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 09 Redox behavior of dinuclear iron(II) and ruthenium(II) complexes as potential molecular wires A. Catarina Sousa 1 , Vanda Pacheco 1 , M. Paula Robalo 1,2 1 Área Departamental de Engenharia Química, Instituto Superior de Engenharia de Lisboa, Instituto Politécnico de Lisboa, R. Conselheiro Emídio Navarro, 1, 1959-007, Lisboa, Portugal; 2 Centro de Química Estrutural, Complexo I, IST, Av. Rovisco Pais, 1049-01 Lisboa, Portugal acsousa@deq.isel.ipl.pt Molecular wires comprising mixed-valence bimetallic units or remote redox-active organometallic groups linked by conjugated bridging organic chains could be exploited in molecular electronics and optoelectronic devices 1 . e - Metal centre Organic spacer Metal centre Our recent work in this field has been the design and development of transition metal complexes, with a special emphasis on the half sandwich iron(II) and ruthenium(II) compounds, with nitrile or alkynyl organic ligands, which can be used as building blocks of molecular wires, allowing electronic communication between redox-active terminal end groups through delocalized bonds. Since the cyclic voltammetry can be used as a tool to evaluate the efficiency of this electronic interaction between the metal centres, we report in this communication, the electrochemical behavior of several mono and dinuclear iron(II) and ruthenium(II) -CH 2 - C- C(H)=C(H)- -C 6 H 4 - ([CpFe(dppe)] + , [CpFe(CO) 2 ] + , [CpRu(dppe)] + . The cyclic voltammograms of the studied compounds were performed in 1 x 10 -3 M dichloromethane and acetonitrile solutions, using tetrabutylammonium hexafluorophosphate (TBAPF 6 ) as supporting electrolyte (0.2 M) at different scan rates (20-1000 mV/s). The obtained results are discussed in terms of the electron richness of the metal centres and electronic properties of the organic ligands upon coordination, which can be related to the metal-to-ligand bonding ability. Furthermore, the ability of the different organic spacers in the electronic communication between the metal centres was also evaluated. Acknowledgements: We thank Fundação para a Ciência e a Tecnologia (F CT/MCTES) for partial financial support (project PTDC/QUIM/65379/2006) and IPL (project IPL/16/2003). References [1] a) Paul, F., Lapinte, C., Coord. Chem. Rev., 1998, 178-180, 431-509; b) Ceccon, A. Santi, S., Orian, L., Bisello, A., Coord. Chem. Rev., 2004, 248, 683-724. September, 811, 2010. ISEL - Lisbon 100
XII Iberian Meeting of Electrochemistry & XVI Meeting of the Portuguese Electrochemical Society PE 10 Investigation of 4-dimethoxymethyl- and 4-formyl-substituted 1,4-dihydropyridine redox reactions. Anna Lielpetere, Inguna Goba, Baiba Turovska Latvian Institute of Organic Synthesis, Aizkraukles 21, Riga, Latvia anna.lielpetere@gmail.com A little attention has yet been paid to the chemistry of formyl-substituted dihydropyridines [1,2] and there are no electrochemical investigations of them. In the work the synthesis and anodic oxidation of symmetrical and asymmetrical substituted 1,4-DHP bearing chemically active formyl- or its protective acetal group has been studied. In acetonitrile the anodic oxidation of H R H R X X Y X the studied compounds proceed in one irreversible step Figure 1, Figure 2. During the H C N C H H 3 3 3 C N C H 3 controlled potential electrolysis all studied H H compounds lost the substituent at C-4, while the X = C N, C O C H 3 , C O O C H 3 X = C O C H 3 , C O O C H 3 ; Y = C N products of their chemical oxidation R = C H(O C H 3 ) 2 , C H O R = C H(O C H 3 ) 2 , C H O (2,3-dicyano-5,6-dichloro-p-benzoquinone) were corresponding 4-substituted pyridines. N C H 3 C O H O C H 3 C H C O C H 3 -e H 3 C N C H 3 H H 3 C O O C H 3 H C H H N C C O C H 3 N C C O C H 3 . + + H 3 C N C H 3 H 3 C N C H 3 H Fig. 1. Anodic oxidation of 1,4-DHP Fig. 2. Anodic oxidation of 1,4-DHP in MeCN/0.1 M NaClO 4 in MeCN/0.1 M NaClO 4 H ClO 4 - N C H 3 C H . + N H O C H C O C H 3 .. .. C H 3 -e N C H 3 C H N H O C H C O C H 3 C H 3 H 3 C O O C H 3 H C H N C C O C H 3 .. H 3 C N C H 3 H N C H 3 C O H C H C O C H 3 .. N C H 3 H 4-Formyl-substituted 1,4-DHP are stable compounds at the room temperature, while in the solution aldehyde group at C-4 in dihydropyridine molecule could easy be oxidized to the acid or reduced with subsequent intramolecular condensation with the substituent at C-3 or C-5. Acknowledgments: We are grateful to the Latvian Science Foundation (Grant 2010_09.1558) for their support of this research. References [1] Grau M. A., Illescas B., Martinez Torres M. L., Fernandez-Gadea J., Martin N. Tetrahedron Letters, 2002, 43, 4133. [2] Li A. H., Moro S., Melman N., Ji X. D., Jacobson K. A. J. Med. Chem., 1998, 41, 3186. September, 811, 2010. ISEL - Lisbon 101
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