A Benchmark Comparison of σ/σ and π/π Dispersion: the Dimers of Naphthalene and Decalin, and Coronene and Perhydrocoronene

Abstract

Stacking interaction between π systems is a well recognized structural motif but stacking between σ systems was long considered of secondary importance. A recent paper points out that σ stacking can reach the energy of chemical bonds, and concludes that “σ/σ and π/π interactions are equally important” (Fokin, A. F.; Gerbig, D.; Schreiner, P. R., J. Am. Chem. Soc. 2011, 133, 20036). Our analysis shows that strong dispersion interaction requires rigid subsystems and a good fit of their repulsive potential walls, satisfied for both graphenes and larger graphanes (perhydrographenes). Comparison of the dimerization energies of decalin and perhydrocoronene with the naphthalene and coronene dimers at the Coupled Cluster (CC) CCSD(T) level confirms the substantial σ stacking energies in graphanes but gives lower binding energies than the B97D calculations of Fokin et al. Graphane dimerization energies are substantially lower at the CC level than the corresponding π stacking energies: the value for perhydrocoronene is only 67 % of the value for coronene, and the difference increases with system size. Our best estimate for the dimerization energy of naphthalene is 6.1 kcal/mol. Spin component scaled MP2 is unbalanced: it gives only 70 % of the CCSD(T) binding energy in σ dimers. The B3LYP D3 method compares very well with CC for both σ and π dimers at the van der Waals minimum but underestimates the binding at larger distances. We used the largest possible atomic basis for these systems with 64 bit arithmetic, half augmented pVDZ, and the results were corrected for basis set incompleteness at the MP2 level.

Theoretical study of stability and charge-transport properties of coronene molecule and some of its halogenated derivatives: A path to ambipolar organic-based materials?

“…81,82 As a matter of example, structures of coronene-type molecules are known to gain additional stabilization from C· · ·H interactions between molecules belonging to parallel planes (see Figure 7). Thus, we will concentrate in the following on the most stable arrangement of a pair of coronene molecules, from fully optimized BLYP-D3/def2-SVP calculations, which consists in a staggered stacking with the following displacements of the center of mass in the upper molecule with respect to that in the lower one alongside the in-plane (x, y) and perpendicular (z) axes described in for the (0, b, 0) dimer (central dimer of Figure 7) extracted from the unit cell (the X-ray structure of the coronene crystal was taken from the Crystallography Open Database and processed with the Mercury program 85 ); (v) the difference in the association energy on going from the cost-effective def2-SVP (−24.52 kcal mol −1 ) to the sufficiently large def2-TZVP basis set amounts to 3.7 kcal mol −1 , which thus forces the use of the latter in the following if one aims at estimating further association energies of nanoaggregates; and (vi) our results consistently agree with the findings recently reported in the literature [86][87][88][89][90][91][92] concerning relative molecular orientation and association energy. Since the crystal, or any other, structure data are not available for supramolecularly organised fluorinated derivatives, to the best of our knowledge, we will rely next on this level of theory (BLYP-D3/def2-TZVP) to analyse the stability of the rest of non-covalently bound molecules.…”

Compressed representation of dispersion interactions and long-range electronic correlations

“…This is in agreement with other literature findings. [60][61][62] We also verified that the relative contribution of σ and π electrons was well-represented by our approximate T disp 2 (see Supporting Information for a more detailed discussion).…”

Determining the cohesive energy of coronene by dispersion-corrected DFT methods: Periodic boundary conditions vs. molecular pairs

“…Upon inspection of Tables II and III, it can be immediately seen how the (0,b,0) dimer, which has been repeatedly studied in the literature by different theoretical methods, [87][88][89][90][91][92] is the structure contributing the most to the stability of the samples. We would like to emphasize how this energy gain is known to govern many interesting electronic properties of coronene samples, such as the anisotropic charge mobility values in organic electronic devices 93,94 or the thermochemistry of their spontaneous self-aggregation.…”