Liquid crystals of silver complexes derived from simple 1-alkylimidazoles

Abstract

A homologous series of silver complexes of 1-alkylimidazoles (R-im, R = C_nH_2n+1, where n = 10, 12, 14, 16 and 18) was synthesized. All the C_nH_2n+1-im ligands are non-mesomorphic. Upon complexation, all the [Ag(C_nH_2n+1-im)₂][NO₃], except for n = 10, exhibit liquid crystalline properties. The crystal structure of [Ag(C₁₂H₂₅-im)₂][NO₃] shows that the silver center is two-coordinate and adopts a U-shaped conformation with bilayer packing. The non-mesomorphic [Ag(C₁₆H₃₃-bim)₂][NO₃] (bim = benzimidazole) has a three-coordinate silver ion and has a chair conformation with monolayer stacking. Non-mesomorphic [Ag(C₁₆H₃₃-bim)₂][BF₄] has a linear geometry around the silver ion and also has a chair conformation. The mesophase for the Ag–(C_nH_2n+1-im) complexes has been identified as the smectic A (SmA) phase. [Ag(C₁₆H₃₃-im)₂]⁺ with four different anions, NO₃⁻, BF₄⁻, PF₆⁻ and CF₃SO₃⁻ were compared. Of the four Ag–im complexes, only that with the CF₃SO₃⁻ anion does not show liquid-crystal behavior.