Faculty of Natural and Agricultural Sciences
Department of Chemistry
Theoretical/Computational Chemistry
Protonation constants of ligands containing biologically important donor atoms (such as N, O, or P) as well as stability constants of metal complexes with these ligands can usually be determined experimentally with high accuracy. Even though knowledge of these constants is of fundamental significance, it does not provide any information on sequence of protonation, or why some metal ions form stronger complexes than others, or why a small change in the ligand structure increases stability constants for some metal ions, but decreases for others, to mention just a few important questions. Theoretical prediction of dissociation constant (usually for molecules with one carboxylic group) throuth computational modeling utilizing a thermodynamic cycles is still generating values significantly different than experimental ones. Theoretical (computational) prediction of stability constants is much neglected. This is unfortunate because besides theoretically predicted thermodynamic constants one should gain additional information on many physical properties of as well as intramolecular interactions in molecules or complexes of interest. Our research is focused on the development of new methodologies (involving, besides thermodynamic cycles, isodesmic reactions) useful in theoretical/computational prediction of several consecutive protonation constants (for ligands containing different functional groups and donor atoms) as well as stability constants. Here, our ultimate aim is to achieve the agreement between computationally known values within a small fraction of a log unit. We also explore intra-molecular physical properties (by use of, for instance Bader's Atoms in Molecules theory and formalism, natural bond orbital analysis and second order perturbation energy) in order to theoretically predict sequence of protonation reactions, or to discover properties that control the strength of complexes formed. We also attempt the development of methodologies that should allow theoretical prediction the mechanism of complexation reaction.
|
