title: Computing pK(A) values of hexa-aqua transition metal complexes.
abstract: Aqueous pKA values for 15 hexa-aqua transition metal complexes were computed using a combination of quantum chemical and electrostatic methods. Two different structure models were considered optimizing the isolated complexes in vacuum or in presence of explicit solvent using a QM/MM approach. They yield very good agreement with experimentally measured pKA values with an overall root mean square deviation of about 1 pH unit, excluding a single but different outlier for each of the two structure models. These outliers are hexa-aqua Cr(III) for the vacuum and hexa-aqua Mn(III) for the QM/MM structure model. Reasons leading to the deviations of the outlier complexes are partially explained. Compared to previous approaches from the same lab the precision of the method was systematically improved as discussed in this study. The refined methods to obtain the appropriate geometries of the complexes, developed in this work, may allow also the computation of accurate pKA values for multicore transition metal complexes in different oxidation states.
authors.affiliation: Department of Biology, Chemistry and Pharmacy, Institute of Chemistry and Biochemistry, Freie Universität Berlin, Fabeckstr. 36a, D-14195, Berlin, Germany.
authors.forename: Gegham
authors.initials: G
authors.lastname: Galstyan
authors.forename: Ernst-Walter
authors.initials: EW
authors.lastname: Knapp
mesh_terms: D002857:Chromium / Q000737:chemistry*; D056831:Coordination Complexes / Q000737:chemistry*; D008345:Manganese / Q000737:chemistry*; D008958:Models, Molecular; D015394:Molecular Structure; D011789:Quantum Theory; D055672:Static Electricity; D014867:Water
chemical_list: D056831:Coordination Complexes; D014867:Water; D002857:Chromium; D008345:Manganese
keywords: gas-phase basicity; hexa-aqua transition metal complexes; hydrolysis constants; pKA; solvation energy