Complexation Behavior and Selective Separation of Am ³⁺ /Eu ³⁺ With Four Novel Ligands Based on Skeleton HDBM: A Scalar Relativistic DFT Study

ABSTRACT An 3+ /Ln 3+ separation is fundamental to mitigating the environmental impact of spent nuclear fuel. A thorough investigation into the separation mechanisms of An 3+ /Ln 3+ and coordination interactions with promising extractants is essential for reducing the environmental hazards posed by nuclear waste. In this study, employing scalar relativistic density functional theory (DFT), we designed ligands L H , L Et , L Br , and L Ca based on a novel skeleton, (5 H ‐cyclopenta[2,1‐ b :3,4‐ b ′]dipyridine‐2,8‐diyl)bis((1 H ‐pyrazol‐1‐yl)methanone) (HDBM), which was modified with different substituent groups (G = ‐H, ‐CH 2 CH 3 , ‐Br, and ‐COOH) to systematically assess their complexation behaviors and selective separation of Am 3+ /Eu 3+ . Bonding characterization confirms that the four classes of ligands with N, O donor atoms exhibit a stronger selective coordination tendency toward Am 3+ than Eu 3+ with a stronger tendency for selective coordination. For further corroboration, we also performed molecular orbitals (MOs), Independent gradient model based on Hirshfeld (IGMH), frontier molecular orbitals (FMOs), and extended transition state‐natural orbitals for chemical valence (ETS‐NOCV), and other analyses, which consistently demonstrate that the ligands interact more strongly with Am 3+ than with Eu 3+ . EDA calculations showed that the attractive interaction between the molecular fragments exceeds the repulsive force, enhancing molecular stability. Thermodynamic calculations indicated that the selectivity coefficients of L H , L Et , L Br , and L Ca toward Am 3+ /Eu 3+ in water, n ‐butanol, and n ‐octanol were all more than 97%, with the separation factors ranged from 41.58 to 5.71 × 10 8 . The ligand L H was the most complexable with Am 3+ in n ‐octanol and had the greatest selectivity for Am 3+ /Eu 3+ separation in n ‐butanol, with the highest separation factor.