New pillared dioxomolybdenum(VI) complexes with ONS donor ligands and 4,4′-azopyridine spacer: 3D metal-organic supramolecular architectures and DFT calculations

Abstract

Two new pillared binuclear dioxomolybdenum(VI) complexes [(MoO2L1)2(4,4′-azpy)] (1) and [(MoO2L2)2(4,4′-azpy)] (2) have been synthesized by the reaction of MoO2(acac)2 with Schiff base ligands (H2L1 and H2L2) derived from 2-hydroxyacetophenone and S-benzyl/S-methyl dithiocarbazates respectively and 4,4′-azopyridine as a spacer. Crystal and molecular structures of the investigated binuclear complexes 1 and 2 were determined by single crystal X-ray diffraction. The two complexes have similar centrosymmetric dimeric structures in which each molybdenum atom occupies distorted octahedral six-coordinate environments being bonded to a dianionic tridentate ONS donor ligand via phenolate oxygen, imine nitrogen and thioenolate structure as well as two terminal oxygen atoms and a nitrogen atom of the bridging 4,4′-azpy ligand. Complexes 1 and 2 give rise to 3D metal-organic supramolecular frameworks having rectangular cavities formed via hydrogen bonding and π-π stacking interactions. The complexes were further characterized by elemental analysis, spectroscopic methods (IR, 1H NMR and UV–vis), electrochemical study and thermogravimetric analysis. DFT calculations were used to study the electronic properties of the complexes.