Theoretical ab Initio Study on Cooperativity Effects between Nitro π‐hole and Halogen Bonding Interactions

Abstract

This article analyzes the interplay between nitro's π‐hole and halogen–bonding (XB) interactions in nitroarenes. Remarkable cooperativity effects are observed when π–hole and XB interactions coexist in the same complex. The nitroarene presents two π‐holes, one approximately over the N atom of the nitro group and the other over the aromatic ring, being the former more positive. The interplay between both interactions has been analyzed in terms of energetic and geometric features of the complexes, which are computed at the RI‐MP2/def2‐TZVPD level of theory. Molecular electrostatic potential (MEP) surface calculations have been used to explore the variation of the MEP values at the π‐hole upon the formation of halogen bonding interactions between the nitroarene and CF3X (X=Cl, Br and I) molecules. In addition, the Bader's theory of atoms in molecules” (AIM) is used to characterize the interactions by means of the distribution of bond critical points and bond paths and to analyze their strengthening or weakening depending upon the variation of charge density at critical points. The aforementioned computational methods are adequate to examine how these interactions mutually influence each other. Natural bond orbital (NBO) and noncovalent interaction plot (NCIPlot) computational tools have been also used in some representative complexes to further analyze cooperativity effects. Finally, the Cambridge Structural Database (CSD) is used to provide some experimental evidence.

Versatility of the Cyano Group in Intermolecular Interactions

“…The same sort of tetrel bonding through a C π-hole occurs in other systems as well [ 32 , 33 ]. This idea is not restricted to C but occurs on other sorts of atoms—for example, the S atom of SO 2 [ 31 ] or SO 3 [ 34 ] or the central O of ozone [ 35 ] or for tetrel T atoms larger than C, as in F 2 TO [ 36 , 37 , 38 ], or the N atom of the -NO 2 group [ 39 ]. Other planar examples involve triel (Tr) atoms in TrR 3 , where R indicates some substituent [ 40 , 41 ].…”

Nitropyridine-1-Oxides as Excellent π-Hole Donors: Interplay between σ-Hole (Halogen, Hydrogen, Triel, and Coordination Bonds) and π-Hole Interactions

“…The values of the electron charge density ρ(r) and its Laplacian [∇ 2 ρ(r)] measured at the bond critical points (CPs) that emerge upon complexation give information on the strength of noncovalent interaction as previously shown in the literature. In fact, the values of ρ(r) have been used before to analyze cooperativity effects in several multicomponent systems [64,65,66,67,68,69]. For instance, the ρ(r) and ∇ 2 ρ(r) values for the σ-complexes clearly correlate (see Table 2) well with the interaction energies and equilibrium distances.…”

“…As commented above, we have previously studied cooperativity effects between π-hole and halogen bonding interactions in p-nitropyridine and p-nitrobenzonitrile compounds [69]. In their ternary complexes with Lewis bases and halogen bond donors the reported cooperativity energies ranged from –4.6 kcal mol −1 for anionic donors and strong electron acceptors (CF 3 I) to –0.1 kcal mol −1 for weak donors (CO) and acceptors (CF 3 Cl).…”

“…We and others have demonstrated both experimentally and theoretically important cooperativity effects in complexes where two or more noncovalent interactions coexist [63,64,65,66,67,68]. Moreover, we have recently analyzed cooperativity effects between π-hole and halogen bonding interactions in 4-nitropyridine and 4-cyano-nitrobenzene [69], without experimental support from the CSD. In this new work, we report a combined theoretical density functional theory (DFT) and CSD study where the interplay between π–hole and several σ-hole interactions are analyzed.…”

Supramolecular Assemblies in Pb(II) Complexes with Hydrazido-Based Ligands

“…A careful inspection of the structure shows that the interaction of perchlorate anion with the ligand is ditopic. That is, one O-atom is over the coordinated pyridine ring of the nicotine moiety and another one with shortest distance (3.08 Å, see Figure 10) is located over the C atom of the hydrazido group (π-hole interaction) [58,59]. This C atom is a good π-hole donor [60] due to the adjacent Pb-O coordination bond that enhances the π-acidity of C. We have computed the interaction energy of the model shown in Figure 10a, which is very large (∆E 1 = −173.9 kcal/mol) because of the significant electrostatic attraction between the dicationic [Pb 2 (L 1 ) 4 (NO 3 ) 2 ] 2+ moiety and the anions.…”