Odd–Even Effect and Unusual Behavior of Dodecyl-Substituted Analogue Observed in the Crystal Structure of Alkyltrimethylammonium–[Ni(dmit)2]− Salts

Abstract

Abstract A series of [Ni(dmit)2]− (dmit: 1,3-dithiole-2-thione-4,5-dithiolato) salts of alkyltrimethylammonium (Cn: n represents the alkyl chain length; n = 3 and 5–18) have been prepared and analyzed by X-ray structural analysis. All complex salts have been found to be composed of alternate sheets of [Ni(dmit)2]− anions and sheets of cations with a pronounced interdigitation of the alkyl chains. However, molecular arrangement differed between (C3)[Ni(dmit)2] and other (Cn)[Ni(dmit)2] (n = 5–18). Adjacent cations were aligned along the long axis of [Ni(dmit)2]− anion in C3 complex salt, while in others (C5–C18 complex salts), they were aligned toward the short axis. Such a difference in arrangement arose from correlativity between the lengths of the long axis of cation and anion, namely CLCA. Furthermore, relative orientation between the alkyl chain of cation and [Ni(dmit)2]− anion differed between the odd- and even-numbered cations for C10–C18. Whereas the plane of alkyl chain for odd-numbered cation was normal to the plane of [Ni(dmit)2]− anion, that of even-numbered cation was parallel. It was also found that C12 analog behaved like odd-numbered cations. However, in C12 salt, the end methyl group of the dodecyl group adopted unusual end-gauche conformation.