Laboratory of EPR spectroscopy

Faculty of Chemical and Food Technology

Department/Institute: Institute of Physical Chemistry and Chemical Physics
Contact persons:       Prof. Marian Valko, DSc, Prof. Peter Rapta, DSc
Contact:                   +421 2 5932 5750, +421 2 5932 5537,
E-mail:                     marian.valko@stuba.sk, peter.rapta@stuba.sk
web page:                 http://www.chtf.stuba.sk/kfch/indexe.php

Description:

Structure and reactivity of paramagnetic species in the chemical, biological and photochemical systems with emphasis on the area of the free-radical chemistry. The EPR laboratory is established as the center of EPR spectroscopy in Slovakia. Research is focused on the structure and reactivity of a series of model coordination compounds in different charge states mimicking natural enzyme activity, as well as complex mixtures of antioxidants in the absence or the presence of coordination compounds in solutions. Spectroelectrochemical techniques, especially in situ EPR and UV-Vis-NIR spectroelectrochemistry is applied in these studies. Experimental results are correlated with quantum chemical calculations, including interpretation and simulation of complex EPR spectra. In the photo-induced reactions, the studies are focused to the primary radical products formed upon photoexcitation of organic compounds and their heterogeneous suspensions with e.g. titanium dioxide, and to the homogeneous systems applying the EPR spin trap technique. Attention is devoted to studies of the interaction of redox active metals with drugs and natural substances. Protein metal-binding active sites are studied by the multifrequency EPR spectroscopy (S-band, L-band, Q-band).

 

Projects:

• Biologically active compounds in different charge states and their consecutive reactions in solutions followed by simultaneous spectroelectrochemical techniques (VEGA 1/0307/14)
• Study on electron transfer processes in natural and synthetic systems: structure-reactivity relationship (VEGA 1/0289/12)
• Photoinduced processes of natural and synthetic heterocyclic compounds with biological impact (APVV-0339-10; http://www.chtf.stuba.sk/kfch/APVV-0339-10/index.php)
• Interaction of redox active metals with neuro-protective agents: a way to combat oxidative stress in neurological disease? (VEGA 1/0765/14)

 

Selected Publications:

1.    Rapta, P., Popov, A. A., Yang, S., Dunsch L.: The Charged States of Sc3N@C68: An in situ Spetroelectrochemical Study of the Radical Cation and Radical Anion of a Non-IPR Fullerene.  J. Phys. Chem. A 112 (2008) 5858-5865.

2.    Zalibera, M., Popov, A. A., Kalbáč, M., Rapta, P., Dunsch L.: The Extended Wiev of The Empty C2(3)-C82 Fullerene: Isolation, Spectroscopic, Electrochemical and Spectroelectrochemical Characterization and DFT Calculations. Chem. Eur. J. 14 (2008) 9960-9967.

3.    Brezová, V., Šlebodová, A., Staško, A.: Coffee as a source of antioxidants: An EPR study. Food Chem. 114 (2009) 859-868.

4.    Brezová, V., Vrecková, Z., Billik, P., Čaplovičová, M., Plesch, G.: Photoactivity of mechanochemically prepared nanoparticulate titanium dioxide investigated by EPR spectroscopy. J. Photochem. Photobiol. A 206 (2009) 177-187.

5.   Jomova, K., Kysel, O., Madden, J.C., Morris, H., Enoch, S.J., Budzak, S., Young, A.J., Cronin M.T.D., Mazur, M., Valko, M.: Electron transfer from all-trans β-carotene to the t-butyl peroxyl radical at low oxygen pressure (an EPR spectroscopy and computational study). Chem. Phys. Lett. 478 (2009) 266-270.

6.    Matis, M., Rapta, P., Lukeš, V., Hartmann, H., Dunsch L.: Highly charged cations from N,N,N’,N’-tetrakis(4-aminophenyl)benzidine and its N,N,N’,N’-tetra-(4-methoxyphenyl-substituted homologue studied by thin-layer in situ ESR-UV/Vis/NIR spectroelectro­chemistry. J. Phys. Chem B 114 (2010) 4451-4460.

7.    Chen, N., Klod, S., Rapta, P., Popov, A. A.,  Dunsch L.: A direct arc synthesis of C60H2(C3H5N) - a Pyrrolo C₆₀ Fullerene Hydride with Unusual Redox Properties. Chem. Mater. 22 (2010) 2608-2615.

8.   Arion, V. B., Rapta, P., Telser, J., Shova, S. S., Breza, M., Luspai, K., Kozisek, J.: Syntheses, Electronic Structures, and EPR/UV-Vis-NIR Spectroelectrochemistry of Nickel(II), Copper(II), and Zinc(II) Complexes with a Tetradentate Ligand Based on S-Methylisothiosemicarbazide.       Inorg. Chem. 50 (2011) 2918-2931.

9.    Barbieriková, Z., Bella, M., Lietava, J., Dvoranová, D., Staško, A., Füzik, T., Milata, V., Jantová, S., Brezová, V.: Spectroscopic characterization and photoinduced processes of 4-oxoquinoline derivatives. J. Photochem. Photobiol. A 224 (2011) 123-134.

10.  Jomova, K., Valko, M.: Free radicals, signal transduction, and human disease. in Oxidative Stress in Vertebrates and Invertebrates: Molecular Aspects of Cell Signaling, Editors: T. Farooqui, A. A. Farooqui, Wiley-Blackwell, New York, 2011, pp. 17-32.

11. Jomova, K., Valko, M.: Thermodynamics of free radical reactions and the redox environment of a cell. in Oxidative Stress: Diagnostics and Therapy, Editors: S. Andreescu, M. Hepel, American Chemical Society, Washington DC, 2012, pp. 71-82.

12.   Barbieriková, Z., Mihalíková, M., Brezová, V.: Photoinduced oxidation of sterically hindered amines in acetonitrile solutions and titania suspensions (An EPR Study).        Photochem. Photobiol. 88 (2012) 1442-1454.

13.   Staško, A., Lušpai, K., Barbieriková, Z., Rimarčík, J., Vagánek, A., Lukeš, V., Bella, M., Milata V., Zalibera, M., Rapta, P., Brezová V.: Stable Radical Trianions from Reversibly Formed Sigma-Dimers of Selenadiazoloquinolones Studied by In Situ EPR/UV−vis Spectroelectrochemistry and Quantum Chemical Calculations. J. Phys. Chem. A 116 (2012) 9919-9927.

14.   Arion, V. B., Dobrov, A., Gosch, S., Jakupec, M. A., Keppler, B. K., Rapta, P.: Ruthenium- and osmium-arene-based paullones bearing a TEMPO free-radical unit as potential anticancer drugs.  Chem. Commun. 48 (2012) 8559-8561.

15.   Arion, V.B., Platzer, S., Rapta, P., Machata, P., Breza, M., Vegh, D., Dunsch, L., Telser, J., Shova, S., Mac Leod, T.C.O., Pombeiro, A.J.L.: Marked stabilization of redox states and enhanced catalytic activity in galactose oxidase models based on transition metal S- methylisothiosemicarbazonates with -SR group in ortho position to the phenolic oxygen.          Inorg. Chem. 52 (2013) 7524-7540.

16.   Barbieriková, Z., Bella, M., Sekeráková, Ľ., Lietava, J., Bobeničová, M., Dvoranová, D., Milata, V., Sádecká, J., Topoľská, D., Heizer, T., Hudec, R., Czímerová, A., Jantová, S., Brezová, V.: Spectroscopic characterization, photoinduced processes and cytotoxic properties of substituted N-ethyl selenadiazoloquinolones.  J. Phys. Org. Chem. 26 (2013) 565-574.

17.   Saison, T., Gras, P., Chemin, N., Chanéac, C., Durupthy, O., Brezová, V., Colbeau-Justin, C., Jolivet, J.-P. New insights into Bi₂WO₆ properties as a visible-light photocatalyst. J. Phys. Chem. C 117 (2013) 22656-22666.

18.   Jomova, K., Lawson, M., Valko, M.: Mechanisms of antioxidant activity. in Food Oxidants and Antioxidants: Chemical, Biological, and Functional Properties, ed. G. Bartosz, CRC Press, Taylor & Francis group, Boca Raton, FL, 2013, pp. 325-342.

19.  Jomova, K., Valko, M. Health protective effects of carotenoids and their interactions with other biological antioxidants. Eur. J. Med. Chem. 70 (2013) 102-110.

20.   Di Paola, A., Bellardita, M., Palmisano, L., Barbieriková, Z., Brezová, V.: Influence of crystallinity and OH surface density on the photocatalytic activity of TiO₂ powders.            J. Photochem. Photobiol. A 273 (2014) 59-67.

Cooperation:

EPR team is collaborating not only with staff of different departments of Faculty of Chemical and Food Technology SUT and Slovak Academy of Sciences, but over the years he has been intensively involved in the cooperation with many institutions abroad, especially in Germany (IFW Dresden, TH Darmstadt, TU Munich) and Austria (University of Vienna, TU Graz). The partnership represents the spectroelectrochemical group in IFW Dresden, a group of leading inorganic chemists around Prof. V. Arion from University of Vienna, EPR scientific teams from Graz (Prof. G. Grampp, TU Graz, Austria),

Dr. M. Cronin and Prof. H. Morris from Univ. J. Moores in Liverpool, Dr. F. Kvasnik from UMIST in Manchester and Prof. J. Telser from the North West University in Chicago. The scientific cooperation results in the regular short- and long-term stays at the partners’ laboratories, frequently coupled with the supply of unique chemicals, experimental accessories and techniques to our laboratory, as well as in the preparation of international scientific contributions of high quality.

 

Photos:

Fig. 1: X-band EPR spectrometer (Bruker EMX, Germany)

Fig.2: Setup for in situ EPR/UV-vis/NIR spectroelectrochemistry connected to the Bruker EMX EPR spectrometer.