Electrochemically directed synthesis of Cu2I(TCNQF4II-)(MeCN)2 (TCNQF 4 = 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

Abstract

The new compound Cu2I(TCNQF4II-)(MeCN)2 (TCNQF42- = dianion of 2,3,5,6-tetrafluoro-7,7,8,8-tetracyanoquinodimethane) has been synthesized by electrochemically directed synthesis involving reduction of TCNQF4 to TCNQF42- in acetonitrile containing [Cu(MeCN) 4]+(MeCN) and 0.1 M Bu4NPF 6. In one scenario, TCNQF42- is quantitatively formed by reductive electrolysis of TCNQF4 followed by addition of [Cu(MeCN)4]+ to form the Cu2I(TCNQF4II-)(MeCN)2 coordination polymer. In a second scenario, TCNQF4 is reduced in situ at the electrode surface to TCNQF42-, followed by reaction with the [Cu(MeCN)4]+ present in the solution, to electrocrystallize Cu2I(TCNQF4II-)(MeCN)2. Two distinct phases of Cu2I(TCNQF4II-)(MeCN)2 are formed in this scenario; the kinetically favored form being rapidly converted to the thermodynamically favored Cu2I(TCNQF4II-)(MeCN)2. The postulated mechanism is supported by simulations. The known compound CuITCNQF4I- also has been isolated by one electron reduction of TCNQF4 and reaction with [Cu(MeCN)4]+. The solubility of both TCNQF42-- and TCNQF4•--derived solids indicates that the higher solubility of CuITCNQF 4I- prevents its precipitation, and thus Cu 2I(TCNQF4II-)(MeCN)2 is formed. UV-visible and vibrational spectroscopies were used to characterize the materials. Cu2I(TCNQF4II-)(MeCN) 2 can be photochemically transformed to CuITCNQF 4I- and Cu0. Scanning electron microscopy images reveal that CuITCNQF4I- and Cu 2I(TCNQF4II-)(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 Cu2I(TCNQF4II-)(EtCN)2 analogue shows that this compound is structurally related to Cu2I(TCNQF4II-)(MeCN)2. © 2014 American Chemical Society.