The electrochemistry of simple inorganic molecules in room temperature ionic liquids

Abstract

A eletroquímica de compostos inorgânicos simples em líquidos iônicos a temperatura ambiente (RTIL) é revisada e alguns trabalhos novos nesta área são apresentados. Este artigo focaliza a comparação entre o comportamento eletroquímico em RTILs e em solventes apróticos convencionais. Alguns compostos (iodetos, O 2 , NO 2 , SO 2 , NH 3 ) apresentam reações e mecanismos similares em RTILs e em solventes apróticos (como é observado para compostos orgânicos). Entretanto, outras espécies (nitratos, PCl 3 , POCl 3 ) mostram comportamento excepcionalmente diferente em relação aos solventes tradicionais. Isto torna os RTILs um meio promissor para o estudo de compostos inorgânicos, e destaca a necessidade de maiores investigações nesta área.The electrochemistry of simple inorganic compounds in room temperature ionic liquids (RTILs) is reviewed and some new work in this area is presented. This paper focuses on the comparison between electrochemical behaviour in RTILs and in conventional aprotic solvents. Some compounds (iodides, O 2 , NO 2 , SO 2 , NH 3 ) display similar reactions and mechanisms in RTILs as in aprotic solvents (as is observed for organic compounds). However other species (nitrates, PCl 3 , POCl 3 ) show remarkably different behaviour to traditional solvents. This makes RTILs very promising media for the study of inorganic compounds, and highlights the need for more investigations in this exciting area.

Ionic liquids: Electrochemical investigation on corrosion activity of ethyl-dimethyl-propylammonium bis(trifluoromethylsulfonyl)imide at high temperature

“…D ox remains in the range of 10 -10 m 2 s -1 upto 403 K, the same order found in literature [23,24,27] for lower temperatures. Around 443 K, the diffusion coef ficient rises up to 7.00 × 10 -9 m 2 s -1 but further data on oxygen diffusion coefficients are not available in liter ature for the studied ionic liquid or similar in this range of temperatures.…”

The electrochemical reduction of the purines guanine and adenine at platinum electrodes in several room temperature ionic liquids

“…4, reduction of guanine in [P 14,6,6,6 ][FAP] presents a well defined peak (I) at −1.65 V vs Fc/Fc + redox couple. These values suggest that guanine is more easily reduced in this ionic liquid than in [N 6,2,2,2 ][N(Tf) 2 ] (E pc = −1.86 V vs Fc/Fc + ), probably due to the greater ease of proton abstraction from [P 14,6,6,6 ] + compared to [N 6,2,2,2 ] + .…”

“…This indicates that the anion radical is less stable in [P 14,6,6,6 ][N(Tf) 2 ] than in [N 6,2,2,2 ][N(Tf) 2 ]. As the scan rate increases up to 5000 mV s −1 , the ratio of I pa /I pc peak heights increases; behaviour typical of an electrodic process with a subsequent chemical reaction [36].…”

“…As verified previously, the oxidation peak current is smaller at low guanine concentrations, increasing with increasing concentration, consistent with the mechanism involving dimerization of the anion radical. A faster dimerizaton rate constant of 8.5 × 10 4 mol −1 L s −1 was obtained for the guanine radical anion in [P 14,6,6,6 ][FAP].…”

“…Ionic liquids (ILs) [11][12][13][14] have emerged as a novel non-aqueous, polar class of solvents that hold great promise in investigations of electrochemical mechanisms [15][16][17][18][19]. The wide electrochemical windows [16,20], intrinsic ion conductivity, high viscosity and hydrophobicity have shown that RTILs are suitable media for supporting reductive processes occurring at very negative potentials allowing stabilization of intermediates in some cases, and improving solubility in others.…”