Structural phase transition due to the flexible supramolecule of (4-cyanomethylanilinium)([18]crown-6) in [Ni(dmit)2]− crystal

Abstract

A flexible hydrogen-bonding supramolecular cation of 4-cyanomethylanilinium (CMAni⁺)-[18]crown-6 was introduced into the [Ni(dmit)₂]⁻ salt (dmit²⁻ = 2-thioxo-1,3-dithiole-4,5-dithiolate) as a counter cation to form (CMAni⁺)([18]crown-6)[Ni(dmit)₂]⁻. The rotation of the cyanomethyl group of the CMAni⁺ cation is associated with the structural phase transition at 153 K, at which temperature the space group was changed from Pbcn (high-temperature phase) to P2₁2₁2₁ (low-temperature phase). The temperature dependent dielectric constants and potential energy calculations were consistent with the rotation of the cyanomethyl group of CMAni⁺.