Ionic channel structures in [(M+)(x)([18]crown-6)][Ni(dmit)(2)](2) molecular conductors

The [(M+),([18]crown-6)] supramolecular cations (SC), in which M+ and [18]c rown-6 are alkali metal ions (M+ = Li+, Na+, and Cs+), and 1,4,7,10,13, 16- hexaoxacyclooctadecane, respectively, form ionic channel structures through the regular stacks of [18]crown-6 in [Ni(dmit)(2)]-based molecular conduct ors (dmit(2) =2-thioxo-1,3-dithiole-4,5-dithiolate). In addition to the [Ni (dmit)(2)] salts that have the ionic channel structures (these salts are ab breviated as type I salts), Li+ and Na+ form dimerized [(M+)(2)([18]crown-6 )(2)] units in the crystals (type II salts). The K+ and Rb+ are coordinated tightly into the [18]crown-6 cavity to form typical diskshape SC+ units in the corresponding [Ni(dmit)(2)] salts (type III salts). The type I, II, an d III salts have typical stoichiometries of [(M+),([18]crown-6)]-[Ni(dmit)( 2)](2), [(M+)([18]crown-6)(H2O)(x),(CH3CN)(1.5-x)][Ni(dmit)(2)](3) (x = 1 f or Li+ or 0.5 for Na+). and [M+([18]crown-6)][Ni(dmit)(2)](3), respectively ; the salts of the same type are isostructural. In agreement with the trime r structures of [Ni(dmit)(2)] in the type II and III salts, they exhibit se miconducting behavior with electrical conductivities at 300 K (sigma (300K) of 0.01 - 0.1 S cm(-1). Type I salts contain a regular stack of partially oxidized [Ni(dmit)(2)] units, which form a quasi one-dimensional metallic b and within the tight-binding approximation regime. The electrical conductiv ities at 300 K are 10 - 30 S cm(-1), and an almost temperature-independent conductivity was observed at higher temperatures, However, the one-dimensio nal electronic structures in these salts are strongly influenced by the sta tic and dynamic structures of the coexisting ionic channel. The Na+ salt is a semiconductor, whose magnetic behavior is described by the disordered on e-dimensional antiferromagnetic chain. On the other hand, the Cs+ salt is a exhibits metallic properties with 2k(P) instability at room temperature. T he Li+ salt shows a gradual transition from the high-temperature metallic p hase to the low-temperature one-dimensional antiferromagnetic semiconductor phase, which was associated with the freezing of Li+ motion at lower tempe ratures. The preferential crystallization of type I salts was possible by c ontrolling the equilibrium constant (K-c) of the complex formation between M+ ions and the [18]crown-6 molecule. The ionic channel structures were obt ained when the K-c was low in the electrocrystallization solution, while ty pe II or III salts were formed in the high K-c region.