ANNEX IV. WG's Annual Summary
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ANNEX IV. WG’s annual summary (6) WG D36/001/06 Annual report Project title: Redox activity of host-guest, organometallic and molecular structures at electrode interfaces. II. Scientific report The joint research of host-guest complexes included the synthesis of several derivatives, in which the permethylated cyclodextrins were attached covalently to fullerene. The fullerene moiety was attached to the primary and also to the secondary cyclodextrin rings. Solubility of these compounds in water enabled us investigation of redox reactions of C60 in protic medium. The objective was the distinction of an intramolecular complexation from interactions C60-cyclodextrin between two molecules by electrochemical methods. Results were jointly published in Carbon. The redox activity of pesticides containing the nitroaromatic group is significantly increased by cationic catalysis. The joint research included very low frequency electrochemical impedance measurements combined with the modeling. We proved that under certain conditions the catalyzed electron transfer gives rise to the negative differential resistance. Such heterogeneous redox system yields spontaneous electric oscillations. Hence it is a suitable model system for natural periodic reactions. Results were jointly published in Electrochemica Acta. A series of new spiral-shaped organic dications was synthesized. The structure– properties relationships were sought in a series of [5]helquats having different number of methyl substitutents in several positons of aromatic rings. This study proved possible tuning of redox properties for applications of helquats as redox transfer mediators. Furthermore, these compounds were thoroughly investigated by EPR and electrochemical techniques seeking distinction between the formation of a charge transfer complexe and a complete electron transfer. The publication was accepted to Phys. Chem. Chem. Phys. journal The application of in-situ spectroelectrochemical methods involves a close cooperation with D35 action. Both partner laboratories achieved numerous results in the field 1 of interfacial organometallic redox chemistry. This yielded a review article in a high-impact journal. The combination of the reaction-oriented electrochemistry with the species-focussed spectroscopy in spectroelectrochemistry (SEC) allows a more complete analysis of electron transfer processes and redox reactions in general. Selected examples involving UV-VIS-NIR and IR absorption spectroscopy as well as electron paramagnetic resonance (EPR) illustrate the potential and the applicability of this technique. Original results obtained this year are described below. Research of the electron transfer in new organometallic compounds included phosphorescent cyclometalated heteroleptic iridium(III) phenylpyridinato (ppy) complexes containing luminescent 1-pyridylimidazo [1,5-α]pyridine (pip) ligands. Excitation of + [[Ir(ppy)2 (pip)] in acetonitrile solutions at room temperature results in a dual luminescence, strongly quenched by O2. Four complexes show, in absence of O2, a high-energy emission (assigned to a 3MLLCT transition) with two maxima in the blue region of the visible spectra, and a second structured emission (assigned largely to a 3LC π–π* transition. New tris(ferrocenylcopper) compounds {(µ3-dqp)[Cu(dppf)]3}(BF4)3, dppf = 1,1’- bis(diphenylphosphinoferrocene), dqp = hexamethyl-, hexachloro- and un-substituted diquinoxalino[2,3-a:2’,3’-c]phenazine = hexaazatrinaphthylene (HATN), undergo at least two differently separated reversible one-electron reductions and three very closely spaced one- electron oxidations. While the latter are attributed to the stepwise ferrocene→ferrocenium conversions, the first electron addition occurs in the ligand bridge to yield EPR detectable radical complexes. Reversible steps reveal very low energy transitions for the reduced forms in agreement with the frontier MO arrangement. Our WG published 7 papers and 9 congress presentations with abstracts. Two STSM were granted. Seven other exchange visits were financed from other local sources. Publications: 1. L. Pospíšil, M. Hromadová, M. Gál, J. Bulíčková, R. Sokolová, S. Filippone, J. Yang, Z. Guan, A. Rassat, Y. Zhang Redox Potentials and Binding Enhancement of Fullerene and Fullerene-Cyclodextrin Systems in Water and Dimethylsulfoxide. Carbon, 48 (2010) 153. 2. M. Hromadová, L. Pospíšil, R. Sokolová, N. Fanelli New electrochemical oscillator based on the cation-catalyzed reduction of nitroaromatic radical anions. Electrochim. Acta, 54 (2009), 4991 2 3. L. Adriaenssens, L. Severa, T. Šálová, I. Císařová, R. Pohl, D. Šaman, S. V. Rocha, N. S. Finney, L. Pospíšil, P. Slavíček, F. Teplý Helquats: A Facile, Modular, Scalable Route to Novel Helical Dications Chemistry Eur. J., 15 (2009) 1072. 4. L. Pospíšil, M. Hromadová, M. Gál, M. Valášek, N. Fanelli, V. Kolivoška Irregular Polarographic Currents Obey Feigenbaum Universality Route from Order to Chaos Coll. Czechoslovak Chem. Commun, DOI: 10.1135/cccc2009120 5. G. Volpi, C. Garino, L. Salassa, J. Fiedler, K. I. Hardcastle, R. Gobetto, C. Nervi Cationic Heteroleptic Cyclometalated Iridium Complexes with 1-Pyridylimidazo [1,5- α]Pyridine Ligands: Exploitation of an Efficient Intersystem Crossing Chem. Eur. J, 15 (2009), 6415. 6. S. Roy, B. Sarkar, C. Duboc, J. Fiedler, O. Sarper, F. Lissner, S. M. Mobin, G. K. Lahiri, W. Kaim Heterohexanuclear (Cu3Fe3) Complexes of Substituted Hexaazatrinaphthylene - (HATN) Ligands: Twofold BF4 Association in the Solid and Stepwise Oxidation (3 e) or Reduction (2 e) to Spectroelectrochemically Characterized Species Chem. Eur. J. 15 (2009), 6932 7. W. Kaim, J. Fiedler Spectroelectrochemistry: the best of two worlds Chem. Soc. Rev. 38 (2009), 3373 Congress presentations and abstracts: 1. R. Sokolová, M. Hromadová, J. Ludvík, L. Pospíšil, S. Giannarelli: “ The Autoprotolysis in Reduction Mechanism of Substituted Benzonitriles“ in The 60th Annual Meeting of the International Society of Electrochemistry, Symposium S10 – Molecular Electrochemistry: In its own right and in service to related research areas, Cd of Abstracts, Beijing, China, August 16 – 21, 2009, p 8. 2. L. Pospíšil, M. Gál, , M. Hromadová, R. Sokolová, J. Bulíčková, Y. Zhang , A. Rassat, S. Filippone, J. Yang, Z. Guan: ”Water-Soluble Fullerene Compounds Facilitate Nitrogen Fixation“ in The 60th Annual Meeting of the International Society of Electrochemistry, Symposium S10 – Molecular Electrochemistry: In its own right and in service to related research areas, Cd of Abstracts, Beijing, China, August 16 – 21, 2009, p 29. 3. M. Hromadová, L. Pospíšil, R. Sokolová, S. Giannarelli, M. Gál: “ Focus on the Fate of Bifenox Anion Radical in the Presence of Cyclodextrin Cavities“ in The 60th Annual Meeting of the International Society of Electrochemistry, Symposium S10 – Molecular Electrochemistry: In its own right and in service to related research areas, Cd of Abstracts, Beijing, China, August 16 – 21, 2009, p 42. 4. R. Sokolová, I. Degano, M. Valášek, J. Fiedler, M. Hromadová, L. Pospíšil, J. Bulíčková, M. Gál, M. P. Colombini: „The Oxidation of Natural Dye Quercetin“ in International Symposium on Frontiers of Electrochemical Science and Technology, Book of Abstracts, Xi’an, August 12 – 15, 2009, O08. 5. V. Kolivoška, M. Valášek, L. Pospíšil, R. Sokolová, M. Hromadová: „On the Adsorption of Extended Viologens at the Mercury-Solution Interface.“ in International Symposium on Frontiers of Electrochemical Science and Technology, Book of Abstracts, Xi’an, China, August 12 – 15, 2009, O14. 6. L. Pospíšil, F. Teplý, M. Gál, L. Adriaenssens, M. Horáček, L. Severa, ElectronTransfer in Helical Polyaromatics in International Symposium on Frontiers of Electrochemical 3 Science and Technology, Book of Abstracts, Xi’an, China, August 12 – 15, 2009, O06. 7. L. Pospíšil, M. Gál, M. Horáček, F. Teplý, L. Adriaenssens, L. Severa, Structure- Reactivity Relationships in Electron Transfers of Helical Polyaromatic Dications, COST Chemistry D36 Workshop, Structural-performance relationships at the surface of functional materials, Book of Abstracts, Benahavis, Malaga, Spain, 21.-23.10.2009, p.123. 8 Z. Guan, J. Yang, Y. Wang, F. Moussa, L. Pospíšil, Y. Zhang, Synthesis of novel 2:1 permethyulated-cyclodextrin-fullerene conjugates, COST Chemistry D36 Workshop, Structural-performance relationships at the surface of functional materials, Book of Abstracts, Benahavis, Malaga, Spain, 21.-23.10.2009, p.141. 9. G. Volpi, J. Fiedler, L. Pospíšil, M. Sandroni, C. Garino, R. Gobetto, G. Viscardi, C. Nervi, Electrochemical functionalization of glassy carbon electrode surfaces by organometallic moieties. COST Chemistry D36 Workshop, Structural-performance relationships at the surface of functional materials, Book of Abstracts, Benahavis, Malaga, Spain, 21.-23.10.2009, p.143 II A Innovative networking Participating laboratories gained a certaindegree of an innovative knowledge from sharing expertize in different fields. One example is the publication [1]. Previous research by a laboratory specialized in synthesis could not resolve a problem of supramolecular protection of reactive forms of fullerene. A joint experiments brought results by performing high sensitivity low-frequency impedance measurements, which could discriminate subtle effects of intramolecular interactions. It is expected that those derivatives may find application on pharmacology and other fields. The COST action promoted launching national and bilateral projects involving several institutes participating in this D36 project.