Paramagnetic and semiconducting 1:1 salts of 1,1'-disubstituted ferrocenes and [Ni(mnt)(2)](-). Synthesis, structure, and physical properties

The ferrocene-based electron donors 1,1'-bis[2-(4-(methylthio)phenyl)-(E)-ethenyl]ferrocene (2), 1,1'-bis[2-(4-methoxyphenyl)-(E)-ethenyl]ferrocene (3), 1,1'-bis[(1,3-dithiolo[4,5-b][1,3]dithiol-2-ylidene)methyl]ferrocene (4), and 1,1'-bis[(1,3-benzodithiol-2-ylidene)methyl]ferrocene (5) were found to react with ferrocenium bis(maleonitriledithiolato)nickelate (1-) ([FeCp(2)](+)[Ni(mnt)(2)](-), 6) to afford the corresponding 1:1 paramagnetic salts 7-10, containing 1,1'-disubstituted ferrocenium derivatives. SQUID magnetic susceptibility measurements of these new compounds showed a behavior dominated by antiferromagnetic interactions within pairs of [Ni(mnt)(2)](-) ions. Pressed pellets of compounds 7 ([2][Ni(mnt)(2)]) and 9 ([4][Ni(mnt)(2)]) are semiconducting, with a relatively large conductivity activation energy (0.85 and 1.13 eV). Crystals of 7 reveal the monodimensional nature of the compound. Each separate stack of [Ni(mnt)(2)](-) ions is flanked by two ferrocenium stacks. Ni-Ni distances alternate between 3.67 and 3.99 Angstrom.