Formation of Thermotropic and Lyotropic Liquid Crystals of Bis(N‐alkylethylenediamine)silver( I ) Nitrate

We have synthesized bis(N‐hexylethylenediamine)silver(I) nitrate ([Ag(hex‐en)2]NO3), bis(N‐octylethylenediamine)silver(I) nitrate ([Ag(oct‐en)2]NO3), and bis(N‐dodecylethylenediamine)silver(I) nitrate ([Ag(dod‐en)2]NO3) and investigated the aggregation behavior of [Ag(dod‐en)2]NO3 and [Ag(oct‐en)2]NO3 in the liquid state. An X‐ray crystallographic analysis revealed that [Ag(dod‐en)2]NO3 has a dinuclear structure in the crystalline state — the molecular composition unit is [Ag2(dod‐en)4](NO3)2, where the two dod‐en ligands bridge two silver ions that are coordinated by four nitrogen atoms. The dinuclear complex is appreciably dissociated into a mononuclear complex in solution. It was found that [Ag(oct‐en)2]NO3 and [Ag(dod‐en)2]NO3 form thermotropic liquid crystals in the temperature ranges 48−67 °C and 59−96 °C, respectively, and a lyotropic liquid crystal was also observed for [Ag(dod‐en)2]NO3 in n‐heptane at around room temperature in the presence of a small amount of water. The structures of the thermotropic and lyotropic liquid crystals of [Ag(dod‐en)2]NO3 were identified as a typical smectic A (SA) type and a nematic one, respectively. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004)