Ortho-, meta-, and para-pyridyl oximinoacetoacetates and silver(I)-oximinoacetoacetate networks: Synthesis and X-ray crystallographic analyses

A series of novel oximinoacetoacetate ligands, ortho-, meta-, and para-pyridyloximinoacetoacetates, HL1, HL2 and HL3, respectively, have been synthesized and structurally characterized. Ligands HL2 and HL3 were further used for the synthesis of three new silver(I) complexes: [Ag(HL2)2]·NO3 (1) a pincer-type mononuclear complex, [Ag2(L2)2(HL2)2] (2) a centrosymmetric dimer complex, and [Ag(L3)(HL3)]n (3) a two-dimensional coordination polymer. The ligands, with multiple hydrogen donor and acceptor atoms for the formation of non-covalent hydrogen bonding interactions in the solid state, resulted in the formation of one-dimensional hydrogen bonded chains and helices. The structural studies of the AgI compounds reveal that these ligands can be efficiently used to construct hydrogen bonded two-dimensional networks. In complex 1 an extended two-dimensional network was formed through hydrogen bonds involving the OH group of the oximinoacetoacetate ligand and an O-atom of the NO3− counter anion. Complex 2 assembled into a two-dimensional multi-layered supramolecular network via O–H⋯O hydrogen bonds involving two ligand molecules. In the case of complex 3 a two-dimensional coordination polymer was formed. Unlike in complexes 1 and 2, here no classical hydrogen bonding interactions were observed in the crystal. The presence of non-classical C–H⋯O and C–H⋯N hydrogen bonds leads to the formation of three-dimensional networks in the crystal structures of all three complexes.

The availability of hydrogen bonding donor and acceptors atoms in pyridyl oximinoacetoacetates ligands make them suitable candidates for constructing supramolecular sheets and networks. Complexation of two such ligands with silver(I) salts resulted in the formation of a pincer-type mono-nuclear complex, a dimeric complex, and a two-dimensional coordination polymer. In the crystal structures of the first two complexes classical hydrogen bonding results in the formation of two-dimensional networks.Figure optionsDownload as PowerPoint slideHighlights
► Three novel o-, m- and p-pyridyloximinoacetoacetates ligands have been synthesized.
► One-dimensional hydrogen bonded chains are formed via classical hydrogen bonds.
► The ligands form silver(I) mono- and bi-nuclear complexes, and a polymeric complex.
► Non-classical hydrogen bonds lead to the formation of three-dimensional networks.