The synthesis, crystal structures, magnetic properties, and single molecular conductances of two linear trinickel string complexes, [Ni3(mpta)4(NCS)2] (2) and [Ni3(mpta)4(CN)2] (3), supported by sulfur-containing Hmpta (1) ligands are presented (Hmpta = 4-methylpyridylthiazolylamine). Compounds 2 and 3 possess a 1D trinickel backbone coordinated by four mpta– ligands. Within the trinickel framework, the two terminal high-spin (S = 1) Ni ions are strongly antiferromagnetically coupled (J = –91 cm–1 in 2 and –79 cm–1 in 3). As the axial CN– ligand is very basic and strongly pulls the terminal Ni ions away from the central Ni ion, the Ni–Ni distances in 3 (ca. 2.52 Å) are longer than those in 2 (ca. 2.47 Å). The lengthening of the Ni–Ni bond lengths causes 3 to exhibit weaker antiferromagnetic interactions and lower single molecular conductance [R = 7.1 (±1.5) MΩ for 2 and R = 11.1 (±3.9) MΩ for 3].