A novel bonding of 6,7-dichloroquinoxlaine-2,3-dione, DCQX, to two molybdenum (0) metal centers: Synthesis, characterization, biological activity studies and semiempirical calculations of [(bpy)2Mo(μ2-κ2:η6-DCQX)Mo(CO)3] complex

A complex of the general formula Mo2(bpy)2(DCQX)(CO)3, (where DCQX and bpy are 6,7-dichloroquinoxaline-2,3-dione and 2,2′-bipyridine), was synthesized in two steps starting with the reaction of Mo(CO)6 with bpy then followed by the addition of DCQX ligand. Initial characterization based on the elemental and mass analyses has suggested three possible structures (1–3). In the three suggested structures the DCQX ligand bonded to two Mo(0) metal centers; to one Mo metal through its C=O functional groups and the other through the aromatic ring forming η6-arene type. In structure 1 the DCQX ligands bonded to (bpy)2Mo and Mo(CO)3 moieties, whereas in the other structures the DCQX ligands bonded to Mo(bpy)(CO) and cis-(bpy)(CO)2Mo (2) or trans-(bpy)(CO)2Mo (3) moieties. The IR studies were useful in assigning the coordination modes of the ligands especially in the carbonyl region of the spectrum. 1H NMR studies in DMSO-d6 displayed typical patterns corresponding to cis-(bpy)2M moiety. The electronic absorption spectrum of the complex revealed two bands assignable to Mo(dπ) → arene(π∗) and Mo(dπ) → bpy(π∗) MLCT transitions. The thermogravimetric analysis gave more insight into the composition and the thermal stability of the complex. The structural and vibrational behaviors of the Mo2(bpy)2(DCQX)(CO)3 complex have been elucidated using semiempirical parameterized PM3 method. Although, both DCQX ligand and the molybdenum complex showed antimicrobial activities, the complex inhibition to the studied microorganisms was higher.

A novel coordination mode of 6,7-dicloroquinoxaline-2,3-dione (DCQX) to (bpy)2Mo and Mo(CO)3 moieties. The DCQX features (κ2O,O′:η6-DCQX) bonding to the Mo metal centers.Figure optionsDownload as PowerPoint slide