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Coordination Environment of Highly Concentrated Solutions of CuII in Ionic Liquids through a Multidisciplinary Approach

Authors

  • Dr. Stefano Caporali,

    1. Dipartimento di Chimica, Università di Firenze via della Lastruccia 3, 50019 Sesto Fiorentino (FI) (Italy)
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  • Prof. Cinzia Chiappe,

    Corresponding author
    1. Dipartimento di Chimica e Chimica Industriale, Università di Pisa via Bonanno 33, 56126 Pisa (Italy), Fax: (+39) 0502219660
    • Dipartimento di Chimica e Chimica Industriale, Università di Pisa via Bonanno 33, 56126 Pisa (Italy), Fax: (+39) 0502219660
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  • Dr. Tiziana Ghilardi,

    1. Dipartimento di Chimica e Chimica Industriale, Università di Pisa via Bonanno 33, 56126 Pisa (Italy), Fax: (+39) 0502219660
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  • Dr. Christian Silvio Pomelli,

    1. Dipartimento di Chimica e Chimica Industriale, Università di Pisa via Bonanno 33, 56126 Pisa (Italy), Fax: (+39) 0502219660
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  • Dr. Calogero Pinzino

    1. Consiglio Nazionale delle Ricerche, Istituto di Chimica dei Composti OrganoMetallici, Area della ricerca, via G. Moruzzi 1, 56124 Pisa (Italy)
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Abstract

The coordination environment around CuII in highly concentrated solutions of copper(II) salts (CuCl2 and Cu(Tf2N)2) in two pure ionic liquids bearing the same anion, namely, 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ([bmim][Tf2N]) and 1-butyl-3-methylimidazolium chloride ([bmim]Cl), is investigated by X-ray photoelectron spectroscopy (XPS), UV/Vis spectroscopy, EPR spectroscopy and DFT calculations. Moreover, the electrochemical behavior of these mixtures is studied. Whereas reversible reduction of CuII to copper metal can be observed in the 1:1 [bmim][Tf2N]:Cu(Tf2N)2 solution, 2:1 and 1:1 [bmim]Cl:CuCl2 mixtures showed one-electron reduction of CuII to CuI with formation of a permanent deposit of CuCl. XPS, UV/Vis and EPR spectra as well as DFT calculations suggest the formation in [bmim]Cl of dynamic coordination complexes arising from the interaction between CuCl2 and [bmim]+Cl . The two long-lived situations are probably trigonal and deformed tetrahedral copper(II) chloride coordination complexes ([CuCl3] and [CuCl4]2−, respectively).

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