Solvent and electrolyte effects in enhancing the identification of intramolecular electronic communication in a multi redox-active diruthenium tetraferrocenoate complex, a triple-sandwiched dicadmium phthalocyanine and a ruthenocene-containing β-diketone

Enhanced electrochemical resolution of anodic processes is possible in the presence of [N(nBu)4][B(C6F5)4], 1, as supporting electrolyte over that obtained in the presence of [N(nBu)4][PF6]. By changing the anion of the supporting electrolyte to a salt having [B(C6F5)4]−, anions, electrochemical processes of especially cationic analytes can benefit. Thus, the redox chemistry of 0.5 mmol dm−3 solutions of [Ru2(μ-FcCOO)4·(CH3CH2OH)2][PF6], 2, Fc = ferrocenyl, in CH2Cl2/[N(nBu)4][B(C6F5)4] were found to involve four well-resolved ferrocenyl-based electrochemical reversible redox processes as well as reduction of RuIII–RuII. At 1.0 mmol dm−3 concentrations of 2, or in the presence of [N(nBu)4][PF6], the four ferrocenyl processes coalesced into only two waves as a result of (Fc+)⋯(PF6-) ion paring. Seventeen of the possible 18 one-electron transfer processes of the biscadmium trisphthalocyaninato complex [Cd2{Pc(C6H13)8}3], 3, could be observed in THF/[N(nBu)4][B(C6F5)4], but the electrochemical window of CH2Cl2/[N(nBu)4][B(C6F5)4] only allowed detection of 15 of these processes. Although reduction processes were unaffected, THF solvation leading to species such as (3n+)(THF)x with 1 ⩽ n ⩽ 4 and x ⩾ 1 as well as ion pair formation of the type (3n+)⋯(PF6-) prevented good resolution of oxidation processes. The CH2Cl2/[N(nBu)4][B(C6F5)4] system also allowed detection of reversible one-electron transfer ferrocenyl (Fc/Fc+) and ruthenocenyl-based (Rc/Rc+) processes for both enol and keto isomers of the β-diketone FcCOCH2CORc, 4, Rc = ruthenocenyl. In CH3CN/[N(nBu)4][PF6], the ruthenocenyl moiety was oxidised to a RuIV species.

Less ion pair formation between oxidised intermediates and the electrolyte [N(nBu)4][B(C6F5)4] as compared with PF6- salts allowed electrochemical detection of up to 17 well-resolved one-electron transfer processes for the phthalocyanine [Cd2{Pc(C6H13)8}3], four for the β-diketone FcCOCH2CORc and five for [Ru2(μ-FcCOO)4·(ethanol)2][PF6]; THF as solvent enhanced peak resolution of reduced (negatively charged) species, while CH3CN complicated electrochemical interpretations due to coordination reactions.Figure optionsDownload as PowerPoint slide