Prampolini G, d'Ischia M, Ferretti A. The phenoxyl group-modulated interplay of cation-π and σ-type interactions in the alkali metal series.
Phys Chem Chem Phys 2020;
22:27105-27120. [PMID:
33225336 DOI:
10.1039/d0cp03707a]
[Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023]
Abstract
The interaction potential energy surfaces (IPESs) of four alkaline metal cations (Na+, K+, Rb+ and Cs+) complexed with phenol and catechol were explored by accurate ab initio calculations to investigate the interplay of different noncovalent interactions and their behavior along the alkali metal series and upon -OH substitution. Selected one-dimensional interaction energy curves revealed two different minimum energy configurations for all phenol- and catechol-metal complexes, characterized either by cation-π or σ-type interactions. For each investigated complex several two-dimensional IPES maps were also computed, exploiting the computational advantages of the MP2mod approach. The size of the alkali cation was found to play a similar role in modulating both kinds of complexes, as the interaction strength always decreases along the metal series, from Na+ to Cs+. Conversely, the number of hydroxyl substituents markedly affected cation-π complexes vs. σ-type ones. As a most relevant finding, in catechol-metal complexes the strength of cation-π interactions is around half that of the σ-type ones. It is argued that the combined effect of cation dimensions and hydroxyl substitution in catechol-Na+ complexes makes σ-type configurations remarkably more stable and easily accessible than cation-π ones. Besides shedding new light on the origin of biological phenomena connected with underwater adhesion, the quantum mechanical interaction energy database provided herein may offer a useful reference for tuning accurate force fields, suitable for molecular dynamics simulations, where environmental effects might be also taken into account.
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