Through-space interaction mediated by a sulfoxide

Two new bisferrocenylphenylsulfoxides were synthesized and studied to determine the effect of the polar sulfoxide bond on through-space interaction between ferrocene moieties. The electronic and redox properties of these compounds were studied by ultraviolet (UV) photoelectron spectroscopy, cyclic voltammetry, differential pulse voltammetry, and density functional theory computations. Electrochemical results for 2,6-bis(ferrocenyl) thioanisole S-oxide 5b show two, fully reversible one-electron redox processes. The initial oxidation shows a 62-mV negative shift compared with the sulfide analog 2,6-bis(ferrocenyl)thioanisole, and an increased peak separation for the oxidation of 160 versus 145 mV. No peak separation is observed in 6b. No intervalence charge transfer band was observed in the complex 5b⁺¹ by UV-Visible/Near-Infrared spectroscopy, ruling out electronic communication. Thus, the through-space electrostatic interactions of the sulfoxide renders the non-equivalent ferrocenes in 5b to have different oxidation potentials.