Supramolecular aggregation in alkaline earth metal 3- and 4-hydroxybenzoates using 1,10-phenanthroline auxiliary

763-774The interaction of group 2 metals with 3- and 4-hydroxybenzoic acids in presence of chelating N-donor ligand 1,10-phenanthroline (phen) has been investigated. The 3-hydroxybenzoate derivatives [Ca(3-hba)2(phen)2(H2O)3]n (1), [Sr(3-hba)2(phen)2(H2O)2]n (2), and [Ba(3-hba)2(phen)2(H2O)2]n (3) have been obtained by treatment of the corresponding metal carbonates with 3-hydroxybenzoic acid and 1,10-phenanthroline, while the 4-hydroxybenzoate derivatives [Ca(4-hba)2(phen)2(H2O)] (4), [Sr(4-hba)2(phen)2(H2O)4] (5), [Ba(4-hba)2(phen)2(H2O)2] (6) have been prepared by a similar method using 4-hydroxybenzoic acid. The compounds have been characterized by elemental analysis, thermal analysis, and infrared and 1H NMR spectroscopic studies. The solid-state structures of (2-4) and (6) have been established by single-crystal X-ray diffraction studies. The compounds are monomeric in the solid state although they exhibit considerable variations in their molecular structures in terms of binding mode of the hba ligands and the coordination geometry around the metal ions. All the compounds form polymeric networks in the solid state with the aid of O-HO, C-HO and N-HO hydrogen bonding and p-p interactions