Synthesis, characterization, and biological relevance of hydroxypyrone and hydroxypyridinone complexes of molybdenum

We have prepared a number of complexes of the type cis-MoO₂L₂ where L represents a hydroxypyronato or hydroxypyridinonato ligand. Both the maltol (3-hydroxy-2-methyl-4-pyrone, Hma) and kojic acid (5-hydroxy-2-hydroxymethyl-4-pyrone, Hka) complexes, cis-MoO₂(ma)₂ (1) and cis-MoO₂(ka)₂ (2), have been characterized by X-ray diffraction studies. The pyrone ligands are bound to molybdenum in a cis bidentate fashion via the deprotonated hydroxyl groups and the ketone moieties. Crystals of 1 are orthorhombic, a = 12.107 (1), b = 8.6169 (8), c = 16.472 (1) A, Z = 4, space group Pca2₁, and those of 2 are monoclinic, a = 8.4591 (5), b = 16.3453 (10), c = 10.2954 (7) A, β = 103.0320 (10)°, Z = 4, space group P2₁/c. Hydroxypyridinone molybdenum complexes have been prepared for both maltol and kojic acid derivatives with the substituents Me, n-Pr, CH₂Ph, Ph at the ring nitrogen. Crystals of the 3-hydroxy-2-methyl-1-phenyl-4-pyridinone (Hppp) derivative, MoO₂(ppp)₂ (9), are monoclinic, a = 10.9476 (6), b = 13.5353 (9), c = 17.4877 (10) A, β = 93.465 (4)°, Z = 4, space group P2₁/n. Initial investigations into the effects molybdenum compounds have on diabetic hearts are presented. Both Na₂MoO₄ (used as a control) and 1 were effective in lowering blood glucose and free fatty acid levels. Diabetic rats treated with molybdate showed significant improvements in postischemic cardiac function.