Publication details

On the Non-Classical Contribution in Lone-Pair-pi Interaction: IQA perspective

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Year of publication 2015
Type Article in Periodical
Magazine / Source Physical Chemistry Chemical Physics
MU Faculty or unit

Central European Institute of Technology

Web DOI: 10.1039/C5CP04489H
Field Physical chemistry and theoretical chemistry
Keywords interaction energy; LP-pi; IQA; QTAIM; exchange-correlation
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Description In the present work the nature of lone-pair–pi interactions between water molecules and a number of pi-rings with different substituents/hetero-atoms in the light of quantum chemical topology approaches is studied. The Quantum Theory of Atoms in Molecules (QTAIM) and Interacting Quantum Atoms (IQA) were employed for distinguishing the role of heteroatoms and electron withdrawing substituents in the complex formation between water and pi-rings. Our IQA study identified three classes of water–pi complexes on the basis of the relative role of electrostatics (classical) and exchange–correlation (non-classical) factors in the interaction energy between the oxygen of water (the lone-pair donor) and the sp2 atoms of the pi-ring, i.e. the primary lp–pi interaction. Considering both the primary and secondary (the rest of interatomic interactions except Owater–pi-ring atoms) interactions demonstrates that the exchange–correlation is the dominant contributor to the binding energy. This proves a non-negligible contribution of non-classical factors in the stabilization of the lone-pair–pi complexes. However, in spite of a relatively large contribution of the exchange–correlation, this part of the interaction energy is virtually counterbalanced by the deformation energy, i.e. the increase in atomic kinetic energy upon complexation. This finding clarifies why water–pi interactions can be modelled by simple electrostatics without the need to invoke quantum effects.
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