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

Abstract

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 2–300K show that 1 and 3 show characteristic of spin-gap (Δ/kb=524.6K or 1706.6K), while 2 exhibits a strong antiferromagnetic coupling feature with J/kb=−663.2K.