Chemistry Department, Marquette University, P.O. Box 1881, Milwaukee, WI 53092, USA.
Molecules. 2020 Jan 12;25(2):303. doi: 10.3390/molecules25020303.
Understanding the solvation and ion-pairing interactions of anionic substrates in room-temperature ionic liquids (RTIL) is key for the electrochemical applications of these new classes of solvents. In this work, cyclic voltammetry and visible and infrared spectroelectrochemistry of tetracyanoquinodimethane (TCNQ) was examined in molecular (acetonitrile) and RTIL solvents, as well as mixtures of these solvents. The overall results were consistent with the formation of RTIL/acetonitrile nanodomains. The voltammetry indicated that the first electrogenerated product, TCNQ, was not incorporated into the RTIL nanodomain, while the second electrogenerated product, TCNQ, was strongly attracted to the RTIL nanodomain. The visible spectroelectrochemistry was also consistent with these observations. Infrared spectroelectrochemistry showed no discrete ion pairing between the cation and TCNQ in either the acetonitrile or RTIL solutions. Discrete ion pairing was, however, observed in the acetonitrile domain between the tetrabutylammonium ion and TCNQ. On the other hand, no discrete ion pairing was observed in BMImPF or BMImBF solutions with TCNQ. In BMImNTf, however, discrete ion pairs were formed with BMIm and TCNQ. Density function theory (DFT) calculations showed that the cations paired above and below the aromatic ring. The results of this work support the understanding of the redox chemistry in RTIL solutions.
了解室温离子液体 (RTIL) 中阴离子底物的溶剂化和离子对相互作用对于这些新型溶剂的电化学应用至关重要。在这项工作中，研究了四氰基醌二甲烷 (TCNQ) 在分子 (乙腈) 和 RTIL 溶剂以及这些溶剂的混合物中的循环伏安法和可见及红外光谱电化学。总体结果与 RTIL/乙腈纳米域的形成一致。伏安法表明，第一个电生成的产物 TCNQ 没有掺入 RTIL 纳米域，而第二个电生成的产物 TCNQ 强烈地被吸引到 RTIL 纳米域中。可见光谱电化学也与这些观察结果一致。红外光谱电化学表明，在乙腈或 RTIL 溶液中，阳离子和 TCNQ 之间没有离散的离子对。然而，在乙腈域中，四丁基铵离子和 TCNQ 之间观察到离散的离子对。另一方面，在 BMImPF 或 BMImBF 与 TCNQ 的溶液中没有观察到离散的离子对。然而，在 BMImNTf 中，形成了离散的离子对，其中包括 BMIm 和 TCNQ。密度泛函理论 (DFT) 计算表明，阳离子在芳环上方和下方配对。这项工作的结果支持对 RTIL 溶液中氧化还原化学的理解。
