Topological Approaches to Intermolecular Interactions

26-28 June 2013 - Paris

Workshop on "Topological approaches to intermolecular interactions"

Combined use of DFT based Reactivity Indices and the Non-covalent Index in the Study of Intermolecular Interactions

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Conceptual Density Functional Theory (sometimes also called DFT based reactivity theory or Chemical DFT) has proven to be an ideal framework for the introduction of chemical reactivity descriptors [1]. These indices are defined as response functions of the energy E of the system with respect to either the number of electrons N, the external potential v(r) or both. These definitions have afforded their non-empirical calculation and applications in many fields of chemistry have been performed, often combined with principles such as the electronegativity equalization principle of Sanderson and Pearson’s hard and soft acids and bases (HSAB) and maximum hardness principles. In this talk, we focus on recent studies in which a combined use of these reactivity indices and the Non-Covalent Interaction (NCI) Index [2] was carried out in order to scrutinize intermolecular interactions. In a first part, we focus on halogen bonding. Halogen bonds between the trifluoromethyl halides CF3Cl, CF3Br and CF3I, and dimethyl ether, dimethyl sulfide, trimethylamine and trimethyl phosphine were investigated using the HSAB concept with conceptual DFT reactivity indices, the Ziegler-Rauk type energy decomposition analysis [3], the Natural Orbital for Chemical Valence framework (NOCV) [4], and the NCI index. It is found that the relative importance of electrostatic and orbital (charge transfer) interactions in these halogen bonded complexes varies as a function of both the donor and acceptor molecules [5]. Hard and soft interactions were distinguished and characterized by atomic charges, electrophilicity and local softness indices. Dual descriptor plots indicate an orbital σ-hole on the halogen similar to the electrostatic σ-hole manifested in the molecular electrostatic potential. The characteristic signal found in the reduced density gradient versus electron density diagram corresponds to the non-covalent interaction between contact atoms in the NCI plots, which is the manifestation of halogen bonding within the NCI theory. The unexpected C–X bond strengthening observed in several cases was rationalized within the MO framework.

In a second part of the talk, we present recent results on the use of the above mentioned quantities in the study of metal-metal interactions [6].

[1] (a) R. G. Parr and W. Yang, Density Functional Theory of Atoms and Molecules, Oxford University Press, New York, 1989. (b) R. G. Parr and W. Yang, Ann. Rev. Phys. Chem. 46, 701 (1995). (c) H. Chermette, J. Comput. Chem. 20, 129 (1999). (d) P. Geerlings, F. De Proft and W. Langenaeker, Chem. Rev. 103, 1793 (2003). (e) P. W. Ayers, J. S. M. Anderson and L. J. Bartolotti, Int. J. Quant. Chem. 101, 520 (2005).
[2] (a) E. R. Johnson, S. Keinan, P. Mori-Sanchez, J. Contreras-Garcia, A. J. Cohen and W. T. Yang, Journal of the American Chemical Society 132, 6498 (2010). (b) J. Contreras-Garcia, E. R. Johnson, S. Keinan, R. Chaudret, J. P. Piquemal, D. N. Beratan and W. T. Yang, J. Chem. Theor. Comput. 7, 625 (2011).
[3] (a) F. M. Bickelhaupt and E. J. Baerends, Reviews in Computational Chemistry, 15, 1 (2000); (b) T. Ziegler and A. Rauk, Theoretica Chimica Acta 46, 1 (1977).
[4] M. P. Mitoraj, A. Michalak and T. Ziegler, J. Chem. Theor. Comput. 5, 962 (2009).
[5] B. Pinter, N. Nagels, W. A. Herrebout and F. De Proft, Chem. Eur. J. 19, 518 (2013).
[6] B. Pinter, L. Broeckaert, J. Turek, A. Růžička and F. De Proft, in preparation.

Speaker(s) : Frank De Proft, Eenheid Algemene Chemie (ALGC), Vrije Universiteit Brussel (VUB), Pleinlaan 2, B-1050 Brussels, Belgium
Public : Tous
Date : June 26 2013
Place : Paris