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

Abstract

In this manuscript, we use the primary source of geometrical information, i.e., Cambridge Structural Database (CSD), combined with density functional theory (DFT) calculations (PBE0-D3/def2-TZVP level of theory) to demonstrate the relevance of π-hole interactions in para-nitro substituted pyridine-1-oxides. More importantly, we show that the molecular electrostatic potential (MEP) value above and below the π–hole of the nitro group is largely influenced by the participation of the N-oxide group in several interactions like hydrogen-bonding (HB) halogen-bonding (XB), triel bonding (TrB), and finally, coordination-bonding (CB) (N+–O− coordinated to a transition metal). The CSD search discloses that p-nitro-pyridine-1-oxide derivatives have a strong propensity to participate in π-hole interactions via the nitro group and, concurrently, N-oxide group participates in a series of interactions as electron donor. Remarkably, the DFT calculations show from strong to moderate cooperativity effects between π–hole and HB/XB/TrB/CB interactions (σ-bonding). The synergistic effects between π-hole and σ-hole bonding interactions are studied in terms of cooperativity energies, using MEP surface analysis and the Bader’s quantum theory of atoms in molecules (QTAIM).

Comparative Structural Study of Three Tetrahalophthalic Anhydrides: Recognition of X···O(anhydride) Halogen Bond and πh···O(anhydride) Interaction

“…The strength and nature of interactions were investigated for the most relevant contacts (C–X···O (acyl or anhydride) and C–X···X, where X is a halogen atom) by a number of theoretical methods: the molecular electrostatic potential (MEP) [ 27 , 28 ], the quantum theory of atoms in molecules (QTAIM) [ 29 , 30 , 31 ], the independent gradient model (IGMH) [ 32 , 33 , 34 , 35 , 36 ], natural bond orbital (NBO) [ 37 ] analyses, the electron density difference (EDD) [ 38 , 39 ], and the symmetry-adapted perturbation theory (SAPT) [ 40 , 41 , 42 , 43 , 44 ]. We have already successfully used these methods for a detailed study of halogen bonds [ 45 ].…”

“…The MEP surface is important to understand the nature of noncovalent interactions regulated by electrostatic effects [ 27 , 28 ]. On the MEP surface of tetrahalophthalic anhydrides ( Figure 5 ), two regions of positive electrostatic potential known as π-holes were observed due to the electron-withdrawing effect of the halogen and oxygen atoms [ 28 ]. In this case, the positive potential of the five-membered ring was larger and insignificantly changed from halogen substituents.…”

The Physical Chemistry and Chemical Physics (PCCP) Section of the International Journal of Molecular Sciences in Its Publications: The First 300 Thematic Articles in the First 3 Years

“…This direction is represented by 39 articles [ 28 , 35 , 129 , 134 , 136 , 190 , 191 , 192 , 193 , 194 , 195 , 196 , 197 , 198 , 199 , 200 , 201 , 202 , 203 , 204 , 205 , 206 , 207 , 208 , 209 , 210 , 211 , 212 , 213 , 214 , 215 , 216 , 217 , 218 , 219 , 220 , 221 , 222 , 223 ]. Their distribution, according to the above types, is presented in Table 7 .…”

Molecular structure and electron distribution of 4-nitropyridine N-oxide: Experimental and theoretical study of substituent effects

“…As we can see the simple electrostatic model which employing the Bader's atomic charges of free 4-NO 2 -PyO molecule allows describing correctly the arrangement of these molecules inside the crystal. Galm es B. et al [54] had attempted to characterize the geometric features of the nitropyridine-1-Oxides complexes employing the molecular electrostatic potential and results of QTAIM. The position of 4-NO 2 -PyO molecules in the crystal pack has been described as interaction between р-hole donor nitro group of one molecule and oxygen atom of N/O semipolar bond of another.…”