Iwona Dąbkowska's research while affiliated with University of Gdansk and other places

The dissociative double photoionization of the isoxazole molecules has been investigated experimentally and theoretically. The experiment has been carried out in the 27.5-36 eV photon energy range using vacuum ultraviolet...

The manuscript presents the electrochemical characteristics of aza-12-crown-4 ethers substituted with an anthraquinone moiety. The pH-spectroscopic dependencies of these dyes have already been proven by us (part I). The aim of this work is to demonstrate pH-dependent electrochemical signaling capabilities of these ethers, which may be utilized as an alternative to their optical ones. This dualistic signaling nature makes the presented group of compounds potentially very attractive molecular recognition systems. Therefore, the detailed discussion of the effect of the structure of the macrocycle on the mechanism of electrode reactions provided here, seems to be crucial, as it may allow to design other systems of such diverse capabilities. The sensitivity of the electrophores to interactions with protons was thoughtfully scrutinized. Voltametric measurements presented new phenomena: the formation of three reduction peaks, which is unusual for quinones. Quantum chemical simulations allowed the attribution of these effects to the presence of amino groups in the macrocycle and their ability to form intramolecular hydrogen bonds. The combination of electrochemical, spectroscopic and acid-base properties of the studied compounds clearly demonstrates their versatility and potential applicability in new sensors.

Six novel amino acid chromophores were synthesized and their spectroscopic, acid-base, and electrochemical properties are discussed in this work. In studied compounds, selected amino acid residues (L-Aspartic acid, LGlutamic acid, L-Glutamine, L-Histidine, L-Lysine, L-Arginine) are attached to the 1-(piperazine) 9,10-anthraquinone skeleton via the amide bond between the carboxyl group of amino acid and nitrogen atomof the piperazine ring. All derivatives have been characterized using a variety of spectroscopic techniques (mass spectrometry, 1HNMR, UV–Vis, IR spectroscopy), acid-base (electrochemical and UV–Vis) titrations, and cyclic voltammetry methods. Basing on observed experimental effects, supported by quantum chemical simulations, the structureproperties links were established. They are indicative of the specific interactions within and/or in-between amino acid side groups,which are prone to formboth, intra- and intermolecular hydrogen bonds aswell as electrostatic interactions with the anthraquinone system.

The objective of the study is to determine the influence of a substituent on the spectroscopic and electrochemical properties of a series of novel 9,10‑anthraquinone piperidine and piperazine derivatives. We conducted UV–Vis spectroscopy, pH-spectroscopic titration, and cyclic voltammetry measurements with an interesting phenomenon observed in the case of di-substituted quinones. Compounds with substituents in position 1 and 8 exhibit a significant increase in the absorption intensity of the monoprotonated form. Spectroscopic studies in the conjunction with time-dependent density functional theory (TD-DFT) calculations were employed to explore the unusual behavior. The state-of-the-art quantum chemistry calculations including bulk solvent in the polarizable continuum model (PCM) enabled the study of prototropic tautomerization and its influence on the position of absorption bands. The results of cyclic voltammetry measurements allowed us to determine the deciding factor influencing the reduction – the number of substituents and the possibility of the hydrogen bond formation of the charged states.

Elimination of the excited hydrogen atoms H(n), n =4-7, and hydrogen migration in formation of the excited NH(A ³Π) free radicals in the photodissociation of pyridine, C5H5N, molecules have been studied over the 17.5-70 eV photon energy range. In the measurements the photon-induced fluorescence spectroscopy technique has been applied. Both fragments are produced through excitation of pyridine molecules into higher-lying superexcited Rydberg or doubly excited states. The mechanisms for fragmentation of pyridine into H(n) and NH(A ³Π) are discussed. Ab initio quantum chemical calculations have been performed to elucidate the hydrogen migration mechanism in the NH formation, which is not a self-contained unit in the structure of pyridine.