Modeling lanthanide coordination compounds: Sparkle/AM1 parameters for praseodymium (III)

The Sparkle/AM1 model, recently defined for Eu(III), Gd(III) and Tb(III) [R.O. Freire, G.B. Rocha, A.M., Simas, Inorg. Chem. 44 (2005) 3299] is now extended to Pr(III), using the same parameterization scheme. Thus, a set of 15 complexes, with various representative ligands of high crystallographic quality (R-factor < 0.05 Å) and which possess oxygen and/or nitrogen as coordinating atoms, was used as the training set. In the validation procedure we used a set of 33 more structures, also of high crystallographic quality. For the 48 complexes, the Sparkle/AM1 unsigned mean error, for all interatomic distances between the Pr(III) ion and the ligand atoms of the first sphere of coordination, is 0.08 Å, again comparable to present day ab initio/ECP calculations, while being hundreds of times faster.