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

• Published in: Inorganica Chimica Acta 2016-09, Vol.451, p.92-101
• Main Authors: Biswal, Debanjana, Pramanik, Nikhil Ranjan, Chakrabarti, Syamal, Drew, Michael G.B.
• Format: Article
• Language: English
• Subjects: 4,4′-Azopyridine; Crystal structure; DFT calculations; Dioxomolybdenum(VI); Schiff base ligand; Supramolecular interactions
• ISSN: 0020-1693; 1873-3255
• DOI: 10.1016/j.ica.2016.07.004

By controlling the steric demands of the Schiff base, supramolecular architectures of Mo(VI) complexes containing diverse cavity sizes are formed. [Display omitted] •New pillared binuclear dioxo-Mo(VI) complexes with ONS donor ligand and 4,4′-azpy.•Spectral, electrochemical, thermal and structural characterizations of complexes.•Rectangular cavities are formed via hydrogen bonding and π-π stacking interactions.•The DFT calculations provide an energetic study of the non-covalent interactions. 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.