Comparative analysis of the performance of commonly available density functionals in the determination of geometrical parameters for zinc complexes

A set of 44 Zinc-ligand bond-lengths and of 60 ligand-metal-ligand bond angles from 10 diverse transition-metal complexes, representative of the coordination spheres of typical biological Zn systems, were used to evaluate the performance of a total of 18 commonly available density functionals in geometry determination. Five different basis sets were considered for each density functional, namely two all-electron basis sets (a double-zeta and triple-zeta formulation) and three basis sets including popular types of effective-core potentials: Los Alamos, Steven-Basch-Krauss, and Stuttgart-Dresden. The results show that there are presently several better alternatives to the popular B3LYP density functional for the determination of Zn-ligand bond-lengths and angles. BB1K, MPWB1K, MPW1K, B97-2 and TPSS are suggested as the strongest alternatives for this effect presently available in most computational chemistry software packages. In addition, the results show that the use of effective-core potentials (in particular Stuttgart-Dresden) has a very limited impact, in terms of accuracy, in the determination of metal-ligand bond-lengths and angles in Zinc-complexes, and is a good and safe alternative to the use of an all-electron basis set such as 6-31G(d) or 6-311G(d,p).