Insight into selective separation of Am(III)/Eu(III) with novel ligands using (1,10-phenanthroline-2,9-diyl)bis(indolin-1-ylmethanones) as a new skeleton: A scalar relativistic DFT study

•Using IDL-DAPhen as a novel skeleton to design ligands, and study on Am(III)/Eu(III) separation with the ligands was carried out.•It was found that the coordination ability of carbonyl oxygen is stronger than that of pyridine nitrogen.in the IDL-DAPhen ligands.•Discovering that IDL-DAPhen ligands modified with substituent groups lead to different coordination abilities and separation selectivity for Am (III)/Eu (III).•Reasonable use of a variety of novel qualitative and quantitative theoretical analysis methods (e.g.,IRI, IGMH and ETS-NOCV).