Structural diversity in binuclear complexes of alkaline earth metal ions with 4,6-diacetylresorcinol

A new series of binuclear and mixed-ligand complexes with the general formula: [ M 2 ( H n L ) m L x ′ ( H 2 O ) y Cl z ] ; where M = Mg(II), Ca(II), Sr(II) and Ba(II); H2L = 4,6-diacetylresorcinol, the secondary ligand L′ = acetylacetone (acac), 8-hydroxyquinoline (8-HQ) or 2,2′-bipyridyl (Bipy), n = 0–2, m = 1, 2, x = 0, 1, 2, 4, y = 0, 2, 4, 5 and z = 0–2; have been synthesized. They have been characterized by the analytical and spectral methods (IR, 1H NMR and mass) as well as TGA and molar conductivity measurements. The spectroscopic and conductance data suggested that the H2L ligand behaves as a neutral, monobasic or dibasic tetradentate ligand, depending on the basicity of the secondary ligand, through the two phenolic and two carbonyl groups. Binuclear octahedral geometry has been assigned to all of the prepared complexes in various molar ratios 2:2; 2:2:2; 1:2:1 and 1:2:4 (L:M:L′). Molecular orbital calculations were performed for the ligands and their complexes using Hyperchem 7.52 program on the bases of PM3 level and the results were correlated with the experimental data. The ligand and some of its alkaline metal(II) complexes showed antibacterial activity towards some of Gram-positive and Gram-negative bacteria, yeast (Candida albicans) and fungus (Aspergillus fumigatus).