•Two molecular solids containing Ni(mnt)2− monoanion were prepared and characterized.•The Ni(mnt)2− anions in 1 form a non-uniform 1D chain with the Ni⋯Ni distances of 3.443, 3.935 and 3.968Å.•The Ni(mnt)2− anions in 2 form a uniform 1D magnetic chain with a Ni⋯Ni distance of 4.148Å.•Compound 1 exhibits a characteristic of spin-gap around 86K upon the temperature is lowed. Two molecular metals, 2F4BrBzTPPNi(mnt)2·H2O (1) and 2Br4FBzTPPNi(mnt)2 (2) (2F4BrBzTPP+=1-(2′-fluoro-4′-bromobenzyltriphenylphosphonium, 2Br4FBzTPP+=1-(2′-bromo-4′-fluorobenzyltriphenylphosphonium, mnt2−=maleonitriledithiolate), have been synthesized and structurally characterized by single crystal X-ray diffraction. Compound 1 crystallizes in the triclinic space group P−1, while 2 does in the monoclinic space group P21/c. The Ni(III) ions from Ni(mnt)2− anion of 1 form a 1D non-uniform chain through Ni⋯S, Ni⋯Ni and π⋯π interactions with the Ni⋯Ni distances of 3.443, 3.935 and 3.968Å, as well as CH⋯F, CH⋯N, CH⋯π, and π⋯π weak interactions exist in 1. The anions and cations in 2 stack into segregated structure, and the anions give rise to a 1D uniform column with a Ni⋯Ni distance of 4.148Å. Magnetic measurements have shown that 1 exhibits a characteristic of spin-gap (Δ/kb=267.5K) around 86K, while 2 shows an antiferromagnetic coupling feature with J=−15.4cm−1 upon the temperature is lowed.