Supramolecular cation assemblies of hydrogen-bonded (NH4+/NH2NH3+)(crown ether) in [Ni(dmit)2]-based molecular conductors and magnets

Hydrogen-bonded supramolecular cation assemblies of (NH4+/NH2-NH3+)(crown ether), where the crown ether is [12]crown-4, [15]crown-5, or [18]crown-6, were incorporated into electrically conducting [Ni(dmit)(2)] salts (dmit(2-) = 2-thioxo-1,3-dithiole-4,5-dithiolate). (NH4+)([12]crown-4)[Ni(dmit)(2)](3)(CH3CN)(2) had a pyramidal shape, while ionic channels were observed in (NH4+)0.88([15]crown-5)[Ni(dmit)(2)](2) and (NH4+)(0.70)- ([18]crown-6)[Ni(dmit)(2)](2). Both (NH4+)(0.88)([15]crown-5) and (NH4+)(0.70)([18]crown-6) contained regularly spaced [Ni(dMit)(2)] stacks formed by N-(HO)-O-... hydrogen bonding between the oxygen atoms in crown ethers and the NH4+ ion. NH4+ occurred nonstoichiometrically; there were vacant ionic sites in the ionic channels. The ionic radius of NH4+ is larger than the cavity radius of [15]crown-5 and [18]crown-6. Therefore, NH4+ ions could not pass through the cavity and were distributed randomly in the ionic channels. The static disorder caused the conduction electrons to be randomly localized to the [Ni(dMit)(2)] stacks. Hydrazinium (NH2NH3+) formed the supramolecular cations in (NH2-NH3+)([12]crown-4)(2)[Ni(dmit)(2)](4) and (NH2-NH3+)(2)([15]crown-5)(3)[Ni(dmit)(2)](6), possessing a sandwich and club-sandwich structure, respectively. To the best of our knowledge, these represent the first hydrazinium-crown ether assemblies to be identified in the solid. In the supramolecular cations, hydrogen bonding was detected between the ammonium or the amino protons of NH2-NH3+ and the oxygen atoms of crown ethers. The sandwich-type cations coexisted with the [Ni(dmit)(2)] dimer stacks. Although the assemblies were typically semiconducting, ferromagnetic interaction (Weiss temperature = +1 K) was detected in the case of (NH2-NH3+)(2)([15]crown-5)(3)[Ni(dmit)(2)](6). The (NH2- NH3+)(0.8)([18]crown-6)[Ni(dmit)(2)](2) and (NH4+)(0.76)([18]crown-6)[Ni(dmit)(2)](2) crystals were isomorphous. The large and flexible [18]crown-6 allowed for maintaining the same ionic channel structure through replacement of the NH4+ cation by NH2-NH3+.