Insight into weakly antiferromagnetic coupling behavior in a non-integer oxidation state bis(2-thioxo-1,3-dithiole-4,5-dithiolate)nickelate molecular semiconductor

Abstract

In (ImH)[Ni(dmit) 2 ] 2 , the [Ni(dmit) 2 ] 0.5− anions form dimeric stack, and the weakly AFM couplings between anion dimers are achieved through magnetic dipole–dipole interactions. • A non-integer oxidation state [Ni(dmit) 2 ] 0.5− salt was prepared by chemical oxidation together with solvent evaporation. • The columnar [Ni(dmit) 2 ] 2 − stacks are connected by intermolecular S…S interactions into a monolayer. • There exist quietly weak AFM couplings between [Ni(dmit) 2 ] 2 − dimers owing to magnetic exchange through dipole–dipole interactions. In this study, we prepared a salt, (ImH)[Ni(dmit) 2 ] 2 ( 1 ; ImH + = imidazolium; dmit 2− = 2-thioxo-1, 3-dithiole-4, 5-dithiolate), by a facile approach of chemical oxidation together with solvent evaporation at ambient condition. (1) was characterized by microanalysis for C, H and N elements, IR spectroscopy, TG and DSC techniques. 1 crystallizes in triclinic space group P − 1, with two different [Ni(dmit) 2 ] species (Ni1 and Ni2) and one ImH + cation in an asymmetric unit. The characteristic C C, C S and Ni S bond lengths in [Ni(dmit) 2 ] species demonstrated that the valences of two different [Ni(dmit) 2 ] species are −0.5. The anions form dimeric stacks in 1 , which are further connected into monolayers by inter-stack S…S interactions. 1 shows semiconducting feature with σ DC = 1.45 × 10 −3 S cm −1 at 293 K and E a = 0.17 eV; and smaller Weiss constant (−0.67 K) owing to the magnetic couplings being achieved through weak dipole–dipole interactions.