MethodsAll chemicals purchased were of reagent grade and used without further purification.[Ag(MeCN)][Tf 2 N] was synthesised as previously described [S1]. TGA studies were performed on a TA instruments Q600 thermogravimeter. The temperature was scanned from room temperature up to 400 °C at a heating rate of 5 °C per minute. Elemental analyses (C, H, N) were carried out using a CE Instruments EA-1110 elemental analyser. The IR and Raman spectra were recorded on a Bruker Vertex 70 FTIR spectrometer, coupled with a Ram II Raman module, at a resolution of 4 cm -1 . Melting points were determined on a Mettler-Toledo 822 DSC instrument at a heating rate of 10 °C per minute. Viscosities have been measured on a Brookfield cone plate viscosimeter (LVDV-II + Programmable Viscometer) with a cone spindle CPE-40. The ionic liquid was kept under a dry nitrogen atmosphere during the measurement and the temperature of the sample was controlled by a circulating water bath.The morphology and elemental composition of the silver deposits were determined by scanning electron microscopy (SEM) and energy-dispersive X-ray analysis (EDX) (Philips XL 30 FEG) and atomic force microscopy (AFM) (Digital Instruments Nanoscope III AFM).The electrochemical experiments were performed in an argon filled glove box with O 2 and H 2 O concentrations below 1 ppm. Gold-covered silicon wafers have been used as the substrates for electrodeposition. In order to make the current density uniform across the whole electrode area, the electrode was recessed by placing it inside a PTFE-sample holder, whichElectronic Supplementary Material (ESI) for Dalton Transactions This journal is
New metal-containing ionic liquids [Cu(CH(3)CN)(n)][Tf(2)N] (n=2, 4; Tf(2)N=bis(trifluoromethylsulfonyl)- amide) have been synthesised and used as a non-aqueous electrolyte for the electrodeposition of copper at current densities greater than 25 A dm(-2). The tetrahedral copper(I)-containing cation in [Cu(CH(3)CN)(4)][Tf(2)N] is structurally analogous to quaternary ammonium and phosphonium ionic liquids and overcomes problems of metal solubility and mass transport. Two CH(3)CN ligands are removed at elevated temperatures to give [Cu(CH(3)CN)(2)][Tf(2)N], which can be used as a concentrated non-aqueous electrolyte. The structural and electrochemical characterisation of these compounds is described herein.
A series of nitrile-functionalized ionic liquids were found to exhibit temperature-dependent miscibility (thermomorphism) with the lower alcohols. Their coordinating abilities toward cobalt(II) ions were investigated through the dissolution process of cobalt(II) bis(trifluoromethylsulfonyl)imide and were found to depend on the donor abilities of the nitrile group. The crystal structures of the cobalt(II) solvates [Co(C(1)C(1CN)Pyr)(2)(Tf(2)N)(4)] and [Co(C(1)C(2CN)Pyr)(6)][Tf(2)N](8), which were isolated from ionic-liquid solutions, gave an insight into the coordination chemistry of functionalized ionic liquids. Smooth layers of cobalt metal could be obtained by electrodeposition of the cobalt-containing ionic liquids.
Liquid metal salts are electrolytes with the highest possible metal concentration for electrodeposition, because the metal ion is an integral part of the solvent. This paper introduces the new ionic silver complexes [Ag(MeCN)(4)](2)[Ag(Tf(2)N)(3)], [Ag(MeCN)][Tf(2)N] and [Ag(EtIm)(2)][Tf(2)N], where MeCN stands for acetonitrile, EtIm for 1-ethylimidazole and Tf(2)N is bis(trifluoromethylsulfonyl)imide. These complexes have been characterized by differential scanning calorimetry, single crystal X-ray crystallography, thermogravimetrical analysis, Raman spectroscopy and cyclic voltammetry. [Ag(MeCN)(4)](2)[Ag(Tf(2)N)(3)] is a room temperature ionic liquid. Smooth silver layers of good quality could be deposited from it, at current densities of up to 25 A dm(-2) in unstirred solutions. [Ag(EtIm)(2)][Tf(2)N] melts at 65 °C and can be used as an electrolyte for silver deposition above this temperature. [Ag(MeCN)][Tf(2)N] has a melting point that is too high to be useful in electrodeposition. Addition of thiourea or 1H-benzotriazole to the electrolyte decreased the surface roughness of the silver coatings. The morphology of the metal layers was investigated by atomic force microscopy (AFM). Adsorption of 1H-benzotriazole on the silver metal surface has been proven by Raman spectroscopy. This work shows the usefulness of additives in improving the quality of metal films electrodeposited from ionic liquids.
The electrochemical behavior of the low-melting copper salts ͓Cu͑MeCN͒ x ͔͓Tf 2 N͔ and ͓Cu͑PhCN͒ x ͔͓Tf 2 N͔ ͑x = 2-4͒, where MeCN is acetonitrile and PhCN is benzonitrile, is presented. In these compounds, the copper͑I͒ ion is a main component of the ionic liquid cation. Consequently, the copper concentration is the highest achievable for an ionic liquid and this permits to obtain a good mass transport and high current densities for electrodeposition. The cathodic limit of the ionic liquid is the reduction of copper͑I͒ to copper metal instead of the breakdown of the cation as in conventional ionic liquids. It is shown that pure, crack-free copper layers can be deposited from these copper-containing ionic liquids in unstirred solutions at current densities up to 25 A dm −2 .Ionic liquids are useful solvents for electrochemical applications because of their wide electrochemical window and the presence of intrinsic ionic charge carriers. 1-3 Examples of such applications are their use as electrolytes in batteries, in photovoltaic devices, and for the electrodeposition of metals. In all of these applications, good mass transfer is needed. However, as the viscosity of most ionic liquids is much higher than that of the most molecular solvents, the mass transport in ionic liquids is rather poor. Moreover, the mass transport is limited even further by the poor solubility of simple metal salts ͑e.g., chlorides͒ in most ionic liquids suitable for electrodeposition, except for the dicyanamide ionic liquids. 4-7 The limited solubility is due to the poor coordinating power of anions such as ͓BF 4 ͔ − , ͓PF 6 ͔ − , or bis͑trifluoromethyl-sulfonyl͒imide ͓͑Tf 2 N͔ − ͒.To increase the solubility, functionalized ionic liquids can be used. These ionic liquids have a built-in coordinating unit such as a nitrile group which can complex the metal ion, thereby increasing its solubility. 8,9 Another way to improve the solubility of metal ions in ionic liquids is to design ionic liquids with a metal complex as part of their composition. 10
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