Synthesis, structure, fluorescence properties and catalytic application of uranyl complexes supported by salen ligands

A series of three uranyl complexes were synthesised using salen ligands with different backbones. The synthesised ligands and complexes were duly characterised using various spectroscopic techniques which includes IR, UV–Vis and 1 H NMR. The molecular structure of the complexes C1 and C2 was determined with the aid of Single Crystal X-ray analysis, both the complexes showed distorted pentagonal bi-pyramidal geometry and the core parameters are duly evaluated. The emission property of the uranyl complexes was analysed and exhibited prominent luminescence properties with well-defined sharp peaks at 450 nm, showing an emission in blue region and their lifetimes and comparative quantum yields were calculated. TDDFT calculation was done to understand the electronic absorption and emission mechanism. The synthesised uranyl complexes and bare uranyl acetate were utilised as a catalyst for the deoxydehydration reaction of the 1,2 hexanediol. The bare uranyl acetate showed best catalytic efficiency in the conversion of 1,2 hexanediol to hexene compared to the Schiff base derived complexes. Different reaction parameters were tested with the bare uranyl acetate as a catalyst and showed the best conversion at a temperature of 140 °C, with a catalyst to substrate loading of 1:30 and a catalyst to reducing agent loading of 1:1.2.