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

Abstract

Enhanced electrochemical resolution of anodic processes is possible in the presence of [N( n Bu) 4][B(C 6F 5) 4], 1, as supporting electrolyte over that obtained in the presence of [N( n Bu) 4][PF 6]. By changing the anion of the supporting electrolyte to a salt having [B(C 6F 5) 4] −, anions, electrochemical processes of especially cationic analytes can benefit. Thus, the redox chemistry of 0.5 mmol dm −3 solutions of [Ru 2(μ-FcCOO) 4·(CH 3CH 2OH) 2][PF 6], 2, Fc = ferrocenyl, in CH 2Cl 2/[N( n Bu) 4][B(C 6F 5) 4] were found to involve four well-resolved ferrocenyl-based electrochemical reversible redox processes as well as reduction of Ru III–Ru II. At 1.0 mmol dm −3 concentrations of 2, or in the presence of [N( n Bu) 4][PF 6], the four ferrocenyl processes coalesced into only two waves as a result of (Fc +)⋯( PF 6 - ) ion paring. Seventeen of the possible 18 one-electron transfer processes of the biscadmium trisphthalocyaninato complex [Cd 2{Pc(C 6H 13) 8} 3], 3, could be observed in THF/[N( n Bu) 4][B(C 6F 5) 4], but the electrochemical window of CH 2Cl 2/[N( n Bu) 4][B(C 6F 5) 4] only allowed detection of 15 of these processes. Although reduction processes were unaffected, THF solvation leading to species such as ( 3 n +)(THF) x with 1 ⩽ n ⩽ 4 and x ⩾ 1 as well as ion pair formation of the type ( 3 n +)⋯( PF 6 - ) prevented good resolution of oxidation processes. The CH 2Cl 2/[N( n Bu) 4][B(C 6F 5) 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 FcCOCH 2CORc, 4, Rc = ruthenocenyl. In CH 3CN/[N( n Bu) 4][PF 6], the ruthenocenyl moiety was oxidised to a Ru IV species.