gel process affects the emission intensity through perturbation of the ligand:metal electronic energy levels, and the symmetry and stability of the complexes. Correlation of the solid state spectroscopic results with those in solution and gel for Eu(III) ions, illustrates the role of the energy back transfer process in emission quenching. This is found to be temperature dependent.