Unprecedented stacking of MV2+ dications and MV˙+ radical cations in the mixed-valence viologen salt (MV)2(BF4)3 (MV = methylviologen)

Abstract

Using a slow liquid–gas diffusion method, the mixed-valence viologen salt (MV)₂(BF₄)₃ (1) and the radical cation salt (MV)(BF₄) (2) are crystallized. Both structures contain regular stacks of MV˙⁺ radical cations (2) or alternating MV˙⁺ and MV²⁺ entities (1). A short intrastack intermolecular separation (3.23 Å) unprecedently reveals strong interactions between MV²⁺ and MV˙⁺ in 1.