Uranyl(VI) Mixed-ligand complex synthesis and characterization using 4-acylhydrazone-5-pyrazolone and 4-acylpyrazolone: Covalency, crystal assay, DFT study and Hirshfeld analysis

•HLA acylpyrazolone as bidentate ligand, its Schiff base Bz-HLA as tridentate ligand and Uranyl mixed ligand complex using these two ligands were synthesized and characterized using FTIR, 1HNMR, 13CNMR, TG-DTA, UV/Vis, CV, and Single-crystal XRD techniques.•Pentagonal bipyramidal geometry, vibrations of stretching, redox behaviour and non-electrolytic behaviour were scrutinized.•Crystal strength explanation by interaction energies and energy frameworks generated through Hirshfeld surface analysis of Bz-HLA ligand's crystal structure.•Calculations of Sinha's covalency parameters from UV–vis spectra and theoretical study of ligand and complex by DFT and calculation of Global index parameters.