Scanning electrochemical microscopy study of the solid–solid interconversion of TCNQ to phase I and phase II CuTCNQ

The reduction of 7,7,8,8-tetracyanoquinodimethane (TCNQ) crystals attached to a glassy carbon electrode in the presence of Cu2+(aq) to form CuTCNQ(s) has been investigated using scanning electrochemical microscopy in the substrate generation tip collection mode and shown to involve a generation of soluble TCNQ−(aq). The subsequent oxidation of CuTCNQ does not involve simple expulsion of Cu+ into solution but a soluble complex attributed to Cu2+TCNQ−(aq). Mechanistic insights relative to the electrochemical conversion of CuTCNQ phase I into phase II by repetitive cycling of potential and electrochemical formation of KTCNQ have also been established.

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► SECM monitoring of solid–solid interconversion of TCNQ into CuTCNQ.
► Detection of soluble species in the inert zone between CuTCNQ formation and oxidation.
► Oxidation of CuTCNQ proceeds via formation of soluble Cu2+TCNQ−(aq) intermediate.
► SECM monitoring of electrochemically induced phase transformation of CuTCNQ.