Electrochemically Directed Synthesis of Co2+ and Ni2+ Complexes with TCNQF42– (TCNQF4 = 2,3,5,6‐Tetrafluoro‐7,7,8,8‐tetracyanoquinodimethane)

Abstract

AbstractThe electrocrystallization of transition metal coordination polymers MTCNQF4 containing TCNQF42– dianions and M2+ cations (TCNQF4 = 2,3,5,6‐tetrafluoro‐7,7,8,8‐tetracyanoquinodimethane, M = Co or Ni) has been achieved in acetonitrile (0.1 M Bu4NPF6) at glassy carbon and indium tin oxide electrodes and the reaction pathway monitored by cyclic voltammetry and surface plasmon resonance. TCNQF4 is sequentially reduced to TCNQF4·– and then TCNQF42–. In the presence of M2+, the TCNQF42– formation is accompanied by the electrocrystallization of the sparingly soluble MTCNQF4 on the electrode surface. Cyclic voltammetry studies reveal that two phases of MTCNQF4 are formed. One is kinetically favoured and rapidly converts to a second thermodynamically stable phase. The formation of MTCNQF4 is possible because of the relatively high solubility of M(TCNQF4)2 derivatives. The solubilities of CoTCNQF4 and NiTCNQF4 are 8.6 × 10–6 and 9.2 × 10–6 M, respectively, in neat acetonitrile and 2.2 × 10–5 and 2.4 × 10–5 M, respectively, in an acetonitrile solution containing Bu4NPF6 (0.1 M). The presence of TCNQF42– dianions rather than TCNQF4·– monoanions in the coordination polymers was confirmed by UV/Vis, IR and Raman spectroscopy. Scanning electron microscopy images show that the morphology of the electrocrystallized MTCNQF4 depends on the applied potential for CoTCNQF4, but not for the NiTCNQF4 complex.