Electrochemical Synthesis and Characterization of Semiconducting Ni(TCNQF 4 ) 2 (H 2 O) 2 (TCNQF 4 = 2,3,5,6‐tetrafluoro‐7,7,8,8‐tetracyanoquinodimethane)

An electrochemical technique has been used to synthesize Ni(TCNQF 4 ) 2 (H 2 O) 2 (TCNQF 4 = 2,3,5,6‐tetrafluoro‐7,7,8,8‐tetracyanoquinodimethane). The method involves the reduction of solid TCNQF 4 immobilized on an electrode surface in contact with Ni 2+  (aq.)‐containing electrolyte. The electrochemically irreversible, but chemically reversiblesolid–solid TCNQF 4 /Ni(TCNQF 4 ) 2 (H 2 O) 2 interconversion process is governed by nucleation and growth kinetics and is represented by the overall reaction: 2TCNQF 4  (s, electrode) + Ni 2+  (aq.) + 2H 2 O + 2e [rlhar2] Ni(TCNQF 4 ) 2 (H 2 O) 2  (s, electrode). Thus, the formation of Ni(TCNQF 4 ) 2 (H 2 O) 2 involves the one‐electron reduction of TCNQF 4 to [TCNQF 4 ] · – coupled with an ingress of Ni 2+  (aq.) from the aqueous electrolyte, while the reverse scan represents the oxidation of [TCNQF 4 ] · – to TCNQF 4 coupled with the egress of Ni 2+  (aq.). Cyclic voltammograms for the TCNQF 4 /Ni(TCNQF 4 ) 2 (H 2 O) 2 solid–solid phase transformation are independent of the electrode material and the identity of the Ni 2+  (aq.) counteranion but are strongly dependent on the concentration of Ni 2+  (aq.) and the scan rate. UV/Vis, infrared, and Raman spectra confirm the presence of [TCNQF 4 ] · – in the newly synthesized material. The composition of Ni(TCNQF 4 ) 2 (H 2 O) 2 was deduced from thermogravimetric and elemental analyses. Scanning electron microscopic images of Ni(TCNQF 4 ) 2 (H 2 O) 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.