Unfolding the extraction and coordination behaviors of trivalent lanthanides by two novel cyclohexyl o-oxydiamides ligands

•Two novel cyclohexyl o-oxydiamides(R-CDA) ligands with different alkyl chain were synthesized.•Their coordination behavior with lanthanide elements has been studied.•Both 1:1 and 1:2 metal/ligand complexes can formed during extraction, in which 1:2 complexes are more stable.•The higher stability of straight chain ligand complexes may be related to the higher coordination numbers.•The coordination through the CO and COC bonds in the ligands, in which CO bond combindes more tightly.