Cation-π interactions in competition with cation microhydration: a theoretical study of alkali metal cation-pyrene complexes.
Cation-π interactions were systematically investigated for the adsorption of H+and alkali metal cations M+to pyrene by means of Møller-Plesset perturbation theory (MP2) and density functional theory (DFT). The main aims were to determine the preferred adsorption sites and how the microhydration shell influences the adsorption process. The preferred adsorption sites were characterized in terms of structural parameters and energetic stability. Stability analysis of the M+-pyrene complexes revealed that the binding strength and the barrier to transitions between neighboring sites generally decreased with increasing cation size from Li+to Cs+. Such transitions were practically barrierless (<<1 kcal/mol) for the large Rb+and Cs+ions. Further, the influence of the first hydration shell on the adsorption behavior was investigated for Li+and K+as representatives of small and large (alkali metal) cations, respectively. While the isolated complexes possessed only one minimum, two minima-corresponding to an inner and an outer complex-were observed for microhydrated complexes. The small Li+ion formed a stable hydration shell and preferentially interacted with water rather than pyrene. In contrast, K+favored cation-π over cation-water interactions. It was found that the mechanism for complex formation depends on the balance between cation-π interactions, cation-water complexation, and the hydrogen bonding of water to the π-system.
Institute for Theoretical Chemistry, University of Vienna, Währinger Strasse 17, 1090, Vienna, Austria.
Hasan
H
Pašalić
School of Pharmaceutical Sciences and Technology, Tianjin University, 92 Weijin Road, Nankai District, Tianjin, 300072, People's Republic of China.|Institute for Soil Research, University of Natural Resources and Life Sciences Vienna, Peter-Jordan-Strasse 82, 1190, Vienna, Austria.
Adelia J A
AJ
Aquino
Institute for Soil Research, University of Natural Resources and Life Sciences Vienna, Peter-Jordan-Strasse 82, 1190, Vienna, Austria. daniel.tunega@boku.ac.at.
Daniel
http://orcid.org/0000-0003-0822-1580
D
Tunega
Institute for Soil Research, University of Natural Resources and Life Sciences Vienna, Peter-Jordan-Strasse 82, 1190, Vienna, Austria.
Georg
G
Haberhauer
Institute for Soil Research, University of Natural Resources and Life Sciences Vienna, Peter-Jordan-Strasse 82, 1190, Vienna, Austria.
Martin H
MH
Gerzabek
Institute for Theoretical Chemistry, University of Vienna, Währinger Strasse 17, 1090, Vienna, Austria. hans.lischka@univie.ac.at.|School of Pharmaceutical Sciences and Technology, Tianjin University, 92 Weijin Road, Nankai District, Tianjin, 300072, People's Republic of China. hans.lischka@univie.ac.at.
Hans
H
Lischka
Alkali metal cation–pyrene; Cation–π interactions; DFT; Microhydration