XII Iberian Meeting of Electrochemistry XVI Meeting of the ...

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XII Iberian Meeting of Electrochemistry & XVI Meeting of the Portuguese Electrochemical Society PE 03 Evaluation of the antioxidant capacity of imidazoimidazole phenolic derivatives by cyclic voltammetry F. Gomes, A.P. Bettencourt, C. Correia, M.A. Carvalho, M.F. Proença Departamento de Química, Universidade do Minho, 4710-057, Braga, Portugal figs8@hotmail.com The human organisms are exposed to reactive species (ROS) and the action of free radicals can potentiate redox reactions that can cause several diseases [1,2]. The use of compounds with antioxidant activity is expected to be useful for the prevention and treatment of these diseases [1,2]. Therefore, there has been a growing interest in finding novel antioxidants in order to meet the requirements of pharmaceutical industries. It is also essential to have a simple and fast method to measure the antioxidant capacity of new compounds. So, several methods have been developed and used to evaluate the capacity of a compound to act as an antioxidant, including chemical and electrochemical methods [3]. Electrochemical approaches for evaluating antioxidant capacity used have been controlled-potential techniques [4, 5]. In this work several novel phenolic compounds based on an imidazoimidazole structure with potential antioxidant capacity were synthesized and their antioxidant activity evaluated by cyclic voltammetry. Cyclic voltammetry has been used to measure the ease of oxidation of the synthesized phenolic compounds and the anodic peak potential is employed as a predictor of antioxidant capacity. The effect of the nature of the substituent R and the position of hydroxyl groups in the substituent R 2 on the oxidation potentials of the compounds is evaluated. The antioxidant activities estimated by means of the anodic peak potentials were compared with data obtained for Trolox, a commercial derivative of vitamin E with high antioxidant activity routinely used as reference compound. R N NH R 1 N N CONH 2 Figure 1 - Imidazoimidazole structure Acknowledgments: F. Gomes acknowledges to F CT for the Integration into Research Grant, Centro de Química, Universidade do Minho. References [1] Valko, M.; Rhodes, C. J.; Moncola, J.; Izakovic, M.; Mazur, M. Chemico-Biological Interac. 2006, 160, 1. [2] Halliwell, B. Biochem. Pharmacol. 1995, 49, 1341. [3] Huang, D. ; Ou, B.; Prior, R.L., J. Agric. Food Chem. 2005, 53,1841. [4] Blasco, A.J.; Crevillén, A.G.; González, M.C.; Escarpa, A. Electroanalyis 2007, 19, 2275. [5] Bortolomeazz, R.; Sebastianutto, N.; Toniolo, R.; Pizzariello, A. Food Chem. 2007, 100, 1481. September, 811, 2010. ISEL - Lisbon 94
XII Iberian Meeting of Electrochemistry & XVI Meeting of the Portuguese Electrochemical Society PE 04 Complexes for N L O : Cyclic Voltammetry Study Ana M. Santos 1,2 , Paulo J. Mendes 2 , Tiago J. L. Silva 1 , M. H. Garcia 1 , M. P. Robalo 3 1 FCUL, Campo Grande, 1049-001 Lisboa, Portugal 2 Centro de Química de Évora, R. Romão Ramalho 59, 7000-671 Évora, Portugal 3 ADEQ/ISEL, R. Conselheiro Emídio Navarro, 1, 1959-007 Lisboa margaridaggs@gmail.com Organometallic compounds continue to attract considerable interest owing to their application in the field of nonlinear optics (NLO) [1]. For second-order nonlinear optics, strongly asymmetric systems are needed, which led to the development of typical push pull systems in which the metal centre, bound to a highly polarizable conjugated backbone, acts as an electron donor (D) or acceptor (A) group. This is the case of the 5 -monocyclopentadienylmetal complexes presenting benzene- or thiophene-based conjugated ligands coordinated to the metal centre through nitrile or acetylide linkages which revealed to be much more efficient donor groups for secondorder NLO purposes than the traditional organic donor groups [2,3]. Recently, a new promising approach has emerged that is the concept of switchable second-order nonlinear optical (SONLO) properties [4]. This makes possible to achieve a switch in the SONLO response between two forms since they have great difference in the magnitude of the corresponding first hyperpolarizabilities. The hyperpolarizability can be altered, for instance, by reducing the donor capacity of the donor moiety (D) by oxidation. Thus, the presence of redox-active metal centers together with a hyperpolarizable conjugated framework provides good opportunities for modulation of molecular NLO responses, and is hence a primary justification for the study of these systems. The cyclic voltammetry (CV) plays a role in this field. Besides the information about the electron richness of redox-active centres and the correlation with spectroscopic properties, CV can give an insight on the reversibility/stability of oxidized and reduced species. In our ongoing work on the study of organometallic compounds with molecular 5 -monocyclopentadienyliron(II) and nickel(II) complexes with substituted thiophene-based ligands in view of the potential use of these systems as switchable SONLO molecules. Acknowledgments: We thank to COMPETE/F EDER for financial support (F COMP-01-0124- F EDER-007433). References [1] Goovaerts, E; Wenseleers W.; Garcia, M.H.; Cross G.H. Handbook of Advanced Electronic and Photonic Materials, Ed. H.S. Nalwa, 2001, 9, 127. [2] Powell, C.M.; Humphrey, M. G. Coord. Chem. Rev. 2004, 248, 725. [3] Garcia, M.H.; Mendes, P. J.; Robalo, M.P.; Duarte, M.T.; Lopes, N. J. Organomet. Chem. 2009, 694, 2888. [4] Asselberghs, I.; Clays, K.; Persoons, A; Ward M.; McCleverty, J. J. Mater. Chem. 2004, 14, 2831. September, 811, 2010. ISEL - Lisbon 95
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