An ab initio take on dispersion in σ-alkane complexes Carlos Martín Fernández, M. Arif Sajjad, S. A. Macgregor Heriot-Watt University, UK
Amongst the many tools that have been developed for the analysis of non-covalent interactions [1], Energy Decomposition Analyses (EDAs) have proven to be of great use. Nonetheless, the different flavours of EDAs can show some differences in the way that the energy is partitioned, and so might provide different answers to the same problem. Other important issues have to do with the level of theory at which the energy terms are calculated and with the ability of the EDA to cover from weak to strong interactions [2]. Recently, a local energy decomposition analysis (LED) based on the DLPNO-CCSD(T) method has been developed and applied to a wide range of systems [3, 4]. Importantly, this method uses energies calculated at a high level of theory and can describe interactions at any range from the weak-strong continuum. Moreover, it can provide a formally well-founded definition of all the different terms in the energy partition, which is particularly interesting regarding its description of London dispersion contributions.
Figure 1 . The two σ-alkane complexes under study, highlighting the interaction with one of the six neighbouring [BAr F 4 ] anions. Note the widely different stabilities. In this work, we will apply such LED analysis to two important σ-alkane complexes (Fig. 1) that have been thoroughly characterized both experimentally and with the aid of computational tools [5-7]. Previously, intramolecular interactions between the NBA (norbornane, C 7 H 12 ) and the {RhP 2 } fragment in [1-NBA] + have been assessed with LED methods [8]. Here we consider intermolecular non-covalent interactions between the cations and the surrounding anions, thus taking into account the effect of the crystal environment. Due to the large system size, special attention will be paid to the details of the calculation in order to yield both accurate and meaningful results. References 1. E.Pastorczak and C. Corminboeuf, J. Chem. Phys. 2017 , 146 , 120901. 2. J.Andrés, P. W. Ayers, R. A. Boto et al. J. Comput. Chem . 2019 , 40 , 2248–2283. 3. G.Bistoni, WIREs Comput Mol Sci . 2020 , 10 , e1442. 4. W.B. Schneider, G. Bistoni, M. Sparta, et al. J. Chem. Theory Comput., 2016 , 12 , 4778–4792.
5. S.D. Pike, A. L. Thompson, A. G. Algarra, et al. Science 2012 , 337 , 1648–1651. 6. A.G. Algarra, A. L. Burnage, M. Iannuzzi, et al. Struct. Bond. , 2020 , 186 , 183–228. 7. A.J. Bukvic, A. L. Burnage, G. J. Tizzard, et al. J. Am. Chem. Soc. 2021 , 143 , 5106–5120. 8. Q. Lu, F. Neese and G. Bistoni, Phys. Chem. Chem. Phys. , 2019 , 21 , 11569–11577.
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