Syntheses, crystal structures, and magnetic properties of three new molecular solids based on bis(maleonitriledithiolate)Ni(III) monoanion and substituted chlorobenzyl-4-dimethylaminopyridinium

• Crystal structures of three molecular metals were obtained.
• The Ni(III) ions of 1 form a non-uniform 1D magnetic chain.
• The Ni(III) ions of 2 form a 1D uniform chain.
• The [Ni(mnt)2]− anions of 3 show a stepwise structure.
• Three molecular metals exhibit an interesting characteristic of spin-gap.

Three new molecular solids, [nClBzPyN(CH3)2][Ni(mnt)2]([BzPyN(CH3)2]+ = benzyl-4-dimethylaminopyridinium; mnt2− = maleonitriledithiolate; n = 2(1), 3(2), 4(3)), have been prepared and characterized. The [Ni(mnt)2]− anions of 1 and 2 form a 1D column in which the former is non-uniform one with the Ni⋯Ni distances of 4.412 and 6.072 Å, and the latter is uniform one with the distance of 7.352 Å, while the ones of 3 show a stepwise structure through Ni⋯S, Ni⋯C, π⋯π, or C⋯N short interactions. The [2ClBzPyN(CH3)2]+ cations(C) and [Ni(mnt)2]− anions (A) of 1 stack into a 1D column with a ⋯ACCACCA⋯ sequence, while the cations stake into a 1D column via N⋯π and Cl⋯Cl short interactions for 2. The change of the chlorine position on the benzyl ring from ortho, meta to para-position results in the significant differences in stacking modes of these molecular solids. Magnetic susceptibility measurements in the temperature range 2–300 K show that 1, 2 and 3 exhibit a spin gap transition around 172, 150 and 92 K.

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