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

Abstract

A complex of the general formula Mo 2(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 η 6-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-d 6 displayed typical patterns corresponding to cis-(bpy) 2M moiety. The electronic absorption spectrum of the complex revealed two bands assignable to Mo(d π) → arene(π) and Mo(d π) → 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 Mo 2(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. © 2012 Published by Elsevier Ltd. All rights reserved.