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The four new multivalent ligands 5-8 derived from calix[4]arene and thiacalix[4]arene backbones in 1,3-Alternate conformation bearing ortho-imino- and ortho-amino-methylpyridine chelating sites have been designed, prepared and characterized. Owing to the imposed 1,3-Alternate conformation of the backbone, ligands 5-8 offer two coordinating pockets composed of two sets of chelates located above and below the mean place of the macrocyclic framework. Ligands 6-8, independent of the nature of the anion associated with Ag+ cation, form binuclear silver complexes (AgX, X = BF4-, PF6-, SbF6-, AsF6-, NO3-) in solution and in the solid state. Ligand 7, in the presence of an excess of Ag+, also forms tetranuclear silver complexes 7-(AgBF4)4, and 7-(AgNO3)4 in presence of two different auxiliary ligands (H2O or NO3-) that have been characterized in the solid state. Due to a rather short Ag-Ag distance of ca 2.89 A, the tetranuclear complex 7-(AgBF4)4 is emissive in the solid state, at 298 K (λexc = 295 nm, λem = 425 nm) resulting from argentophilic interactions between the closely positioned silver cations.

The synthesis of methylated calix[4](aza)crowns and their complexing properties towards Co2+, Ni2+ and Cu2+ are described. The crystal structure of one of those ligands, hydrogen bonded to a picric acid molecule via a water molecule, is given.