Octabutylthiophthalocyaninatoiron(ii): electrochemical properties and interaction with cyanide

Abstract

The preparation of the thiol-derivatised iron(II) phthalocyanine (FePc) complex, 2,3,9,10,16,17,23,24-octabutylthiophthalocyaninatoiron(II), FePc(SC₄H₉)₈, is described. Electrochemical data obtained by both cyclic voltammetry and Osteryoung square wave voltammetry in DMF showed four redox couples. Kinetics and equilibrium measurements for the interaction of cyanide with FePc(SC₄H₉)₈ at 25.0 ± 0.5 °C in both DMSO and DMF are reported. Gradual spectroscopic changes were only observed for the formation of the dicyano complex, [(CN)₂FePc(SC₄H₉)₈]²⁻. This complex is formed with equilibrium constants, K, of (6.8 ± 0.8) × 10² dm³ mol⁻¹ in DMF and (1.3 ± 0.2) × 10³ dm³ mol⁻¹ in DMSO. Pseudo-first-order rate constants, k_4r, were also estimated to be (1.9 ± 0.1) × 10⁻² and (8.2 ± 0.3) × 10⁻² dm³ mol⁻¹ s⁻¹ in DMF and DMSO, respectively. These results agree with the weak electron-donating properties of the peripheral butylthio-substituents on the phthalocyanine ring and the O-bonded trans DMF.