RM1 modeling of neodymium, promethium, and samarium coordination compounds†
The RM1 model is parameterized for the prediction of geometries of Nd(III), Sm(III), and Pm(III) complexes. By adding the lanthanides to RM1 with a set of 5d, 6s, and 6p orbitals, the model is now capable of accurately describing direct coordination to the lanthanide trication, not only by oxygen and nitrogen, but also by other atoms, such as carbon, sulfur, chlorine and bromine. Overall, the accuracy of the RM1 model for interatomic distances between the lanthanide ion and other directly coordinated atoms is 0.06 Å for both Nd(III) and Sm(III), and 0.05 Å for Pm(III). The RM1 model for Nd(III), Sm(III), and Pm(III) is indeed a more general model than the previous sparkle models, and may be used for any complex of these trivalent lanthanide ions. More importantly, if the Nd(III), Sm(III), or Pm(III) complex of interest contains coordinated atoms which are neither oxygen nor nitrogen, then the RM1 model advanced in this article must be the semiempirical model of choice.