resumo
The iron(III) mu-oxo bridged dimeric polyoxometalate [(PW11O39Fe)(2)O](10-) was isolated by reacting the transition metal monosubstituted Keggin anion [PW11O39Fe(H2O)](4-) and the ionic liquid 1-butyl-3-methylimidazolium bromide, (Bmim) Br, at pH 5.5. The crystal structure of (Bmim)(10)[(PW11O39Fe)(2)O]center dot 0.5H(2)O (1) (monoclinic, space group P2(1)/n, Z = 4) was determined by single crystal X-ray diffraction. By changing the reaction conditions, (Bmim)(4)[PW11O39Fe(H2O)]center dot H2O (2) was obtained, whilst the reaction between the Bmim(+) cation and the heteropolyanion [SiW11O39Fe(H2O](5-), in the pH conditions used for 1, afforded (Bmim)(5)[SiW11O39Fe(H2O)]center dot 4H(2)O (3). The compounds were characterized by spectroscopic techniques, thermal analysis, cyclic voltammetry, magnetic measurements and mass spectrometry. This study contributes to the understanding of iron mu-oxo dimer formation in polyoxometalate chemistry and calls attention to the influence of the counter-cations on the stability and formation of compound 1. The combination of the cationic part of ionic liquids and iron-substituted polyoxotungstates is predicted to lead to new materials with interest to catalysis, electrocatalysis and ionic liquid based nanocomposites.
palavras-chave
BRIDGED IRON(III) DIMERS; TEMPERATURE IONIC LIQUID; ELECTROCHEMICAL-BEHAVIOR; HYDROGEN-PEROXIDE; HETEROPOLYTUNGSTATE DIMER; ELECTROCATALYTIC ACTIVITY; PHOSPHOTUNGSTIC ACID; CATALYTIC-PROPERTIES; BENZENE OXIDATION; CRYSTAL-STRUCTURE
categoria
Chemistry
autores
Santos, FM; Brandao, P; Felix, V; Domingues, MRM; Amaral, JS; Amaral, VS; Nogueira, HIS; Cavaleiro, AMV
nossos autores
Ana Maria Vieira Silva Viana Cavaleiro
Professor Catedrático
Helena Isabel Seguro Nogueira
Professor Auxiliar com Agregação
João Cunha de Sequeira Amaral
Investigador Auxiliar
Paula Cristina Ferreira da Silva Brandão
Investigador Auxiliar
Vitor Brás Sequeira Amaral
Professor Catedrático
Vítor Félix
Professor Associado com AgregaçãoGrupos
G1 - Materiais Porosos e Nanossistemas
G2 - Materiais Fotónicos, Eletrónicos e Magnéticos
G6 - Materiais Virtuais e Inteligência Artificial
agradecimentos
Thanks are due to the University of Aveiro and CICECO for financial support of this work. F.M. Santos acknowledges FCT for his PhD grant SFRH/BD/40857/2007.