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 13 Electrochemical studies on luminescent bis-calix[4]arenebased poly(p-phenylene ethynylene) copolymers M. Paula Robalo, Hugo S. Pinto, Alexandra I. Costa, José V. Prata Área Departamental de Engenharia Química and Centro de Investigação de Engenharia Química e Biotecnologia, Instituto Superior de Engenharia de Lisboa, Instituto Politécnico de Lisboa, R. Conselheiro Emídio Navarro, 1, 1959-007, Lisboa, Portugal. mprobalo@deq.isel.ipl.pt Considerable research efforts have been directed in the last decade towards the development of a diversity of conjugated polymers with tailored electronic and photophysical properties, owing to their potential application in electroluminescent devices (EL), such as photovoltaic cells and polymer LEDs. Efficiency of EL devices is intimately related to the oxidation and reduction potentials of the emitting polymer layers and cyclic voltammetry (CV) is a powerful technique to evaluate this efficiency. In the present communication, we report on the electrochemical studies of several related poly(p-phenylene ethynylene) (p-PPE) copolymers: C A L I X-p-PPE [1], containing non-substituted phenylene ethynylene groups linking the bis-calix[4]arene units (1) and the same incorporating 2,5-dialkoxy-p-phenylene ethynylene linkers [2] with variable chain lengths (2a-c). Some structurally related monomers and model compounds were also studied (e.g. tetrapropyl-calix[4]arene, end-capped biscalix[4]arene and T BP-p-PPE) in order to correlate the redox processes found in the copolymers with the different structural components. The electrochemical data of the polymers and related model compounds was also used to determine the HOMO/LUMO energy levels as well their electrochemical bandgaps (E g EC ). III O O O O C 3 H 7 C 3 H 7 C 3 H 7 R 1 C 3 H 7 C 3 H C 7 3 H n 7 O O O O R 2 I II 1: R 1 = R 2 = H 2: R 1 = R 2 = OR 3 a R 3 = OCH 2 CH 2 CH 3 b R 3 = OCH 2 (CH 2 ) 4 CH 3 c R 3 = OCH 2 (CH 2 ) 8 CH 3 2,5 2 1,5 1 0,5 0 E vs SCE (V) -‐0,5 -‐1 -‐1,5 Figure 1 Cyclic voltammogram for C A L I X-p-PPE (1) in dichloromethane at 100 mV.s -1 . -‐2 Acknowledgments: We thank Fundação para a Ciência e a Tecnologia/MCTES for partial financial support (project PTDC/QUIM/66663/2006). A. I. Costa thanks Instituto Superior de Engenharia de Lisboa for a doctoral fellowship.. References [1] Costa, A. I.; Ferreira, L.F.V.; Prata, J.V., J. Polym. Sci. Part A: Polym. Chem., 2008, 46, 6477. [2] Pinto, H.S., MSc thesis, ISEL, 2010. September, 811, 2010. ISEL - Lisbon 104
XII Iberian Meeting of Electrochemistry & XVI Meeting of the Portuguese Electrochemical Society PE 14 Ruthenium(II) and Iron(II) Complexes bearing low band-gap thiophenic ligands as possible N L O switches Tiago J. L. Silva 1 , Paulo J. G. Mendes 2 , M. Helena Garcia 1 , M. Paula Robalo 3 1 Faculdade de Ciências, Universidade de Lisboa, Campo Grande, 1749-001 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 tjsilva@fc.ul.pt Over the past decade, there was growth of interest in discovering new conducting molecules due to their potential applications in electrochromic devices, sensors, OLED's and more recently molecular switches. Non-Linear Optics (NLO) phenomenons, namely Second-Harmonic Generation (SHG), is one of the recently topics in molecular electrochemically changed in or switch, upon a redox process. Monocyclopentadienyliron (II) and ruthenium (II) complexes, combined with thiophene ues and have been widely studied for NLO [2]. Regarding the switching properties, oxidation in the transition metal, from M (II) to M (III) (M=Fe, Ru), can drastically reduce the NLO properties of these molecules and therefore it provides a way to electrochemically onoff In this communication, monocyclopentadienyliron (II) and ruthenium (II) complexes bearing thiophene ligands (Figure 1) with low band-gaps will be electrochemically tested as possible molecules for NLO switching. The electrochemical results will be correlated with spectroscopic data and the NLO properties predicted by DFT calculations, in order to anticipate the potentialities of the new compounds as molecular switches. Figure 1 Elucidating picture of the studied ruthenium complexes Acknowledgments: We thank to COMPETE/F EDER for financial support (F COMP-01-0124- F EDER-007433). References [1] Coe, Benjamin, Acc. Chem. Res., 2006, 39, 383 [2] a) Garcia, M. H., et al, J.Organomet. Chem., 2009, 694, 433. b) Mendes, P. et al, J. Mol. Struct.: THEOCHEM, 2010, 946, 33. c) Mendes, P. et al, J. Mol. Struct.: THEOCHEM, 2009, 900, 110. September, 811, 2010. ISEL - Lisbon 105
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