Syntheses, crystal structures and magnetic properties of three new molecular magnets by self-assembly of bis(maleonitriledithiolate)nickel(III) anion and substituted N,N′-dibenzylpiperidinium

•Three molecular magnets containing [Ni(mnt)2]− anion were successfully obtained.•The anions and the cations in 1 and 3 stack into segregated columns.•The Ni(III) ions of 1 and 3 form a alternating 1D zigzag magnetic chain.•The [Ni(mnt)2]− anions of 2 form a dimer.•Compounds 1 and 3 show interesting characteristic of spin-gap.

Three new molecular magnets [DiFBzPid][Ni(mnt)2]·0.5CH3COCH3(1), [DiBrBzPid][Ni(mnt)2](2) and [DiNO2BzPid][Ni(mnt)2](3) have been obtained by self-assembly of the [Ni(mnt)2]− (mnt2− = maleonitriledithiolate) anion and [DiRBzPid]+ ([DiRBzPid]+ = N,N′-diRbenzylpiperidinium; R = F, Br, NO2) cation. The Ni(III) ions of the anions in 1 and 3 form a 1D alternating magnetic chain within a [Ni(mnt)2]− column through Ni⋯S, S⋯S, S⋯N, S⋯C or C⋯N short interactions, while the anions in 2 form a dimer. The cations in three compounds stack into a 1D column in different shapes via p⋯π, F⋯F, Br⋯Br, and O⋯O weak interactions or CH⋯π hydrogen bonds. In addition, the [DiNO2BzPid]+ cations (C) and [Ni(mnt)2]− anions (A) of 3 stack into a 1D alternative column with a A–CC–A–CC–A sequence. The change of the substituent group in the benzyl ring from F(1) to Br(2) and NO2(3) results in the significant differences in the anion–anion, anion–cation and cation–cation stacking modes of 1, 2 and 3. Magnetic susceptibility measurements in the temperature range of 2–300 K show that 1 and 3 show characteristic of spin-gap (Δ/kb = 524.6 K or 1706.6 K), while 2 exhibits a strong antiferromagnetic coupling feature with J/kb = −663.2 K.

Graphical abstractThree new molecular magnets [DiFBzPid][Ni(mnt)2]·0.5CH3COCH3(1), [DiBrBzPid][Ni(mnt)2](2) and [DiNO2BzPid][Ni(mnt)2](3)(mnt2− = maleonitriledithiolate) anion and [DiRBzPid]+ ([DiRBzPid]+ = N,N′-diRbenzylpiperidinium; R = F, Br, NO2) have been investigated. The differences in the stacking mode of the anions and the cations result in the differences in magnetic coupling properties, both 1 and 3 show characteristic of spin-gap, while 2 exhibits an antiferromagnetic coupling feature.Figure optionsDownload full-size imageDownload as PowerPoint slide