The Amide Group as Modulator of Crystalline and Liquid Crystalline Structures in Isocyano-Alkylanilide Silver(I) Complexes

Silver­(I) complexes [AgX­(CNR] and [Ag­(CNR)₂]­X (X = anionic ligand), containing an amide-functionalized isocyanide, CNR = CN–C₆H₄–NHCOR, have been synthesized and their X-ray structures have been determined for [Ag­(X)­(CN–C₆H₄–NHCOCH₃)] (X = NO₃^–, CF₃SO₃^–) and [Ag­(CN–C₆H₄–NHCOCH₃)₂]­X (X = NO₃^–, CF₃SO₃^–, BF₄^–). All the crystal structures show a packing of polymeric chains formed through Ag–OC_amide interactions. These chains associate in layers through hydrogen bonds involving the amide group, and by further interactions of the metal ion with oxygen-donor moieties. Substitution of the Me group in the amide by a nonyl chain (R = C₉H₁₉) leads to neutral [Ag­(NO₃)­(CN–C₆H₄–NHCOC₉H₁₉)] and ionic [Ag­(CN–C₆H₄–NHCOC₉H₁₉)₂]­X (X = NO₃^–, CF₃SO₃^–, H₂₅C₁₂OSO₃^–, BF₄^–) mesomorphic complexes. All of them display smectic liquid crystalline phases compatible with the crystal structures found for the methyl derivatives, and FTIR/ATR spectroscopy confirms that the intermolecular interactions observed in the solid state are preserved in the mesophase.