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.