Strong electron-accepting methylviologen dication confined in magnetic hosts: Synthesis, structural characterization, charge-transfer and magnetic properties of ((MV)₂[Ni(SCN)₅]·Cl·2H₂O)_n and ((MV)[M(N₃)₂(SCN)₂])_n (M = Mn, Co)

Three hybrid host–guest compounds ((MV)₂[Ni(SCN)₅]·Cl·2H₂O)_n (1), ((MV)[Mn(N₃)₂(SCN)₂])_n (2) and ((MV)[Co(N₃)₂(SCN)₂])_n (3) (where MV²⁺ = methylviologen dication) have been obtained by self-assembly methods and characterized by X-ray crystallography, spectral methods and magnetic measurements. Compound 1 shows a quasi-two-dimensional structure which is formed by novel single thiocyanate-bridged Ni(ii) chains connected through S⋯S interactions. Compounds 2 and 3 are isostructural, containing single µ_1,3-azide bridged Mn(ii)/Co(ii) square layers. MV²⁺, as a strong electron-acceptor and a template, is embedded between the anionic layers in all three compounds. The charge-transfer (CT) interactions between MV²⁺ and the anionic hosts have been revealed by structural analysis and UV-vis diffuse reflection spectroscopy. The magnetic studies of the compounds show antiferromagnetic interactions between adjacent metal ions (J = –34.52(7) cm^–1 for 1, J = –3.90(2) cm^–1 for 2 and J = –10.96(6) cm^–1 for 3).