Syntheses, characterization, and crystal structures of few dioxomolybdenum(VI) complexes incorporating tridentate hydrazones

Three new cis-dioxomolybdenum(VI) complexes, [MoO 2 (L 1 )(CH 3 OH)] (1), [MoO 2 (L 2 )(CH 3 OH)] (2), and [MoO 2 (L 3 )(CH 3 OH)] (3) have been synthesized using three different tridentate hydrazone Schiff bases, (E)-N 0 -(4-oxopentan-2-ylidene)isonicotinohydrazide (H 2 L 1 ), (E)-N 0 -(4-oxo-4-phenylbutan-2- ylidene)isonicotinohydrazide) (H 2 L 2 ), and (E)-N 0 -(2,3-dihydroxybenzylidene)benzohydrazide (H 2 L 3 ), respectively. The ligands and their metal complexes were characterized by different physicochemical techniques. The molecular structures of the complexes were conclusively established by single crystal X-ray diffraction which reveals that six coordinated molybdenum(VI) atom adopts distorted octahedral geometry. The tridentate hydrazone coordinates to the metal centers in their di-anionic form. The crystal packing of the complexes also reveals that classical hydrogen bonding between adjacent units result in stair-like 1D structure for 1 while an interlocked dimer for 2 and 3, respectively. Crystal packing also reveals that further non-classical interactions lead to 2D (for 1 and 3) and 3D (for 2) supramolecular structures in their solid state. Hirshfeld surface analyses were carried out to get insight to the intermo- lecular interactions. Thermal stabilities and electrochemical behavior of the complexes have also been investigated.