A new method for electrocrystallization of AgTCNQF4 and Ag2TCNQF4 (TCNQF4= 2,3,5,6-tetrafluoro-7,7,8,8-tetracyanoquinodimethane) in acetonitrile

Thanh Le, Anthony O'Mullane, Lisandra Martin, Alan Bond

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20 Citations (Scopus)

Abstract

Semiconducting AgTCNQF(4) (TCNQF(4) = 2,3,5,6-tetrafluoro-7,7,8,8-tetracyanoquinodimethane) has been electrocrystallized from an acetonitrile (0.1 M Bu(4)NPF(6)) solution containing TCNQF(4) and Ag(MeCN) (4) (+) . Reduction of TCNQF(4) to the TCNQF (4) (1-) anion, followed by reaction with Ag(MeCN) (4) (+) forms crystalline AgTCNQF(4) on the electrode surface. Electrochemical synthesis is simplified by the reduction of TCNQF(4) prior to Ag(MeCN) (4) (+) compared with the analogous reaction of the parent TCNQ to form AgTCNQ, where these two processes are coincident. Cyclic voltammetry and surface plasmon resonance studies reveal that the electrocrystallization process is slow on the voltammetric time scale (scan rate = 20 mV s(-1)) for AgTCNQF(4), as it requires its solubility product to be exceeded. The solubility of AgTCNQF(4) is higher in the presence of 0.1 M Bu(4)NPF(6) supporting electrolyte than in pure solvent. Cyclic voltammetry illustrates a dependence of the reduction peak potential of Ag(MeCN) (4) (+) to metallic Ag on the electrode material with the ease of reduction following the order Au <Pt <GC <ITO. Ultraviolet-visible, Fourier transform infrared, and Raman spectra confirmed the formation of reduced TCNQF (4) (1-) and optical microscopy showed needle-shaped morphology for the electrocrystallized AgTCNQF(4). AgTCNQF(4) also can be formed by solid-solid transformation at a TCNQF(4)-modified electrode in contact with aqueous media containing Ag(+) ions. Chemically and electrochemically synthesized AgTCNQF(4) are spectroscopically identical. Electrocrystallization of Ag(2)TCNQF(4) was also investigated; however, this was found to be thermodynamically unstable and readily decomposed to form AgTCNQF(4) and metallic Ag, as does chemically synthesized Ag(2)TCNQF(4).
Original languageEnglish
Pages (from-to)2293 - 2304
Number of pages12
JournalJournal of Solid State Electrochemistry
Volume15
Issue number11
DOIs
Publication statusPublished - 2011

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