Chemical concepts from Density Functional Theory:
Application to molecular mechanochemistry
Frank de PROFT
Research Group of General Chemistry (ALGC), Vrije Universiteit Brussel (VUB), Brussels, Belgium
Jeudi 14 Novembre 2019, 11h00
bibliothèque LCT, tour 12 - 13, 4ème étage
Accelerating a chemical reaction is of fundamental importance for the experimental chemist. Supplying heat, light or electricity to the reactant (mixture) leads to standard techniques in thermochemistry, photochemistry and electrochemistry. A fourth way of chemical activation, consisting in supplying mechanical energy to the reactant system, termed mechanochemistry, is less well known [1,2]. According to IUPAC's golden book [3], a mechanochemical reaction is a "chemical reaction induced by the direct absorption of mechanical energy". In the last two decades molecular mechanochemistry has come to the forefront [1,4].
Density Functional Theory is a well-suited theory for the introduction of chemical concepts, also known as reactivity indices [5]. These are introduced as response functions of the energy E of the system with respect to either the number of electrons N, the external potential ν(r) or both. These definitions have afforded the non-empirical calculation of the reactivity indices and applications in many fields of chemistry have been studied.
In this contribution, the E = E[N,ν(r)] functional is expanded as to include the external mechanical force to E[N,ν(r),Fext], which allows for the quantification of the global as well as local reactivity of molecules that are subjected to an external force [6].
In a first part of the lecture, applications to a series of diatomic molecules are discussed [6]. Next, the effect of applied bending forces in 2-butyne fragments was investigated as a model for strained cyclic alkynes, an important class of molecules for in vitro applicable click-reactions [7]. The local softness of the triple bond with an applied external force revealed interesting changes in its chemical reactivity in line with the reactivity observed in strain promoted alkyne-azide couplings.
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References :
[1] T. Stauch and A. Dreuw, Chem. Rev. 116 (2016) 14137.
[2] J. Ribas-Arino and D. Marx, Chem. Rev. 112 (2012) 5412.
[3] A. D. Mc. Naught and A. Wilkinson, IUPAC Compendium of Chemical Technology (the Gold Book), 2nd Edition, Blackwell Scientific Publication, Oxford, UK (1997).
[4] L. Tackacks, Chem. Soc. Rev. 42 (2013) 7649.
[5] (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 (1995) 701. (c) H. Chermette, J. Comput. Chem. 20 (1999) 129. (d) P. Geerlings, F. De Proft and W. Langenaeker, Chem. Rev. 103 (2003) 1793. (e) P. W. Ayers, J. S. M. Anderson and L. J. Bartolotti, Int. J. Quant. Chem. 101 (2005) 520.
[6] T. Bettens, M. Alonso, P. Geerlings and F. De Proft, Phys. Chem. Chem. Phys. 21, (2019) 7378.
[7] T. Bettens, M. Alonso, P. Geerlings and F. De Proft, in preparation.