Electrochemically Directed Synthesis of Cu2I(TCNQF4II-)(MeCN)2 (TCNQF4=2,3,5,6-Tetrafluoro-7,7,8,8-tetracyanoquinodimethane): Voltammetry, Simulations, Bulk Electrolysis, Spectroscopy, Photoactivity, and X-ray Crystal Structure of the Cu2I(TCNQF4II-)(EtCN)2 Analogue

The new compound Cu-2(I)(TCNQF(4)(II-))(MeCN)(2) (TCNQF(4)(2-) = dianion of 2,3,S,6-tetrafluoro-7,7,8,8-tetracyanoquinodimethane) has been synthesized by electrochemically directed synthesis involving reduction of TCNQF, to TCNQF(4)(2-) in acetonitrile containing [Cu(MeCN)(4)](+)((MeCN)) and 0.1 M Bu4NPF6. In one scenario, TCNQF(4)(2-) is quantitatively formed by reductive electrolysis of TCNQF(4) followed by addition of [Cu(MeCN)(4)](+) to form the Cu-2(I)(TCNQF(4)(II-))(MeCN)(2) coordination polymer. In a second scenario, TCNQF(4) is reduced in situ at the electrode surface to TCNQF(4)(2-), followed by reaction with the [Cu(MeCN)(4)](+) present in the solution, to electrocrystallize Cu-2(I)(TCNQF(4)(II-))(MeCN)(2). Two distinct phases of Cu-2(I)(TCNQF(4)(II-))(MeCN)(2) are formed in this scenario; the kinetically favored form being rapidly converted to the thermodynamically favored Cu-2(I)(TCNQF(4)(II-))(MeCN)(2). The postulated mechanism is supported by simulations. The known compound Cu(I)TCNQF(4)(I-) also has been isolated by one electron reduction of TCNQF(4) and reaction with [Cu(MeCN)(4)](+). The solubility of both TCNQF(4)(2-) and TCNQF(4)(center dot-) derived solids indicates that the higher solubility of Cu(I)TCNQF(4)(II-) prevents its precipitation, and thus Cu-2(I)(TCNQF(4)(II-))(MeCN)(2) is formed. UV-visible and vibrational spectroscopies were used to characterize the materials. Cu2I(TCNQF(4)(II-))(MeCN)(2) can be photochemically transformed to Cu(I)TCNQF(4)(I-) and Cu-0. Scanning electron microscopy images reveal that Cu(I)TCNQF, and Cu-2(I)(TCNQF(4)(II-))(MeCN)(2) are electrocrystallized with distinctly different morphologies. Thermogravimetric and elemental analysis data confirm the presence of CH3CN, and single-crystal X-ray diffraction data for the Cu-2(I)(TCNQF(4)(II-))(EtCN)(2) analogue shows that this compound is structurally related to Cu-2(I)(TCNQF(4)(II-))(MeCN)(2).