The intra-annular acylamide chelate-coordinated compound: The keto-tautomer of metal (II)–milrinone complex

In the presence of N,N′-dimethyllformamide (DMF), two isostructural metal (II)–milrinone complexes formulated as M(C12H8N3O)2 (M = Co 1 and Ni 2) have been synthesized and characterized by elemental analysis, IR, TG and single crystal X-ray diffraction. The two compounds crystallize in the tetragonal system, chiral space group P43212. They exhibit similar two dimensional (2D) square grid-like framework, in which milrinone acts as a ditopic ligand with its terminal pyridine and intra-annular acylamide groups covalently bridging different metal centers. The intra-annular acylamide ligand shows a chelate-coordinated mode. Compounds 1 and 2 are stable under 200 °C. Compound 3 formulated as (C12H9N3O)4·H2O was obtained in the presence of water, the water molecule in the structure leads to the racemization of compound 3 and it crystallizes in the monoclinic system, non-chiral space group P21/c. Milrinone exhibits a keto-form in the three compounds and compounds 1–3 exhibit different photoluminescence properties.