Two Polymorphs of (Anilinium)(18-Crown-6)[Ni(dmit)2]: Structure and Magnetic Properties

Two polymorphs of monovalent [Ni(dmit)2]- (dmit2-=2-thioxo-1,3-dithiole-4,5-dithiolate) crystals A and B, (anilinium)(18-crown-6)[Ni(dmit)2], were prepared, and the structure and magnetic properties were investigated. In these crystals, the [Ni(dmit)2]- molecules form dimers, which arranged into chains between the supramolecular cation structure (anilinium) (18-crown-6). In crystal A, supramolecular cation formed a regular stack, inducing ladder structure of [Ni(dmit)2], whose magnetism had been well fitted by spin ladder equation with the spin gap of DELTA=190 K. Crystal B is ca. 3% more densely packed compared to crystal A. Due to the dense packing, supramolecular cation stack is distorted, which prevented the intermolecular interaction between [Ni(dmit)2]- dimers in direction corresponds to the ladderleg direction in crystal A. Reflecting the [Ni(dmit)2]- arrangement, crystal B showed a temperature dependence of magnetic susceptibility well reproduced by the singlet-;triplet thermal activation model, whose antiferromagnetic exchange interaction (2J) was 140 K.