Supramolecular aggregation in alkaline earth metal amino Benzoates with 1,10-phenanthroline auxiliary

Reactions of 2-, 3- and 4-aminobenzoic acids with alkaline earth metals in the presence of 1,10-phenanthroline (phen) have been investigated. Compounds [Ca(2-aba)(2)(phen)(2)(OH2)(2)] (1), [Ca(3-aba)(2)(phen)(OH2)(3)](phen)(H2O) (2) and [Ca(4-aba)(phen) (OH2)41(4-aba)(phen) (3) were synthesized from the corresponding metal precursors and 1,10-phenanthroline. The synthesis of [Sr(2-aba)(2)(phen)(2)(OH2)(2)] (4), [Sr(3-aba)(2)(phen)(2)(OH2)] (5), [Sr (4-aba)(phen)(OH2)(4)](4-aba)(phen) (6), [Ba(2-aba)(2)(phen)(2)(OH2)2], (7), [Ba(3-aba)2(phen)2(OH2)41 (8), and [Ba(4-aba)(phen)2(OH2)31 (4-aba)(H2O) (9) were accomplished from corresponding metal carbonates and aminobenzoic acids. The single crystal X-ray diffraction studies show that the complexes exist as discrete monomeric units held together by hydrogen bonding. The 2-aminobenzoate complexes 1, 4, and 7 are found to be isostructural where the metal ions are eight coordinated. The 4-aminobenzoate complexes 3, 6, and 9 exist as ion pairs. Carboxylate ligand prefers to bind the metal in a monodentate mode in most of these complexes. The molecules interact in the solid state via nonbonding interactions like hydrogen bonds and pi-pi stacking.