title: Observation of magnetic bistability in polymorphs of the [Ni(dmit)(2)](-) complexes.
abstract: Four ion-pair complexes of [Ni(dmit)(2)](-) with [NO(2)bzql](+) have been obtained, which belong to two kinds of polymorph forms, [NO(2)bzql][Ni(dmit)(2)] (1alpha and 1beta) and [NO(2)bzql][Ni(dmit)(2)].CH(3)COCH(3) (2alpha and 2beta) (where dmit = 2-thioxo-1,3-dithiole-4,5-dithiolate and [NO(2)bzql](+) = 1-(4-nitrobenzyl)quinolinium). Though 1alpha, 2alpha, and 2beta all show anionic dimerization structures at room temperature, they have different anionic and cationic arrangement fashions, which give rise to different magnetic behaviors for these polymorphs or pseudo-polymorphs. Compounds 1alpha, 1beta, and 2alpha exhibit magnetic bistabilities. In particular, 1alpha has a hysteretic loop at approximately 55 K, while 2beta does not display a spin transition in the 2-300 K range. On the basis of the crystal structure data of 2alpha in high- and low-temperature phases, the magnetic coupling feature within the [Ni(dmit)(2)](-) spin dimer was explored with the broken-symmetry approach at the UBPW91/LANL2DZ level; combined with the experimental data and theoretical analyses, the relationship between the magnetic coupling nature and the stacking pattern of [Ni(dmit)(2)](-) anions as well as the origin of the phase interconversion are discussed.
authors.affiliation: State Key Laboratory of Coordination Chemistry, Department of Chemistry, Nanjing University, Nanjing 210093, PR China.
authors.forename: Shuangquan
authors.initials: S
authors.lastname: Zang
authors.forename: Xiaoming
authors.initials: X
authors.lastname: Ren
authors.forename: Yang
authors.initials: Y
authors.lastname: Su
authors.forename: You
authors.initials: Y
authors.lastname: Song
authors.forename: Wenjun
authors.initials: W
authors.lastname: Tong
authors.forename: Zhaoping
authors.initials: Z
authors.lastname: Ni
authors.forename: Hanhua
authors.initials: H
authors.lastname: Zhao
authors.forename: Song
authors.initials: S
authors.lastname: Gao
authors.forename: Qingjin
authors.initials: Q
authors.lastname: Meng