Shedding Light on the Nature of Host–Guest Interactions in PAHs-ExBox⁴⁺ Complexes

Abstract

Host-Guest systems formed by polycyclic aromatic hydrocarbons and ExBox 4+ are suitable models to gain a deeper understanding in π-π interactions, which are fundamental in supramolecular chemistry. The physical nature of Host-Guest (HG) interactions between ExBox 4+ (1) and polycyclic aromatic hydrocarbons (PAHs) (2-12) is investigated at the light of the energy decomposition (EDA-NOCV), non-covalent interactions (NCI), and magnetic response analyses. The EDA-NOCV results show that the dispersion forces play a crucial role on the HG interactions in PAHs⊂ExBox 4+ complexes. The HG interaction energies are dependent on both, the size of the PAH employed and the number of π-electrons in the guest molecules. The parallel face-toface arrangement between HG aromatic moieties is also fundamental to maximize the dispersion interaction and consequently for the attractive energy which leads to the inclusion complex formation.

The ability of Ex2Box4+ to interact with guests containing π‐electron‐rich and π‐electron‐poor moieties

“…It has been demonstrated that 1 is able to form HG compounds with eleven different PAHs, acting as phase catalyst delivering PAHs from crude oil to aqueous milieu, as well as scavenging PAHs from aqueous media . The physical nature of the HG interactions between 1 and PAHS was previously elucidated by us …”

“…In our previous study, we have showed that 1 is able to interact with guests of different volumes by adjusting its geometry to maximize the π‐π stacking. Concerning the physical nature of HG interactions, EDA‐NOCV results revealed that dispersion forces modulate the interactions between 1 and PAHs (all π‐electron‐rich guests), constituting 60% of the attractive interactions, while the remaining contributions are 25%‐27% electrostatic and 15%‐13% orbital, which does not confirm the argument stated in the synthesis paper that charge transfers from guest to host occurs, leading to interactions essentially electrostatic.…”

Adsorption of polycyclic aromatic hydrocarbons and inversion barriers of curved conjugated systems inside the molecular cage ExCage6+

“…On encapsulation, the inversion barrier is reduced by 2.09 ± 0.72 kcal/mol. This receptor has been the subject of theoretical studies which investigated the encapsulation of PAH and its performance as a gas storage material . The study by Nagurniak et al demonstrated that dispersion interactions play a crucial role in the PAH‐ExBox 4+ .…”

“…This receptor has been the subject of theoretical studies which investigated the encapsulation of PAH and its performance as a gas storage material . The study by Nagurniak et al demonstrated that dispersion interactions play a crucial role in the PAH‐ExBox 4+ . In the same vein, Ulloa et al showed that dispersion interactions are of utmost importance to study the interaction between the receptor cyclobis(paraquat‐p‐pheny‐lene) (CBPQT 4+ ) and tetrathiafulvalene while the inclusion of counterions has a strong effect on the computed interactions energies.…”

Advances in bonding and properties of inorganic systems from relativistic calculations in Latin America

“…In addition, several host‐guest studies of lighter elements have been carried out involving the ExBox 4+ , Ex 2 Box 4+ , and CBPQT 4+ by Nagurniak and Ulloa, and the noncovalent character of hydrogen‐bond strength on triple AAA‐DDD arrays, has also been accounted for. On the other hand, Claveria‐Cádiz has proposed a series of Keggin heteropolyanions containing fifth period main group heteroatoms, [XM 12 O 40 ] n ‐ (X = Sn(IV), Sb(V) and Te(VI); M = Mo and W; n = 2,3,4), where a detailed energy decomposition analysis of the {XO 4 }‐{M 12 O 36 } interaction shows the existence of a predominant ionic character …”