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UV-visible spectroelectrochemical study of some para- and ortho-benzoquinoid compounds: comparative evaluation of their electrochromic properties

1989; Elsevier BV; Volume: 260; Issue: 1 Linguagem: Inglês

10.1016/0022-0728(89)87100-1

2590-2954

A. Desbène‐Monvernay, P.C. Lacaze, A. Cherigui,

Conducting polymers and applications

Several para-benzoquinones [chloranil (p-CA), fluoranil (p-FA), dichloro-dicyano-benzoquinone (p-DDQ), benzoquinone (p-BQ)] and ortho-benzoquinones [chloranil (o-CA), bromanil (o-BA)] were studied in CH3CN + NaClO4 medium by UV-visible spectroelectrochemistry in order to estimate their electrochromic properties. Of all the p-quinones studied, only p-BQ gave a coloured film which adhered to the electrode surface. However, the optical contrast between the reduced and the neutral forms weakened rapidly after several cyclic potential scans. The other p-quinones gave only a coloration which diffused into the solution and are therefore not suitable as electrochromic materials. Electrochromic properties were found to be superior with o-quinones (o-CA and o-BA), and the best results obtained were observed with o-CA whose lifetime during permanent cycling was better than 105 cycles. The quinone films produced by electrochemical reduction were analysed by EPR, XPS and IR to verify that they were sodium salts of radical anions.