KU Leuven, Department of Chemistry, Celestijnenlaan 200F - P.O. Box 2404, B-3001 Heverlee, Belgium.
Dalton Trans. 2014 Jan 28;43(4):1589-98. doi: 10.1039/c3dt52416g.
New cationic silver-containing ionic liquids were synthesized and used as non-aqueous electrolytes for the electrodeposition of silver layers. In the liquid state of these ionic liquids, a silver (i) cation is coordinated by pyridine-N-oxide (py-O) ligands in a 1 : 3 metal-to-ligand ratio, although in some cases a different stoichiometry of the silver center crystallized out. As anions, bis(trifluoromethanesulfonyl)imide (Tf2N), trifluoromethanesulfonate (OTf), methanesulfonate (OMs) and nitrate were used, yielding compounds with the formulae [Ag(py-O)3][Tf2N], [Ag(py-O)3][OTf], [Ag(py-O)3][OMs] and [Ag(py-O)3][NO3], respectively. The compounds were characterized by CHN analysis, FTIR, NMR, DSC, TGA and the electrodeposition of silver was investigated by cyclic voltammetry, linear potential scans, scanning electron microscopy (SEM) and energy-dispersive X-ray spectrometry (EDX). With the exception of [Ag(py-O)3][Tf2N], which melts at 108 °C, all the silver(i) compounds have a melting point below 80 °C and were tested as electrolytes for silver electrodeposition. Interestingly, very high current densities were observed at a potential of -0.5 V vs. Ag/Ag(+) for the compounds with fluorine-free anions, i.e. [Ag(py-O)3][NO3] (current density of -10 A dm(-2)) and [Ag(py-O)3][OMs] (-6.5 A dm(-2)). The maximum current density of the compound with the fluorinated anion trifluoromethanesulfonate, [Ag(py-O)3][OTf], was much lower: -2.5 A dm(-2) at -0.5 V vs. Ag/Ag(+). Addition of an excess of ligand to [Ag(py-O)3][OTf] resulted in the formation of the room-temperature ionic liquid [Ag(py-O)6][OTf]. A current density of -5 A dm(-2) was observed at -0.5 V vs. Ag/Ag(+) for this low viscous silver salt. The crystal structures of several silver complexes could be determined by X-ray diffraction, and it was found that several of them had a stoichiometry different from the 1 : 3 metal-to-ligand ratio used in their synthesis. This indicates that the compounds form crystals with a composition different from that of the molten state. The electrochemical properties were measured in the liquid state, where the metal-to-ligand ratio was 1 : 3. Single crystal X-ray diffraction measurements showed that silver(i) is six coordinate in [Ag(py-O)3][Tf2N] and [Ag(py-O)3][OTf], while it is five coordinate in the other complexes. In [Ag3(py-O)8][OTf]3, there are two different coordination environments for silver ions: six coordinate central silver ions and five coordinate for the outer silver ions. In some of the silver(i) complexes, silver-silver interactions were observed in the solid state.
新的阳离子含银离子液体被合成并用作电沉积银层的非水电解液。在这些离子液体的液态状态下，银（i）阳离子与吡啶-N-氧化物（py-O）配体配位，配位比为 1：3，尽管在某些情况下，结晶出的银中心具有不同的化学计量比。作为阴离子，使用双（三氟甲烷磺酰基）亚胺（Tf2N）、三氟甲烷磺酸盐（OTf）、甲烷磺酸盐（OMs）和硝酸盐，得到化学式分别为[Ag（py-O）3][Tf2N]、[Ag（py-O）3][OTf]、[Ag（py-O）3][OMs]和[Ag（py-O）3][NO3]的化合物。这些化合物通过 CHN 分析、FTIR、NMR、DSC、TGA 进行了表征，并通过循环伏安法、线性电位扫描、扫描电子显微镜（SEM）和能谱（EDX）研究了银的电沉积。除了熔点为 108°C 的[Ag（py-O）3][Tf2N]之外，所有的银（i）化合物的熔点都低于 80°C，并且被测试为银电沉积的电解液。有趣的是，对于无氟阴离子的化合物[Ag（py-O）3][NO3]（电流密度为-10 A dm-2）和[Ag（py-O）3][OMs]（-6.5 A dm-2），在-0.5 V 相对于 Ag/Ag(+)的电位下观察到非常高的电流密度。具有氟化阴离子三氟甲烷磺酸盐的化合物[Ag（py-O）3][OTf]的最大电流密度要低得多：-0.5 V 相对于 Ag/Ag(+)时为-2.5 A dm-2。向[Ag（py-O）3][OTf]中加入过量的配体，得到室温离子液体[Ag（py-O）6][OTf]。在-0.5 V 相对于 Ag/Ag(+)的电位下，观察到这种低粘性银盐的电流密度为-5 A dm-2。通过 X 射线衍射确定了几种银配合物的晶体结构，发现其中几种的化学计量比与合成中使用的 1：3 金属与配体比不同。这表明这些化合物形成的晶体与熔融状态的组成不同。在液态下测量了电化学性质，其中金属与配体的比例为 1：3。单晶 X 射线衍射测量表明，银（i）在[Ag（py-O）3][Tf2N]和[Ag（py-O）3][OTf]中为六配位，而在其他配合物中为五配位。在[Ag3（py-O）8][OTf]3 中，银离子有两种不同的配位环境：中心银离子为六配位，外部银离子为五配位。在一些银（i）配合物中，在固态中观察到银-银相互作用。
