Nature of Noncovalent Interactions in Catenane Supramolecular Complexes: Calibrating the MM3 Force Field with ab Initio, DFT, and SAPT Methods

Abstract

The design and assembly of mechanically interlocked molecules, such as catenanes and rotaxanes, are dictated by various types of noncovalent interactions. In particular, [C-H⋯O] hydrogen-bonding and π-π stacking interactions in these supramolecular complexes have been identified as important noncovalent interactions. With this in mind, we examined the [3] catenane 2·4PF6 using molecular mechanics (MM3), ab initio methods (HF, MP2), several versions of density functional theory (DFT) (B3LYP, M0X), and the dispersion-corrected method DFT-D3. Symmetry adapted perturbation theory (DFT-SAPT) provides the highest level of theory considered, and we use the DFT-SAPT results both to calibrate the other electronic structure methods, and the empirical potential MM3 force field that is often used to describe larger catenane and rotaxane structures where [C-H⋯O] hydrogen-bonding and π-π stacking interactions play a role. Our results indicate that the MM3 calculated complexation energies agree qualitatively with the energetic ordering from DFT-SAPT calculations with an aug-cc-pVTZ basis, both for structures dominated by [C-H⋯O] hydrogen-bonding and π-π stacking interactions. When the DFT-SAPT energies are decomposed into components, and we find that electrostatic interactions dominate the [C-H⋯O] hydrogen-bonding interactions while dispersion makes a significant contribution to π-π stacking. Another important conclusion is that DFT-D3 based on M06 or M06-2X provides interactions energies that are in near-quantitative agreement with DFT-SAPT. DFT results without the D3 correct have important differences compared to DFT-SAPT while HF and even MP2 results are in poor agreement with DFT-SAPT.

Recent developments in symmetry‐adapted perturbation theory

“…As far as cluster models of the liquid phase are concerned, SAPT has been applied to elucidate the origins of interactions involving ionic liquids 50,[239][240][241][242] and to understand the π − π stacking occurring in an organic solvent. 243 Besides the endohedral fullerenes mentioned earlier, the SAPT and SAPT(DFT) energy decompositions have been applied to other supramolecular complexes including catenanes, 244 porphyrins and metalloporphyrins, 245 and the cucurbit [7]uril macrocycle. 246 SAPT0 has been used to decompose interaction energies of dimers relevant to organic electronics 247 ; in particular, it has been proposed to improve electronic couplings via an enhancement of charge penetration brought about by incorporating large heteroatoms in π-conjugated cores.…”

Cryptophanes for Methane and Xenon Encapsulation: A Comparative Density Functional Theory Study of Binding Properties and NMR Chemical Shifts

“…35 The conformational freedom of the methoxy and methyl substituents was thoroughly analysed by running calculations using ɷB97X-D/6-31G(d). After this analysis, the most stable structures were used for further geometry optimizations and frequency calculations using the 37,38 We used the functionals ɷB97X-D, 33 B3LYP, [39][40][41] B3LYP-D3, [39][40][41][42] B3LYP-D3BJ [39][40][41][42] and M06-L 43 in this study. Previous studies of host-guest complexes have indicated that SCS-MP2 better predicts the change in energies of complexes with weak non-covalent interactions 38,44,45 compared to other commonly used DFT functionals.…”

Theoretical investigation of a cation‐controllable molecular shuttle of tetracationic cyclophane

“…where the total energy of the molecular switch system is described by E complex and E thread and E macrocycle refers to the energy of the isolated monomers . The E b values imply binding interactions between different recognition sites and the macrocycle.…”