Electrochemical studies of the bis (triphenyl phosphine) ruthenium(II) complex, cis -[RuCl2(L)(PPh3)2], with L = 2-(2′-pyridyl)quinoxaline

Abstract

Electrochemical studies of the newly synthesized bis(triphenyl phosphine) ruthenium(II) complex, cis-[RuCl2(L)(PPh3)2] (1, with L = 2-(2′-pyridyl)quinoxaline, C13N3H9), were performed in acetonitrile (ACN). For this purpose, cyclic voltammograms (CVs) as well as electrochemical impedance spectra (EIS) were recorded on either glassy carbon (GC), platinum (Pt), gold (Au), or multi-walled carbon nanotube (MWCNT) electrodes. Qualitative examination of solutions of 1 in ACN was performed on the basis of conductivity measurements and electrospray ionization mass spectrometry (ESI–MS). The conductivity data suggest that 1 is a 1 : 1 type electrolyte in ACN. The ESI spectra further demonstrate that upon dissolution of 1 in ACN progressive replacement of chloro- and PPh3-ligands by ACN occurs, leading to formation of [RuCl(L)(PPh3)(CH3CN)2]+Cl−, [2 + Cl − ]. The CVs recorded for [2 + Cl − ] on various working electrodes demonstrate that the reversibility of the redox couple 22 +/+ enhances with the order: Au < Pt < MWCNT < GC. The EI spectra verify that GC and MWCNT electrodes provide insignificant barrier for interfacial electron transfer since they afford less charge-transfer resistance.