Electrochemical synthesis and characterization of semiconducting Ni(TCNQF4)2(H2O)2 (TCNQF4=2,3,5,6-tetrafluoro-7,7,8,8-tetracyanoquinodimethane)

Thanh Hai Le, Ayman Nafady, Jinzhen Lu, Germanas Peleckis, Alan Maxwell Bond, Lisandra Lorraine Martin

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An electrochemical technique has been used to synthesize Ni(TCNQF4)2(H2O)2 (TCNQF4 = 2,3,5,6-tetrafluoro-7,7,8,8-tetracyanoquinodimethane). The method involves the reduction of solid TCNQF4 immobilized on an electrode surface in contact with Ni2+ (aq.)-containing electrolyte. The electrochemically irreversible, but chemically reversiblesolid–solid TCNQF4/Ni(TCNQF4)2(H2O)2 interconversion process is governed by nucleation and growth kinetics and is represented by the overall reaction: 2TCNQF4 (s, electrode) + Ni2+ (aq.) + 2H2O + 2e [rlhar2] Ni(TCNQF4)2(H2O)2 (s, electrode). Thus, the formation of Ni(TCNQF4)2(H2O)2 involves the one-electron reduction of TCNQF4 to [TCNQF4]·– coupled with an ingress of Ni2+ (aq.) from the aqueous electrolyte, while the reverse scan represents the oxidation of [TCNQF4]·– to TCNQF4 coupled with the egress of Ni2+ (aq.). Cyclic voltammograms for the TCNQF4/Ni(TCNQF4)2(H2O)2 solid–solid phase transformation are independent of the electrode material and the identity of the Ni2+ (aq.) counteranion but are strongly dependent on the concentration of Ni2+ (aq.) and the scan rate. UV/Vis, infrared, and Raman spectra confirm the presence of [TCNQF4]·– in the newly synthesized material. The composition of Ni(TCNQF4)2(H2O)2 was deduced from thermogravimetric and elemental analyses. Scanning electron microscopic images of Ni(TCNQF4)2(H2O)2 electrocrystallized onto the surface of an indium tin oxide electrode show a thin film morphology. Magnetic and conductivity data demonstrate that the complex behaves as a classical paramagnet and is a typical semiconductor with a band gap close to that of an insulator.
Original languageEnglish
Pages (from-to)2889 - 2897
Number of pages9
JournalEuropean Journal of Inorganic Chemistry
Issue number17
Publication statusPublished - 2012

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