Modeling rare earth complexes: Sparkle/PM3 parameters for thulium(III)

The Sparkle model, recently defined for Tm(III) within AM1 [R.O. Freire, G.B. Rocha, A.M. Simas, Chem. Phys. Lett. 411 (2005) 61], is now extended to PM3. The Sparkle/PM3 unsigned mean error, for all interatomic distances between the Tm(III) ion and the directly coordinating oxygen or nitrogen atoms, is 0.08Å, a level of accuracy equivalent to the Sparkle/AM1 figure of 0.07Å, as well as to results from present day ab initio effective core potential calculations.