A theoretical study on the coordination behavior of some phosphoryl, carbonyl and sulfoxide derivatives in lanthanide complexation.

The selectivity of phosphoryl P(O)R3, sulfoxide S(O)R2, and carbonyl C(O)R2 (R = NH2, CH3, OH, and F) derivatives with lanthanide cations (La3+, Eu3+, Lu3+) was studied by density functional theory calculations. Theoretical approaches were also used to investigate energy and the nature of metal-ligand interaction in the model complexes. Atoms in molecules and natural bond orbital (NBO) analyses were accomplished to understand the electronic structure of ligands, L, and the related complexes, L-Ln3+. NBO analysis demonstrated that the negative charge on phosphoryl, carbonyl, and sulfoxide oxygen (OP, OC, and OS) has maximum and minimum values when the connected -R groups are -NH2 and -F. The metal-ligand distance declines as, -F > -OH > -CH3 > -NH2. Charge density at the bond critical point and on the lanthanide cation in the L-Ln3+ complexes varies in the order -F < -OH < -CH3 < -NH2, due to greater ligand to metal charge transfer, which is well explained by energy decomposition analysis. It was also illustrated that E(2) values of Lp(N) → σ*(Y-N) vary in the order P=O ˃ S=O ˃ C=O and the related values of Lp(N) → σ*(Y=O) change as C=O ˃ S=O ˃ P=O in (NH2)nYO ligands (Y = P, C, and S). Trends in the L-Ln3+ CP-corrected bond energies are in good accordance with the optimized OY⋯Ln distances. It seems that, comparing the three types of ligands studied, NH2-substituted are the better coordination ligands. Graphical Abstract Density functional theory (B3LYP) calculations were used to compare structural, electronic and energy aspects of lanthanide (La, Eu, Lu) complexes of phosphine derivatives with those of carbonyls and sulfoxides in which the R- groups connected to the P=O, C=O and S=O are -NH2, -CH3, -OH and -F.